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The Great Fever | Article

In the 20th century, a vaccine for yellow fever was developed to protect people in regions where the disease still flourishes. Epidemics continued, however, during every decade of the century, and cases still surface to the present time.

The Panama Canal
Soon after the discovery that mosquitoes transmit yellow fever, Major William Crawford Gorgas put the information to work in Cuba and later in the Panama Canal Zone. A previous French attempt to build the canal ended in disaster when disease, particularly yellow fever and malaria, incapacitated thousands of project workers. Gorgas, the sanitation chief in Cuba during the U.S. occupation, fumigated against mosquitoes and rid the area of standing water, leading to a healthy workforce and successful project. But while the opening of the Panama Canal in 1914 eased travel throughout the world, it also increased the possibility of spreading disease.

Scientist prepare the yellow fever vaccine | Library of Congress

Path to a Vaccine
After he became surgeon general of the Army in 1914, Gorgas met with Dr. Wickliffe Rose of the Rockefeller Foundation, which subsequently focused on eradicating yellow fever from the world. Rockefeller researchers traveled to yellow fever hotspots such as South America and Africa. Several of them died from the disease. One researcher, Dr. Alexander Mahaffy, discovered in 1927 that yellow fever could be transmitted and studied in animals. A Harvard scientist, Max Thieler, showed in 1930 that mice were susceptible to the yellow fever virus. Using mouse and chick embryos, Thieler later developed the most effective vaccine against yellow fever, called 17D, which immunized U.S. soldiers during World War II and became the world standard. The achievement won him the Nobel Prize in Medicine in 1951.

Outbreaks Continue
For the last 50 years, yellow fever has centered around South America and Africa, the only two places where it occurs today. Jungle yellow fever struck Central America in the 1950s and 1960s, and South America has experienced scattered outbreaks since then. Africa has seen the worst outbreaks, including epidemics in Central and East Africa between 1958 and 1966 that killed thousands of people. Hundreds died in a Ghanaian epidemic in the 1970s while Nigeria suffered thousands of fatalities from the disease in the 1980s. Other cases occurred in the 1990s, and in 2003, the World Health Organization cited new cases in West Africa and southern Sudan which caused at least 60 deaths. Immunization efforts in some French-speaking African countries between 1933 and 1961 resulted in the gradual disappearance of the disease there.

Freezing yellow fever vaccine before desiccation | Library of Congress

Current Status
Between 1996 and 2002, five people from the United States and Europe who traveled to South America or Africa contracted yellow fever and died. They were all unvaccinated. The Center for Disease Control and Prevention estimates that several hundred cases of yellow fever still occur each year, though because of underreporting the number could be much higher. Large populations remain unvaccinated and some health officials fear more instances of the disease. Vaccination, which is generally safe, and avoiding mosquito bites are the best preventive measures against yellow fever.

To date, there is no treatment or cure for yellow fever.

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Yellow Fever in the 20th Century and Today | American Experience | PBS

# data[].attributes.attachment_link.description
The Great Fever | Article In the 20th century, a vaccine for yellow fever was developed to protect people in regions where the disease still flourishes. Epidemics continued, however, during every decade of the century, and cases still surface to the present time.

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The new republic was only four years old, its capital recently established in Philadelphia, when the country suffered its first catastrophic epidemic. Yellow fever broke out in August 1793 and ravaged the city for three months, only subsiding in November. Twenty thousand people fled the city, as many as 5,000 died (ten percent of Philadelphia's population), and countless thousands of others suffered illness and hardship. No one then knew what caused the disease (a mosquito-borne virus), there was no effective treatment, and the epidemic only ended with the coming of cold weather that suppressed the mosquitoes.

There was acute need for volunteers to nurse the sick, help the bereft, and bury the dead. The Black community, under the leadership of Absalom Jones and Richard Allen, answered the call. A former slave who had worked to purchase his wife's freedom and then was manumitted himself at age thirty-eight, Jones was an Episcopalian minister and leader in the Black community. Fourteen years younger than Jones, and like him a former slave who had purchased his own freedom, Richard Allen was a Methodist who would become the founder of the AME Church. Together, Jones and Allen were co-leaders of the Free African Society, a mutual aid society of free Blacks, through which they organized the many volunteers who stepped forward to help.

In November, shortly after the contagion died down, people came back, and life began to return to normal, the publisher Matthew Carey (who had himself fled the town) printed a pamphlet called A Short Account of the Malignant Fever, Lately Prevalent in Philadelphia in which he recounted the horrors of the epidemic but also impugned members of the Black community for somehow spreading the disease, charging extortionate fees for their work, and stealing from the dead. Indignant at these racist aspersions and sensitive to the need to defend the image of their community, Absalom Jones and Richard Allen fought back.

The result, in early 1794, was the pamphlet from which the excerpts below are reprinted: A Narrative of the Proceedings of the Black People, During the Late Awful Calamity in Philadelphia. In it, Jones and Allen meticulously refuted Carey's charges with eyewitness testimony and hard evidence, while also chronicling the many acts of mercy and generosity performed by individuals-most of them named in full-from the Black community. The reputation of their people was vindicated, and it is no coincidence that when each of these Black ministers founded his own independent church later in 1794, there was extensive support from the White community. Absalom Jones and Richard Allen would continue their spiritual, political, and civic leadership well into the 1800s (Jones lived until 1816, Allen to 1831), and enter history as two of the heroic figures of the founding era.

Excerpts

from A Narrative of the Proceedings of the Black People, During the Late Awful Calamity in Philadelphia, 1794[1]

In consequence of a partial representation of the conduct of the people who were employed to nurse the sick, in the late calamitous state of the city of Philadelphia, we are solicited, by a number of those who feel themselves injured thereby, and by the advice of several respectable citizens, to step forward and declare facts as they really were; seeing that from our situation, on account of the charge we took upon us, we had it more fully and generally in our power, to know and observe the conduct and behaviour of those that were so employed.

Early in September, a solicitation appeared in the public papers, to the people of colour to come forward and assist the distressed, perishing, and neglected sick; with a kind of assurance, that people of our colour were not liable to take the infection. Upon which we and a few others met and consulted how to act on so truly alarming and melancholy an occasion. After some conversation, we found a freedom to go forth, confiding in him who can preserve in the midst of a burning fiery furnace, sensible that it was our duty to do all the good we could to our suffering fellow mortals. We set out to see where we could be useful. The first we visited was a man in Emsley's Alley, who was dying, and his wife lay dead at the time in the house, there were none to assist but two poor helpless children. We administered what relief we could, and applied to the overseers of the poor to have the woman buried. We visited upwards of twenty families that day-they were scenes of woe indeed! The Lord was pleased to strengthen us, and remove all fear from us, and disposed our hearts to be as useful as possible. . . .

Mr. Carey tells us, Bush-hill exhibited as wretched a picture of human misery, as ever existed. A profligate abandoned set of nurses and attendants (hardly any of good character could at that time be procured,) rioted on the provisions and comforts, prepared for the sick, who (unless at the hours when the doctors attended) were left almost entirely destitute of every assistance. The dying and dead were indiscriminately mingled together. The ordure and other evacuations of the sick, were allowed to remain in the most offensive state imaginable. Not the smallest appearance of order or regularity existed. It was in fact a great human slaughter-house, where numerous victims were immolated at the altar of intemperance.

It is unpleasant to point out the bad and unfeeling conduct of any colour, yet the defence we have undertaken obliges us to remark, that although "hardly any of good character at that time could be procured," yet only two black women were at this time in the hospital, and they were retained and the others discharged, when it was reduced to order and good government.

The bad consequences many of our colour apprehend from a partial relation of our conduct are, that it will prejudice the minds of the people in general against us-because it is impossible that one individual, can have knowledge of all, therefore at some future day, when some of the most virtuous, that were upon most praise-worthy motives, induced to serve the sick, may fall into the service of a family that are strangers to him, or her, and it is discovered that it is one of those stigmatised wretches, what may we suppose will be the consequence? Is it not reasonable to think the person will be abhorred, despised, and perhaps dismissed from employment, to their great disadvantage, would not this be hard? and have we not therefore sufficient reason to seek for redress? We can with certainty assure the public that we have seen more humanity, more real sensibility from the poor blacks, than from the poor whites. When many of the former, of their own accord rendered services where extreme necessity called for it, the general part of the poor white people were so dismayed, that instead of attempting to be useful, they in a manner hid themselves-a remarkable instance of this-A poor afflicted dying man, stood at his chamber window, praying and beseeching every one that passed by, to help him to a drink of water; a number of white people passed, and instead of being moved by the poor man's distress, they hurried as fast as they could out of the sound of his cries-until at length a gentleman, who seemed to be a foreigner came up, he could not pass by, but had not resolution enough to go into the house, he held eight dollars in his hand, and offered it to several as a reward for giving the poor man a drink of water, but was refused by every one, until a poor black man came up, the gentleman offered the eight dollars to him, if he would relieve the poor man with a little water, "Master" replied the good natured fellow, "I will supply the gentleman with water, but surely I will not take your money for it" nor could he be prevailed upon to accept his bounty: he went in, supplied the poor object with water, and rendered him every service he could.

A poor black man, named Sampson, went constantly from house to house where distress was, and gave assistance without fee or reward; he was smote with the disorder and died, after his death his family were neglected by those he had served.

Sarah Bass, a poor black widow, gave all the assistance she could, in several families, for which she did not receive any thing; and when any thing was offered her, she left it to the option of those she served.

A woman of our colour nursed Richard Mason and son, when they died, Richard's widow considering the risk the poor woman had run, and from observing the fears that sometimes rested on her mind, expected she would have demanded some thing considerable, but upon asking what she demanded, her reply was half a dollar per day. Mrs. Mason, intimated it was not sufficient for her attendance, she replied it was enough for what she had done, and would take no more. Mrs. Mason's feelings were such, that she settled an annuity of six pounds a year, on her, for life. Her name is Mary Scott.

An elderly black woman nursed __________ with great diligence and attention; when recovered he asked what he must give for her services-she replied "a dinner master on a cold winter's day," and thus she went from place to place rendering every service in her power without an eye to reward.

A young black woman, was requested to attend one night upon a white man and his wife, who were very ill, no other person could be had;-great wages were offered her-she replied, I will not go for money, if I go for money God will see it, and may be make me take the disorder and die, but if I go, and take no money, he may spare my life. She went about nine o'clock, and found them both on the floor; she could procure no candle or other light, but staid with them about two hours, and then left them. They both died that night. She was afterward very ill with the fever-her life was spared.

Cæsar Cranchal, a black man, offered his services to attend the sick, and said, I will not take your money. I will not sell my life for money. It is said he died with the flux.

A black lad, at the Widow Gilpin's, was intrusted with his young Master's keys, on his leaving the city, and transacted his business, with the greatest honesty, and dispatch, having unloaded a vessel for him in the time, and loaded it again.

A woman, that nursed David Bacon, charged with exemplary moderation, and said she would not have any more.

It may be said, in vindication of the conduct of those, who discovered ignorance or incapacity in nursing, that it is, in itself, a considerable art, derived from experience, as well as the exercise of the finer feelings of humanity-this experience, nine tenths of those employed, it is probable were wholly strangers to.

We do not recollect such acts of humanity from the poor white people, in all the round we have been engaged in. We could mention many other instances of the like nature, but think it needless.

It is unpleasant for us to make these remarks, but justice to our colour demands it.

[1] This text will be reprinted in the anthology Black Writers of the Founding Era, 1760−1800, ed. James G. Basker (Library of America, forthcoming).

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black volunteers in the nation’s first epidemic

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1793 | the new republic was only four years old

# data[].attributes.attachment_link.keywords[]
its capital recently established in philadelphia

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when the country suffered its first catastrophic epidemic. yellow fever broke out in august 1793 and ravaged the city for three months

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only subsiding in november. | the new republic was only four years old

# data[].attributes.attachment_link.keywords[]
its capital recently established in philadelphia

# data[].attributes.attachment_link.keywords[]
when the country suffered its first catastrophic epidemic. yellow fever broke out in august 1793 and ravaged the city for three months

# data[].attributes.attachment_link.keywords[]
only subsiding in november. twenty thousand people fled the city

# data[].attributes.attachment_link.keywords[]
000 died (ten percent of philadelphia’s population)

# data[].attributes.attachment_link.keywords[]
and countless thousands of others suffered illness and hardship. no one then knew what caused the disease (a mosquito-borne virus)

# data[].attributes.attachment_link.keywords[]
and the epidemic only ended with the coming of cold weather that suppressed the mosquitoes. there was acute need for volunteers to nurse the sick

# data[].attributes.attachment_link.keywords[]
under the leadership of absalom jones and richard allen

# data[].attributes.attachment_link.keywords[]
answered the call. a former slave who had worked to purchase his wife’s freedom and then was manumitted himself at age thirty-eight

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jones was an episcopalian minister and leader in the black community. fourteen years younger than jones

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and like him a former slave who had purchased his own freedom

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richard allen was a methodist who would become the founder of the ame church. together

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jones and allen were co-leaders of the free african society

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through which they organized the many volunteers who stepped forward to help. in november

# data[].attributes.attachment_link.keywords[]
the publisher matthew carey (who had himself fled the town) printed a pamphlet called a short account of the malignant fever

# data[].attributes.attachment_link.keywords[]
lately prevalent in philadelphia in which he recounted the horrors of the epidemic but also impugned members of the black community for somehow spreading the disease

# data[].attributes.attachment_link.keywords[]
charging extortionate fees for their work

# data[].attributes.attachment_link.keywords[]
and stealing from the dead. indignant at these racist aspersions and sensitive to the need to defend the image of their community

# data[].attributes.attachment_link.keywords[]
absalom jones and richard allen fought back. the result

# data[].attributes.attachment_link.keywords[]
was the pamphlet from which the excerpts below are reprinted: a narrative of the proceedings of the black people

# data[].attributes.attachment_link.keywords[]
during the late awful calamity in philadelphia. in it

# data[].attributes.attachment_link.keywords[]
jones and allen meticulously refuted carey’s charges with eyewitness testimony and hard evidence

# data[].attributes.attachment_link.keywords[]
while also chronicling the many acts of mercy and generosity performed by individuals—most of them named in full—from the black community. the reputation of their people was vindicated

# data[].attributes.attachment_link.keywords[]
and it is no coincidence that when each of these black ministers founded his own independent church later in 1794

# data[].attributes.attachment_link.keywords[]
there was extensive support from the white community. absalom jones and richard allen would continue their spiritual

# data[].attributes.attachment_link.keywords[]
and civic leadership well into the 1800s (jones lived until 1816

# data[].attributes.attachment_link.keywords[]
and enter history as two of the heroic figures of the founding era. excerpts from a narrative of the proceedings of the black people

# data[].attributes.attachment_link.keywords[]
during the late awful calamity in philadelphia

# data[].attributes.attachment_link.keywords[]
1794[1] in consequence of a partial representation of the conduct of the people who were employed to nurse the sick

# data[].attributes.attachment_link.keywords[]
in the late calamitous state of the city of philadelphia

# data[].attributes.attachment_link.keywords[]
by a number of those who feel themselves injured thereby

# data[].attributes.attachment_link.keywords[]
and by the advice of several respectable citizens

# data[].attributes.attachment_link.keywords[]
to step forward and declare facts as they really were; seeing that from our situation

# data[].attributes.attachment_link.keywords[]
on account of the charge we took upon us

# data[].attributes.attachment_link.keywords[]
we had it more fully and generally in our power

# data[].attributes.attachment_link.keywords[]
to know and observe the conduct and behaviour of those that were so employed. early in september

# data[].attributes.attachment_link.keywords[]
a solicitation appeared in the public papers

# data[].attributes.attachment_link.keywords[]
to the people of colour to come forward and assist the distressed

# data[].attributes.attachment_link.keywords[]
and neglected sick; with a kind of assurance

# data[].attributes.attachment_link.keywords[]
that people of our colour were not liable to take the infection. upon which we and a few others met and consulted how to act on so truly alarming and melancholy an occasion. after some conversation

# data[].attributes.attachment_link.keywords[]
confiding in him who can preserve in the midst of a burning fiery furnace

# data[].attributes.attachment_link.keywords[]
sensible that it was our duty to do all the good we could to our suffering fellow mortals. we set out to see where we could be useful. the first we visited was a man in emsley’s alley

# data[].attributes.attachment_link.keywords[]
and his wife lay dead at the time in the house

# data[].attributes.attachment_link.keywords[]
there were none to assist but two poor helpless children. we administered what relief we could

# data[].attributes.attachment_link.keywords[]
and applied to the overseers of the poor to have the woman buried. we visited upwards of twenty families that day—they were scenes of woe indeed! the lord was pleased to strengthen us

# data[].attributes.attachment_link.keywords[]
and disposed our hearts to be as useful as possible. . . . mr. carey tells us

# data[].attributes.attachment_link.keywords[]
bush-hill exhibited as wretched a picture of human misery

# data[].attributes.attachment_link.keywords[]
as ever existed. a profligate abandoned set of nurses and attendants (hardly any of good character could at that time be procured

# data[].attributes.attachment_link.keywords[]
who (unless at the hours when the doctors attended) were left almost entirely destitute of every assistance. the dying and dead were indiscriminately mingled together. the ordure and other evacuations of the sick

# data[].attributes.attachment_link.keywords[]
were allowed to remain in the most offensive state imaginable. not the smallest appearance of order or regularity existed. it was in fact a great human slaughter-house

# data[].attributes.attachment_link.keywords[]
where numerous victims were immolated at the altar of intemperance. it is unpleasant to point out the bad and unfeeling conduct of any colour

# data[].attributes.attachment_link.keywords[]
yet the defence we have undertaken obliges us to remark

# data[].attributes.attachment_link.keywords[]
that although “hardly any of good character at that time could be procured

# data[].attributes.attachment_link.keywords[]
” yet only two black women were at this time in the hospital

# data[].attributes.attachment_link.keywords[]
and they were retained and the others discharged

# data[].attributes.attachment_link.keywords[]
when it was reduced to order and good government. the bad consequences many of our colour apprehend from a partial relation of our conduct are

# data[].attributes.attachment_link.keywords[]
that it will prejudice the minds of the people in general against us—because it is impossible that one individual

# data[].attributes.attachment_link.keywords[]
that were upon most praise-worthy motives

# data[].attributes.attachment_link.keywords[]
may fall into the service of a family that are strangers to him

# data[].attributes.attachment_link.keywords[]
and it is discovered that it is one of those stigmatised wretches

# data[].attributes.attachment_link.keywords[]
what may we suppose will be the consequence? is it not reasonable to think the person will be abhorred

# data[].attributes.attachment_link.keywords[]
would not this be hard? and have we not therefore sufficient reason to seek for redress? we can with certainty assure the public that we have seen more humanity

# data[].attributes.attachment_link.keywords[]
more real sensibility from the poor blacks

# data[].attributes.attachment_link.keywords[]
than from the poor whites. when many of the former

# data[].attributes.attachment_link.keywords[]
of their own accord rendered services where extreme necessity called for it

# data[].attributes.attachment_link.keywords[]
the general part of the poor white people were so dismayed

# data[].attributes.attachment_link.keywords[]
they in a manner hid themselves—a remarkable instance of this—a poor afflicted dying man

# data[].attributes.attachment_link.keywords[]
praying and beseeching every one that passed by

# data[].attributes.attachment_link.keywords[]
to help him to a drink of water; a number of white people passed

# data[].attributes.attachment_link.keywords[]
and instead of being moved by the poor man’s distress

# data[].attributes.attachment_link.keywords[]
they hurried as fast as they could out of the sound of his cries—until at length a gentleman

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but had not resolution enough to go into the house

# data[].attributes.attachment_link.keywords[]
and offered it to several as a reward for giving the poor man a drink of water

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the gentleman offered the eight dollars to him

# data[].attributes.attachment_link.keywords[]
if he would relieve the poor man with a little water

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“master” replied the good natured fellow

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but surely i will not take your money for it” nor could he be prevailed upon to accept his bounty: he went in

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and rendered him every service he could. a poor black man

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went constantly from house to house where distress was

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and gave assistance without fee or reward; he was smote with the disorder and died

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after his death his family were neglected by those he had served. sarah bass

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for which she did not receive any thing; and when any thing was offered her

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she left it to the option of those she served. a woman of our colour nursed richard mason and son

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richard’s widow considering the risk the poor woman had run

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and from observing the fears that sometimes rested on her mind

# data[].attributes.attachment_link.keywords[]
expected she would have demanded some thing considerable

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her reply was half a dollar per day. mrs. mason

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intimated it was not sufficient for her attendance

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she replied it was enough for what she had done

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and would take no more. mrs. mason’s feelings were such

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that she settled an annuity of six pounds a year

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for life. her name is mary scott. an elderly black woman nursed __________ with great diligence and attention; when recovered he asked what he must give for her services—she replied “a dinner master on a cold winter’s day

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” and thus she went from place to place rendering every service in her power without an eye to reward. a young black woman

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was requested to attend one night upon a white man and his wife

# data[].attributes.attachment_link.keywords[]
no other person could be had;—great wages were offered her—she replied

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and may be make me take the disorder and die

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he may spare my life. she went about nine o’clock

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and found them both on the floor; she could procure no candle or other light

# data[].attributes.attachment_link.keywords[]
and then left them. they both died that night. she was afterward very ill with the fever—her life was spared. cæsar cranchal

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i will not take your money. i will not sell my life for money. it is said he died with the flux. a black lad

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was intrusted with his young master’s keys

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having unloaded a vessel for him in the time

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and said she would not have any more. it may be said

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who discovered ignorance or incapacity in nursing

# data[].attributes.attachment_link.keywords[]
as well as the exercise of the finer feelings of humanity—this experience

# data[].attributes.attachment_link.keywords[]
it is probable were wholly strangers to. we do not recollect such acts of humanity from the poor white people

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in all the round we have been engaged in. we could mention many other instances of the like nature

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but think it needless. it is unpleasant for us to make these remarks

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but justice to our colour demands it. [1] this text will be reprinted in the anthology black writers of the founding era

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Black Volunteers in the Nation's First Epidemic, 1793

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Black Volunteers in the Nation's First Epidemic, 1793 | The new republic was only four years old, its capital recently established in Philadelphia, when the country suffered its first catastrophic epidemic. Yellow fever broke out in August 1793 and ravaged the city for three months, only subsiding in November.

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Free African Society - Encyclopedia of Greater Philadelphia

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Headed by Black founding fathers Richard Allen (1760-1831) and Absalom Jones (1746-1818), the Free African Society was founded on April 12, 1787, as a nondenominational mutual aid society and the first dedicated to serving Philadelphia's burgeoning free Black community. Members contributed one shilling per month to fund programs to support their social and economic needs.

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In 1793, Philadelphia was struck with the worst outbreak of Yellow Fever ever recorded in North America. The fever took a devastating toll on the city as nearly 5,000 individuals died, among them close to 400 African Americans.

Above: Dead House on the Schuylkill during the yellow fever in Philadelphia in 1793, David Johnson Kennedy, Watercolor, Historical Society of Pennsylvania.

During the frenzy and fear of the epidemic, Dr. Benjamin Rush, signer of the Declaration of Independence and leading medical mind of the day, wrote to Richard Allen and Absalom Jones and implored them to step in and help the sick. Rush believed that African Americans were not as susceptible to the Yellow Fever.

Allen, Jones, and many other African Americans agreed to help the sick, working as everything from nurses to gravediggers. However, Benjamin Rush's theory was wrong, and in the end blacks died from Yellow Fever in similar percentages to whites. Allen was struck by the fever in late September and was lucky to survive when so many had perished.

By late November when the cold set in, the epidemic abated the city. Rather than being regaled as heroes, Allen, Jones, and the black community were vilified. Matthew Carey's pamphlet A Short Account of the Malignant Fever portrayed the African American community as money-hungry opportunists and praised Stephen Girard and other whites who arranged hospitals outside of the city as the true heroes of the crisis. Jones and Allen struck back with their own pamphlet to defend African Americans.

Right: A Narrative of the Proceedings of the Black People During the Late Awful Calamity in Philadelphia in the Year 1793; And a Refutation of Some Censures Thrown upon Them in Some Late Publications, Richard Allen & Absalom Jones (Philadelphia, 1794), The Library Company of Philadelphia.

# data[].attributes.attachment_link.description
In 1793, Philadelphia was struck with the worst outbreak of Yellow Fever ever recorded in North America. The fever took a devastating toll on the city as nearly 5,000 individuals died, among them close to 400 African Americans. Above: Dead House on the Schuylkill during the yellow fever in Philadelphia in 1793, David Johnson Kennedy, Watercolor, Historical Society of Pennsylvania.

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Yellow Fever, Causes, Signs and Symptoms, Diagnosis and Treatment.

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Yellow fever appeared in the U.S. in the late 17th century. The deadly virus continued to strike cities, mostly eastern seaports and Gulf Coast cities, for the next two hundred years, killing hundreds, sometimes thousands in a single summer.

1. Philadelphia; August-November 1793; approximately 5,000 dead
This outbreak killed about 10% of the city's population, and thousands more fled, including an infected Alexander Hamilton and his wife. Dr. Benjamin Rush, who stayed, issued guidelines for avoiding infection and helped set up a "fever hospital" for victims.

2. New York City; July-October 1795; 730 dead
New York City, which in 1793 had turned away refugees from the epidemic in Philadelphia, suffered its own epidemic two summers later.

3. Boston, New York City and Philadelphia; Summer 1798; more than 5,000 dead
Concurrent epidemics hit the nation's three major cities.

4. Baltimore; Summer 1800; 1,200 dead
As the 19th century wore on, yellow fever outbreaks would increasingly be confined to the southern United States.

5. New Orleans; Summer 1853; 8000 or more dead
This outbreak illustrated a racial disparity in yellow fever mortality; 7.4% of white residents died, but only 0.2% of blacks.

6. Norfolk; June-Oct 1855; 2,000 dead
This epidemic, like many others in America, began with the arrival of a disease-carrying ship from the West Indies.

7. Mississippi Valley; May-Oct 1878; 20,000 dead
Starting in New Orleans, this epidemic spread up the Mississippi Valley to Memphis. More than half of the 47,000 residents of Memphis fled the city; more than 5,000 died that summer of yellow fever.

8. Cuba; Summer 1898; hundreds dead
Disease killed more than five times as many American soldiers as enemy bullets during the Spanish-American war; yellow fever was among the culprits, and its impact led to the establishment of a U.S. Army Yellow Fever Board led by Walter Reed that would unravel the mystery of yellow fever transmission and lead to its eradication in America.

9. New Orleans; May-October 1905; more than 900 dead
Yellow fever epidemics took more than 41,000 lives in New Orleans from 1817-1905, but the 1905 outbreak was America's last. Today, yellow fever continues to appear in small outbreaks in South America and more serious epidemics in West and Central Africa.

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Major American Epidemics of Yellow Fever (1793-1905) | American Experience | PBS

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Yellow fever appeared in the U.S. in the late 17th century. The deadly virus continued to strike cities, mostly eastern seaports and Gulf Coast cities, for the next two hundred years, killing hundreds, sometimes thousands in a single summer.

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For more than a century beginning in the late seventeenth century, sudden outbreaks of yellow fever sowed death and panic throughout Philadelphia and its environs. With medical science seemingly powerless against it, yellow fever was a terrifying and mysterious threat that rivaled any disease of the era in its capacity to take lives and disrupt society.

Yellow fever is a Flavivirus that spreads among humans via the bite of Aedes aegypti mosquitoes. Once introduced to a human host, the virus begins replicating in the lymph nodes. Initial symptoms include aches and pains, fever, nausea, and dizziness, lasting several days before receding. In serious cases, the symptoms return with renewed intensity as the disease spreads to the liver, inducing jaundice, delirium, and internal hemorrhaging. The victim begins bleeding from the ears and nose, retching up a blend of gastric contents and blood known as the "coffee grounds" or "black vomit." In the terminal phase, the victim falls comatose as his organs and circulatory system begin to fail, usually expiring as the liver or kidneys finally give out, some 7-10 days after the relapse. Those who survived the ordeal acquired immunity to the disease, but any population composed largely of unseasoned newcomers provided a fertile environment for an outbreak.

Epidemiological evidence suggests that both the virus and its vector originated in Africa. They crossed the Atlantic by the slave trade, becoming endemic in the sugar islands of the West Indies. Once established there, it was only a matter of time before the fever spread to North American ports. From its earliest days, Philadelphia carried on a bustling trade with the Caribbean, and a "Barbados Distemper" struck the city in 1699, felling 220.

For almost a century, yellow fever was an erratic visitor, abruptly appearing after long intervals of relative inactivity. Significant outbreaks appeared in 1741, 1747, and 1762, but major episodes were too uncommon and unpredictable to have a broader political impact until the 1790s, when the fever began striking with greater frequency and fury.

1793: Yellow Fever Returns

After some three decades absent, yellow fever returned to Philadelphia with a vengeance in 1793, during the period that it served as the capital of both Pennsylvania and the United States. Beginning from a cluster of infections near the Delaware waterfront, the fever spread rapidly through the summer and autumn, fueling panic throughout the city. Those who could fled the city to destinations in healthier countryside, like Germantown and Gray's Ferry, an exodus numbering in the thousands. Among those who remained, the fever claimed an estimated 5,000 lives. Other American cities embargoed the nation's capital, fearful that traffic from Philadelphia could introduce the infection.

Officers of federal, state and municipal government vacated the city, leaving management of the crisis to Mayor Matthew Clarkson and a committee of volunteers led by merchant Stephen Girard, who organized a fever hospital at the Bush-Hill mansion built by Andrew Hamilton. Black Philadelphians served in disproportionate numbers, owing to a widely held belief that they were immune to the fever, and their heroic service as nurses, porters, and inspectors is widely regarded as a formative event in the history of Black Philadelphia. When printer Mathew Carey published an account of the crisis impugning the conduct of African-American volunteers, Black church leaders Absalom Jones and Richard Allen responded by publishing a powerful rebuttal of the charges, forcing Carey to amend later editions of his tract.

The epidemic also set off a wide-ranging debate over the cause of the fever and the best means of controlling it. Philadelphia's College of Physicians contended that it was both contagious in nature and foreign in origin, while a faction led by Benjamin Rush, the city's most celebrated doctor, argued that only domestic environmental factors were to blame. Incorporating insights from both parties, Pennsylvania established a new Philadelphia Board of Health in 1795 to enforce both quarantine and sanitary regulations.

1793: The Model Response

Notwithstanding the new measures, the fever returned seven times in the following twelve years, and 1793 set the model for how Philadelphians responded to subsequent outbreaks. Each episode spurred similar patterns of evacuation, isolation, and scapegoating, and stoked the ongoing controversy within the medical community and motivated broader, though futile, efforts to ameliorate the effects of the disease. Nursing may have offered some comfort, but only winter frost-and its extermination of the mosquitoes-brought an end to each fever year.

The ordeal of fever had a profound effect on the city and the country. It was one of several factors in Philadelphia's decline relative to rising ports like New York City. It inspired literary and journalistic development as writers and printers discussed, described, and debated the disease. The urban nature of the fever fueled the agrarian romanticism of the Jeffersonian era. And throughout the country, and the broader Atlantic World, medical men struggled to understand a foe that thwarted their best efforts.

Yellow fever struck Philadelphia and other northern ports only sporadically after 1820, but it remained a persistent problem in the American South until the turn of the century, when researchers like Carlos Finlay and Walter Reed unraveled the etiology of the disease and formulated effective measures to control it.

Simon Finger holds a Ph.D. from Princeton University and is the author of The Contagious City: The Politics of Public Health in Early Philadelphia (Ithaca, N.Y.: Cornell University Press, 2012). (Author information current at time of publication.)

Essay Copyright 2011, University of Pennsylvania Press.

Estes, J. Worth, and Smith, Billy G. A Melancholy Scene of Devastation: The Public Response to the 1793 Yellow Fever Epidemic. Philadelphia: Science History Publications/USA, 1997.

Finger, Simon. The Contagious City: The Politics of Public Health in Early Philadelphia Ithaca: Cornell University Press, forthcoming 2012.

McNeill, J.R., Mosquito Empires: Ecology and War in the Greater Caribbean, 1620-1914, New York: Cambridge University Press, 2010.

Miller, Jacqueline. "The Body Politic: Passions, Pestilence, and Political Culture," Ph.D. Diss., Rutgers University, 1995.

Powell, J.H. Bring out Your Dead: The Great Plague of Yellow Fever in Philadelphia in 1793. Philadelphia: University of Pennsylvania Press, 1949.

Taylor, Sean, "'We Live in the Midst of Death': Yellow Fever, Moral Economy, and Public Health in Philadelphia, 1793-1805." Ph.D. Diss., Northern Illinois University, 2001.

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Yellow Fever - Encyclopedia of Greater Philadelphia

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For more than a century beginning in the late seventeenth century, sudden outbreaks of yellow fever sowed death and panic throughout Philadelphia and its environs. With medical science seemingly powerless against it, yellow fever was a terrifying and mysterious threat that rivaled any disease of the era in its capacity to take lives and disrupt society.

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The emergence of yellow fever in the United States brought death and panic, but also initiated a cascade of research and discovery. The tireless work of scientists initiated theories of how the disease was spread, from miasmas to virus-harboring vectors, and led to the development of vaccines and diagnostic technology that are still commonly used today.

It was 1793 in Philadelphia and the summer was proving to be one of the hottest on record. A blanket of humidity covered the city, fed by putrid swamps that served as breeding grounds for the Aedes aegypti mosquito. While smaller outbreaks of yellow fever had occurred in the U.S. since 1693, this year would prove to be different. The capital city would be decimated. In just a matter of months, 10% of Philadelphia's population was dead and a greater proportion had fled the city in fear for their lives.

The Aedes aegypti mosquito taking a blood meal.

Yellow fever is caused by a virus in the family Flaviviridae, and it is transmitted by the Aedes aegypti mosquito. The yellow fever virus most likely originated in Africa and arrived in the Western Hemisphere in the 1600s as a result of slave trade. The mosquito vector was likely introduced to the U.S. via water barrels on trade ships arriving from countries with endemic yellow fever. The virus followed when slaves from areas with endemic disease arrived. The hungry mosquitos then spread the virus from infected to uninfected in the New World. While many who are infected do not experience any symptoms or have mild symptoms, others have fever, muscle pain, headache, nausea and vomiting. A small percentage of people infected with the virus develop a life-threatening form of the disease that involves high fevers, internal bleeding, vomiting of blood and jaundice-which is where the "yellow" in yellow fever comes from. It has been estimated that for every 1 case of severe infection, there are between 1 and 70 infections that are asymptomatic or mild.

By the time shiploads of refugees from the French colony of St. Domingue arrived at the ports of Philadelphia, it was primed for a mosquito-driven epidemic. The city was surrounded by marshes and swamps, and human and animal waste was tossed into holes in the ground that captured and held rain runoff. While individuals who came to Philadelphia from areas where yellow fever was endemic had some level of immunity, most of the population was immunologically naive to the virus and therefore susceptible to its devastation.

1892 etching titled "Death of Aurelio Caballero due to yellow fever in Veracruz," by Jose Guadalupe Posada.

Early Diagnostics

The discovery of the causative agent of yellow fever was a decades-long process. While Cuban physician Carlos Finlay first described the Aedes aegypti mosquito as the carrier of the disease in 1886, he was ridiculed for this theory. Finlay's discovery was accepted 20 years later only after U.S. Army scientists working with Dr. Walter Reed confirmed that this was in fact correct. The work of Reed's team also confirmed that yellow fever was caused by an agent small enough to pass through bacteria filters, but it was more than 25 years before the virus was first isolated.

In 1930, a Harvard virologist named Max Theiler discovered that white mice were susceptible to intracerebral inoculation with the yellow fever virus. This discovery led to the idea that mice could be used to test for the presence of protective antibodies. Researchers added mouse brain infected with yellow fever virus cocktail to sera with antibodies against the yellow fever virus and subsequently injected this mixture into the brains of other mice. The level of protection against yellow fever disease was measured by the number of mice that lived or died during a specific incubation period following injection.

Drs. Sawyer, Lloyd and Theiler elaborated on this work by developing a method for determining the protective effects of sera against yellow fever called the intraperitoneal protection test in mice. Once optimized, this test allowed for the quantitation of protective antibodies in humans and became a critical tool in studying the epidemiology of the disease, as well as evaluating the performance of vaccines. Technology for detecting antibodies to yellow fever virus evolved over the years, and by 1960 hemagglutination-inhibition and complement fixation tests were available, which simplified the detection of antibodies to yellow fever.

Modern Diagnostics for Yellow Fever

The last major outbreak of yellow fever in the U.S. occurred in 1905 in New Orleans. Today, yellow fever is endemic in tropical and subtropical regions of South America and Africa. While the development of a yellow fever vaccine (Theiler won a Nobel prize for this work) has saved countless lives over the years, the global burden of this disease is still high. Urban transmission of the yellow fever virus can be controlled by public health interventions, but the enzootic/sylvatic cycle (where the disease is spread between mosquitoes and non-human primates) is much harder to control. This second cycle of transmission leads to large outbreaks due to spillover from non-human primate populations. Most recently, outbreaks of yellow fever have been reported in several states in Nigeria and Brazil. The true incidence is unknown due to limited diagnostic availability and ground surveillance in endemic areas, but is estimated to be between 200,000-300,000 cases per year.

Urban, intermediate/savannah and jungle/sylvatic cycles of yellow fever virus transmission.

Yellow fever can be difficult to diagnose because it mimics other severe diseases like malaria, leptospirosis and other hemorrhagic fevers. Today, the most commonly used yellow fever diagnostics include enzyme-linked immunosorbent assay (ELISA), which tests for antibodies, and reverse transcription-polymerase chain reaction (RT-PCR), which tests for viral genetic material. RT-PCR testing of the blood can detect the virus within the first few days of infection, but may be unreliable after that point when the patient may become symptomatic. Because of this, negative RT-PCR results cannot rule out infection. Antibody testing is a commonly used methodology, but comes with its own challenges. According to the World Health Organization's 2018 yellow fever report, there are no commercially available IgM kits for yellow fever available, pushing labs to validate in-house protocols using purified antigens. Additionally, cross-reactivity with other flaviviruses, such as dengue and Zika, is high in areas with co-circulation, and positive antibody results should be confirmed with a more specific test like plaque-reduction neutralization (PRNT). Finally, serologic testing can be complicated by vaccine-induced antibodies and test results from patients in areas with ongoing vaccine efforts should be interpreted with caution.

As is true with all diagnostic tests, clinical context is incredibly important for accurate interpretation of a yellow fever test result. In the U.S., a preliminary diagnosis is typically made based on presenting symptoms, vaccination status and travel history. All of these components must be taken into account when interpreting a yellow fever test result.

Modern Yellow Fever Research

Prevention of yellow fever primarily relies on vaccination, as there is no antiviral treatment available for the disease. While the live-attenuated vaccine has been demonstrated to be safe and effective (lifelong protection offered from one shot within 30 days of immunization in 99% of people who receive it), production can be slow and result in a low vaccine supply for areas in need. Since the sylvatic cycle of yellow fever is hard to control and can lead to large outbreaks, research that focuses on how yellow fever affects non-human primates in areas of South America and Africa, as well as the role of non-human primates in the spread of yellow fever is urgently needed.

New areas of research have begun to focus on intervention planning, which is vital to preventing large and deadly outbreaks. Some researchers are using available laboratory and epidemiology data to build models that assess vaccine impact, while others are developing methods to predict yellow fever epidemics. Climate change, particularly warming, has increased the spread of mosquitoes that can harbor the yellow fever virus to areas outside of where the disease is currently endemic. Additionally, large spillover outbreaks like the ones recently seen in Brazil and Nigeria demonstrate the potential for re-urbanization of the virus. Research that focuses on preventing large outbreaks is imperative to ensuring that yellow fever doesn't become the next pandemic.

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History of Yellow Fever in the U.S. | ASM.org

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There was a time when yellow fever ravaged the United States. These outbreaks led to groundbreaking research that led to current diagnostic tools, but more work is needed to control future outbreaks of this deadly disease.

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This is an update on the yellow fever situation in the WHO African Region since the last disease outbreak news was published on 2 September 2022. From 1 January 2021 to 7 December 2022, a total of 203 confirmed and 252 probable cases with 40 deaths (Case Fatality Ratio 9%) were reported to WHO from 13 countries in the WHO African Region. Risk factors for further yellow fever spread and amplification include low population immunity, population movements, viral transmission dynamics, and climate and environmental factors that have contributed to the spread of Aedes mosquitoes. Recent Reactive Vaccination Campaigns increase population immunity and may have contributed to reducing the risk of yellow fever spread in targeted countries, resulting in a gradual downward trend in reported confirmed cases in 2022. However, the countries remain at high risk.

In 2022, 12 countries in the WHO African Region have reported confirmed cases of yellow fever (Cameroon, the Central African Republic, Chad, Côte d'Ivoire, the Democratic Republic of the Congo, Ghana, Kenya, Niger, Nigeria, the Republic of the Congo, Sierra Leone and Uganda). Eight of these countries are experiencing a continuation of transmission from 2021 (Cameroon, the Central African Republic, Chad, Côte d'Ivoire, the Democratic Republic of the Congo, Ghana, Nigeria, and the Republic of the Congo) and four countries are newly reporting confirmed cases (Kenya, Niger, Sierra Leone and Uganda). One country, Gabon, reported an isolated confirmed case in 2021, but no further cases were registered in 2022.

Since 2021, a total of 203 confirmed and 252 probable cases with 40 deaths and a CFR of 9% have been reported. Of these, 23 deaths have been reported among confirmed cases (CFR among confirmed cases 11%) (Table 1). The high overall CFR among confirmed cases in 2021 (17 deaths, 11%) continued in 2022 (six deaths, 12%).

The male-to-female ratio among confirmed cases is not significantly different in 2021 and 2022 (1.3 and 1.6 respectively). The most affected age group amongst confirmed cases in 2021 was 10 years and below; meanwhile, the most affected group in 2022 is 20 to 30 years old. Overall, about 71% of confirmed cases are aged 30 years and below, and children aged 10 years and below are disproportionately affected.

According to the WHO/UNICEF Estimates of National Immunization Coverage (WUENIC), in 2021 routine immunization coverage against yellow fever in the African Region for childhood vaccinations was 48%, much lower than the 80% threshold required to confer population immunity against yellow fever, indicating the presence of an underlying susceptible population at risk of yellow fever and the risk of continued transmission. Country-specific estimates of vaccination coverage for 2021 are 54% in Cameroon, 41% in the Central African Republic, 45% in Chad, 67% in the Republic of the Congo, 65% in Côte d'Ivoire, 56% in the Democratic Republic of the Congo, 64% in Gabon, 94% in Ghana, 7% in Kenya, 80% in Niger (subnational introduction limited to four counties in 2021), 63% in Nigeria and 85% in Sierra Leone. Uganda has recently rolled-out yellow fever into the Routine Immunization programme.

Increasing population immunity through past and ongoing Preventive Mass Vaccination Campaigns (PMVC) supported through the EYE Strategy, and Reactive Vaccination Campaigns (RVC) have increased population immunity rapidly in implementing countries which has contributed to reducing the risk of spread of yellow fever in targeted countries. This may contribute to the gradual downward trend in reported confirmed cases in 2022, but should be noted that there is also variation in virus transmission dynamics that are difficult to predict.
Figure 1. Number of probable and confirmed yellow fever cases by week of symptom onset in 13 reporting countries in the WHO African Region (1 January 2021 to 7 December 2022) Figure 2. Distribution of reported probable and confirmed yellow fever cases in 13 countries in the WHO African Region between 1 January 2021 and 7 December 2022 Table 1. Classification of reported probable and confirmed yellow fever cases and deaths by country in the WHO African Region, 1 January 2021 to 7 December 2022 Surveillance and Laboratory.

WHO provides support to national health authorities in conducting field investigations and determining the epidemiological classification of yellow fever cases. A total of 51 personnel from at least 10 countries have been trained to investigate confirmed or probable cases of yellow fever. Furthermore, case investigation reports were reviewed, and feedback was provided to field teams to assess disease exposure and risk of disease spread.

An innovative programme to facilitate the international shipment of yellow fever samples to regional reference laboratories, as well as laboratory testing and capacity building, has been initiated with support from the EYE Strategy. WHO is engaged in ongoing activities to support countries in the laboratory diagnosis of yellow fever, including periodic accreditation visits and capacity development.

Reactive vaccination

Since the beginning of the current outbreak (2021 to 7 December 2022), a total of 4 385 320 persons have been vaccinated in five countries: Cameroon, the Central African Republic, Chad, Ghana and Kenya, as part of the ICG-supported response. Nine ICG requests for vaccination campaigns were approved for Cameroon (one request), the Central African Republic (two requests), Chad (two requests), Ghana (two requests), Kenya (one request), and Niger (one request).

Reactive campaign conducted in Kembe Satema in the Central African Republicfrom 2 to 19 November 2022 had 101.7% coverage. Based on preliminary results, the campaign in Bambari, the Central African Republic, which ended on 23 November 2022, had 87.7% coverage.

Final results are pending from an ICG-supported RVC in Niger, which is anticipated to protect approximately 1.1 million people.

Preventive mass campaign vaccination

Most priority countries have conducted a PMVC against yellow fever or are in process. Gabon, Kenya, and Niger have not planned PMVCs, however, they are included in the EYE Strategy as priority countries. Approximately 50 million people are expected to be protected by PMVCs conducted in 2022.

Chad: The country has prepared an application for a PMVC to be submited in January 2023. Weekly risk analysis sessions supported by the EYE Strategy have been conducted since 18 October 2022 to inform the planning of priority areas for the PMVC.

The Republic of the Congo: PMVC for yellow fever and measles integrated vaccination was organized from 5 to 14 August 2022 in 11 out of 12 departments with a coverage of 93% for yellow fever (preliminary report). The final report of the campaign and the mandatory Post Campaign Coverage Survey (PCCS) are pending.

The Democratic Republic of the Congo: Eight provinces have organized preventive campaigns in 2021 including Bas-Uele, Equateur, Haut-Uele, Mongala, Nord-Ubangi, Sud-Ubangi, Tshopo and Tshuapa. Three provinces have been scheduled to conduct preventive campaigns from the end of November 2022 through January 2023, and include Maniema, Sankuru and Sud Kivu.

Nigeria: The country has entered its final phases of PMVCs. In 2022 alone, campaigns have been conducted in Adamawa, Borno (special approach), Enugu, Gombe, Kano and Ogun States. Bayelsa State is planned for early 2023. The country is anticipated to complete nation-wide PMVCs by 2024.

Uganda: The country introduced yellow fever vaccination into routine immunization in late October 2022. In addition, 10 of 13 million vaccine doses have been received for PMVC, the rest were expected at the end of November 2022 but have not yet been received. PMVC has been planned for late January 2023.

Prevention of International Spread and Points of Entry (PoE)

Yellow fever is an epidemic-prone, vaccine-preventable disease caused by an arbovirus transmitted to humans by the bites of infected Aedes and Haemagogus mosquitoes. The incubation period ranges from 3 to 6 days. Many people do not experience symptoms, but when they occur, the most common are fever, muscle pain with prominent back pain, headache, loss of appetite, and nausea or vomiting. In most cases, symptoms disappear after 3 to 4 days. A small percentage of cases progress to a toxic phase with systemic infection affecting the liver and kidneys. These individuals can have more severe symptoms of high-grade fever, abdominal pain with vomiting, jaundice and dark urine caused by acute liver and kidney failure. Bleeding can occur from the mouth, nose, eyes, or stomach. Death can occur within 7 - 10 days in about half of cases with severe symptoms.

Yellow fever is prevented by an effective vaccine, which is safe and affordable. A single dose of yellow fever vaccine is sufficient to grant sustained immunity and life-long protection against yellow fever disease. A booster dose of the vaccine is not needed. The vaccine provides effective immunity within 10 days for 80-100% of people vaccinated, and within 30 days for more than 99% of people vaccinated.

All 13 countries that reported confirmed cases have implemented requirements for proof of vaccination against yellow fever as a condition for entry. Ten countries require proof of vaccination against yellow fever for any traveller, regardless of the origin of their voyage; whereas three countries (Chad, Kenya, and Nigeria) require proof of vaccination against yellow fever for travellers arriving from countries with areas at risk for yellow fever transmission as determined by the WHO Secretariat.

Between 26 August 2022 and 29 November 2022, there have been 22 additional confirmed cases of yellow fever reported from ten countries. However, based on retrospective classification of the cases, there were only seven new confirmed cases and one death. Countries including Burkina Faso, Senegal and Togo have reported probable cases that were subsequently discarded, indicating that there is enhanced surveillance put in place. However, there is still persistent yellow fever virus circulation, as several of the recent confirmations have been from locations with little or no underlying immunity (e.g., near urban areas in Cameroon and Uganda; areas with no history of yellow fever vaccination such as Isiolo county, Kenya) hard-to-reach and under-served populations, including children that have been disproportionately impacted.

Based on the current situation of yellow fever in the WHO African region, the risk at the regional level was re-assessed as moderate on 12 December 2022 (high in November 2021 and June 2022) due to:

1. The decrease in the number of reported cases and the increasing population immunity, since there are ongoing and recent preventive vaccination campaigns, as well as reactive campaigns that have been organized in the affected countries, with more than four million people vaccinated in five countries (Ghana, Cameroon, Chad, the Central African Republic and Kenya), and an estimated 50 million people immunized during the PMVCs in 2021-2022 (Nigeria, the Democratic Republic of the Congo, the Republic of the Congo) supported by the EYE Strategy.

2. There is ongoing yellow fever virus circulation in some high-risk areas, the most recent cases, and outbreaks are reported in areas impacted by underlying risk factors, including gaps in routine immunization, missed special populations (e.g., nomadic or pastoralists and other mobile populations), security and access challenges.

3. Most confirmed cases were reported in the last quarter of 2021, however several of the recent confirmations have been from urban areas and/or locations with little or no underlying immunity (e.g., near urban areas in Cameroon and Uganda; areas with no history of yellow fever vaccination);

4. Case classifications, and response operations remain a challenge;

5. Delays in detection and investigation; delays in the implementation of previously planned PMVC, competing outbreaks and pandemics of COVID-19 and Mpox that are attracting more attention in yellow fever-affected countries, and security constraints in affected areas (the Central African Republic, far North of Cameroon, Eastern - the Democratic Republic of the Congo, and Northern Nigeria), population movement, all present risks that could lead to new yellow fever transmission.

The overall global risk remains low, as no cases related to this current outbreak have been reported at this stage outside of the African region. However, there are favorable ecosystems for yellow fever outside the African region, especially in the neigbouring countries in the WHO Eastern Mediterranean Region. There might be challenges in surveillance and immunization capacities due to the potential onward transmission through viremic travellers and due to the presence of the competent vector, if not detected in a timely way.

The impact on public health will persist until the ongoing outbreaks are controlled, vaccination coverage is high and immunity gaps in the population are closed. The importation of cases to countries with suboptimal coverage and persisting population immunity gaps poses a high risk and may jeopardize the tremendous efforts invested to achieve elimination.

Transmission can be amplified in circumstances where the Aedes mosquitos (day feeder) are present in urban settings and densely populated areas causing rapid spread of the disease.

Surveillance: WHO recommends close monitoring of the situation with active cross-border coordination and information sharing, due to the possibility of cases in neighboring countries. Enhanced surveillance with investigation and laboratory testing of suspect cases is recommended.

Vaccination: Vaccination is the primary means for the prevention and control of yellow fever. Yellow fever vaccines approved by WHO are safe, highly effective, and provide life-long protection against infection.

The countries reporting yellow fever cases and outbreaks are all high-priority countries for the EYE Strategy. The EYE Strategy recommends that all high-risk countries introduce yellow fever vaccination into their routine immunization (RI) schedule for those aged 9 months (Ethiopia, South Sudan have yet to introduce it into RI). Review of the risk analysis and scope of immunization activities to protect the population could help avert the risk of future outbreaks (e.g. Kenya).

To protect populations in high-risk areas in the longer term, it is important to continue the roll-out of Preventive Mass Vaccination Campaigns (PMVCs) and bolster Routine Immunization (RI), as well as take steps to strengthen the application of International Health Regulations (IHR 2005) and bolster surveillance for rapid detection aligned to EYE objectives.

WHO recommends vaccination for all international travellers, aged 9 months and older, going to areas determined by the WHO Secretariat as at risk for yellow fever transmission and for additional areas the recommendation for vaccination of international travellers is subject to the assessment of the likelihood of exposure of each individual traveller.

Yellow fever vaccination is safe, highly effective and a single dose provides life-long protection. Yellow fever vaccination is not recommended for infants younger than 9 months, except during epidemics when the risk of yellow fever virus transmission may be very high. The risks and benefits of vaccination in this age group should be carefully considered before vaccination. The vaccine should be used with caution during pregnancy or breastfeeding. However, pregnant or breastfeeding women may be vaccinated during epidemics or if travel to a country or area with a risk of transmission is unavoidable.

According to the provisions of the International Health Regulations (IHR), any country may decide to implement the requirement for proof of vaccination against yellow fever for arriving travellers. For international travel purposes, the proof of vaccination against yellow fever is only valid if recorded in the International Certificate of Vaccination or Prophylaxis. The International Certificate of Vaccination or Prophylaxis becomes valid 10 days after vaccination against yellow fever and extends for the life of the person vaccinated with a WHO-approved vaccine. A booster dose of the yellow fever vaccine cannot be required of international travellers as a condition of entry.

Vector control: In urban centres, targeted vector control measures are also helpful to interrupt transmission. As a general precaution, WHO recommends avoidance of mosquito bites, including the use of repellents and insecticide-treated mosquito nets. The highest risk for transmission of yellow fever virus is during the day and early evening.

Risk communication: WHO encourages its Member States to take all actions necessary to keep travellers well informed of risks and preventive measures including vaccination. Travellers should be made aware of yellow fever symptoms and signs and instructed to rapidly seek medical advice if presenting signs and symptoms suggestive of yellow fever infection. Infected returning travellers may pose a risk for the establishment of local cycles of yellow fever transmission in areas where a competent vector is present.

International travel and trade: WHO advises against the application of any travel or trade restrictions to the Region.

The updated areas at-risk for yellow fever transmission and the related recommendations for vaccination of international travellers were updated by WHO on 1 July 2020; the map of revised areas at risk and yellow fever vaccination recommendations is available on the WHO International Travel and Health website.

Citable reference: World Health Organization (3 January 2023). Disease Outbreak News; Yellow fever in East, West, and Central Africa.Available at: https://www.who.int/emergencies/disease-outbreak-news/item/2022-DON431

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Yellow fever- East, West and Central Africa region

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This is an update on the yellow fever situation in the WHO African Region since the last disease outbreak news was published on 2 September 2022. From 1 January 2021 to 7 December 2022, a total of 203 confirmed and 252 probable cases with 40 deaths (Case Fatality Ratio 9%) were reported to WHO from 13 countries in the WHO African Region.

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Fever (1793-1820) - Philadelphia: The Great Experiment