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Discovered in 1968 in Norwalk, Ohio where it was originally given the name ‘Norwalk virus’ for where it originated

The first strain of norovirus was identified by Albert Kapikian from the US National Institute of Health, after first outbreak spread at a school

Highly contagoius, as a result the virus is worldwide

Norovirus leads to gastroenteritis, inflammation of the intestines and stomach lining due to touching contaminated surfaces or injesting contaminated foods that have the virus on them

Exhibits similar symptoms to stomach flu (vomiting, diarrhea and nausea)

Resources:

https://pubmed.ncbi.nlm.nih.gov/30020637

https://www.science.org/content/article/why-ferrari-viruses-surging-through-northern-hemisphere

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Norovirus evolves through genetic recombination and point mutations

Genetic recombination allows for a wide range of diversity among population and point mutations can occur from only a single nucleotide base alteration

Norovirus phylogeny looks at the evolutionary relationship of different norovirus strains

Phylogeny can be broken down into genotypes and genogroups

There ten genogroups (GI-GX) which account for genetic variation

Genogroups GI and GII are the most prominent in the population

Over 40 genotypes have been classified, the most prominent is GII.4

Resources:

https://gutpathogens.biomedcentral.com/articles/10.1186/s13099-018-0263-8/figures/2

https://pmc.ncbi.nlm.nih.gov/articles/PMC6112129/

https://bmcgenomdata.biomedcentral.com/articles/10.1186/s12863-022-01066-6

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Norovirus is considered to have a non-enveloped cell structure, meaning it lacks a cell wall, cytoplasmic membrane and outer membrane surrounding it's genetic material

Norovirus has a genome that consists of only single stranded RNA, averaging 7.5kb (kilobases) in length and 30 nm (micrometers) in diameter

Norovirus's RNA is arranged in three different segments called open reading frames, which are genetic sequences signaling the end of the protein that needs to be translated has completed once the marker is reached (stop codon)

There are three open reading frames (ORF's) in Norovirus:

ORF1 is responsible for encoding the protein RNA polymerase, which is essential for the viral replication ability of the virus

ORF2 and ORF3 are responsible for encoding for the capsid proteins which give the virus the ability to attach to its host cell

Resources:

https://biologyinsights.com/norovirus-structure-transmission-immunity-and-detection/

https://en.wikipedia.org/wiki/Norovirus

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(I mixed up the classification and cell structure weeks, so I'm doing classification this week)

Norovirus is classified into 10 capsid genogroups (GI-GX)

Each genogroup varies in amino acid sequence, but all encode for the capsid gene (VPI)

Not all the genogroups cause disease, but the GI, GII and GIV are pathological to humans

Resources:

https://www.ncbi.nlm.nih.gov/books/NBK513265/

https://www.sciencedirect.com/topics/immunology-and-microbiology/norovirus

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When Norovirus is infected within a host cell, it alters the cells metabolism by changing lipid biosynthesis and metabolic pathways to have it work in it’s advantage

It changes lipid biosynthesis by changing the lipid membrane structure in the cell by having it work for it’s advantage of spreading the disease to other cells

Norovirus essentially reprograms the metabolic pathways of the cell by increasing it’s glycolysis, oxidative phosphorylation, and pentose phosphate pathway

These pathways allow the host cell to remain infected with the virus and spread it to other cells, increasing it's transmission

When metabolism within the host cell is inhibited, viral replication is as well-indicating that metabolism, specifically glycolysis, is a key factor in the ability for the virus to spread to other cells

The image shows the structure of a healthy cell in comparison with the virally infected cell

The tropism of Norovirus are epithelial and non-epithelial cells, specifically immune cells (macrophages, dendritic cells, B and T lymphocytes) and intestinal cells (gut-associated lymphoid tissue)

Resources:

https://biologyinsights.com/norovirus-life-cycle-entry-replication-and-transmission/

https://pubmed.ncbi.nlm.nih.gov/30862747/

https://en.wikipedia.org/wiki/Gut-associated_lymphoid_tissue

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Norovirus is a highly contagious virus responsible for acute gastroenteritis, affecting millions worldwide each year. Its rapid spread and ability to cause outbreaks in various settings make understanding its life cycle essential for developing effective prevention and treatment strategies.

This article explores the norovirus life cycle, covering stages such as viral entry, genome replication, protein synthesis, host cell interaction, and how it exits the host cell to ensure transmission to new hosts.

Viral Entry

Norovirus infection begins with its entry into the host cell, a process that is both intricate and specific. Norovirus primarily targets the epithelial cells of the small intestine, exploiting the host's cellular machinery to gain entry. This process is facilitated by the virus's ability to bind to histo-blood group antigens (HBGAs) on the surface of these cells. These antigens act as receptors, allowing the virus to attach securely and initiate the entry process. The specificity of this interaction influences susceptibility, as variations in HBGA expression can affect infection rates.

Once attached, the virus employs endocytosis, a cellular mechanism that allows it to be engulfed by the host cell. This method enables the virus to bypass the host's external defenses and enter the intracellular environment where it can begin replication. The endocytic pathway involves the invagination of the cell membrane, forming a vesicle that encapsulates the virus and transports it into the cell's interior. This vesicular transport ensures the virus is delivered to the appropriate cellular compartment for subsequent uncoating and replication.

Genome Replication

After entering the host cell, norovirus begins genome replication in the cytoplasm, where the viral RNA is released and serves as a template. The norovirus genome is a positive-sense, single-stranded RNA, which allows it to be directly translated by the host's ribosomes. This immediate translation facilitates the production of viral proteins necessary for replication.

To replicate its RNA genome, the virus encodes an RNA-dependent RNA polymerase (RdRp). This enzyme synthesizes a complementary negative-sense RNA strand, which then acts as a template for producing new positive-sense RNA genomes. The replication complex, composed of viral and host proteins, assembles within membrane-associated compartments derived from the endoplasmic reticulum. These compartments provide an environment for replication, shielding the process from cellular defense mechanisms.

Protein Synthesis

Once norovirus has established its replication machinery, the next phase is protein synthesis. The positive-sense RNA genome of norovirus acts as a messenger RNA (mRNA), recognized by the host cell's ribosomal machinery, setting the stage for the synthesis of viral proteins.

Norovirus employs a strategy of polyprotein synthesis, wherein a single, large polyprotein is translated from the RNA. This polyprotein undergoes a series of cleavages by viral proteases, enzymes that the virus encodes specifically for this purpose. These proteolytic cleavages result in the liberation of functional viral proteins, including structural components like capsid proteins and non-structural proteins vital for replication and assembly. The efficiency of this protein synthesis strategy allows the virus to maximize resource use and streamline the production of its necessary components.

The host cell's machinery is co-opted to ensure that protein synthesis is both rapid and efficient. During this process, the virus alters the host's cellular environment, creating optimal conditions for its own protein production while minimizing the cell's ability to mount an effective defense. This manipulation of cellular pathways demonstrates the virus's evolutionary adaptation, enabling it to thrive within the host.

Host Cell Interaction

The interaction between norovirus and its host cell involves molecular manipulation and adaptation. Once inside, norovirus hijacks the host's cellular processes, steering them towards viral replication and assembly. The host cell responds by activating various signaling pathways in an attempt to counteract the viral invasion. The virus, in turn, has evolved strategies to evade these defenses, creating a dynamic interplay that influences the course of infection.

Norovirus affects cellular metabolism to its advantage, altering lipid biosynthesis pathways to create membrane structures that facilitate viral replication. These alterations assist in creating viral replication compartments and help in evading host immune detection. The virus also modulates host cell apoptosis, or programmed cell death, to prolong cell survival and ensure sufficient time for replication and assembly of new virions.

Viral Egress and Transmission

As norovirus completes its replication and assembly within the host cell, it must efficiently exit to infect new cells and hosts. The process of viral egress is a finely tuned mechanism that ensures the successful dissemination of viral particles. Norovirus employs a non-lytic release strategy, preserving host cell integrity while allowing virions to exit and spread. This method involves the use of cellular vesicles that transport assembled virions to the cell's surface, where they are released into the extracellular space.

The transmission of norovirus is primarily fecal-oral, occurring through direct contact, contaminated surfaces, or ingestion of tainted food and water. The virus's resilience in diverse environments and its ability to withstand varying temperatures contribute to its widespread dissemination. Norovirus particles can remain infectious on surfaces for extended periods, highlighting the challenges in curbing its spread. The low infectious dose required to cause illness further complicates control measures, as even minimal exposure can lead to outbreaks.

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Norovirus Life Cycle: Entry, Replication, and Transmission

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Explore the intricate processes of norovirus entry, replication, and transmission within host cells, highlighting key interactions and mechanisms.

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The growth requirements of Norovirus are as follows:

Small inoculum

Norovirus can spread easily and quickly due to the small inoculum that is needed for infection

Viral shedding

Depends on the duration of time that the infected indiviudal can spread Norovirus to others

Can remain on contaminated foods and sufaces for several weeks, but peaks at around 2-5 days

Environments

Anaoroic solution

Doesn't require oxygen for growth

Salt water

Can survive for up to 3 weeks

Temperature

Can survive in cold temperatures and hot temperatures

pH

Optimal growth of Norovirus occurs within a pH of 3 to 7, making in an acidophile

Genetically encoded host factors:

Blood type

Individuals with blood type B have partial protection from Norovirus strains- people who don't have histo-blood group antigen (HBGAG)

Blood type A, AB and O are more suseptible to norovirus

FUT-2 gene

Individuals with this gene show greater susptibility to virus

Gene encodes for enzyme that synthesizes the H-1 antigen in saliva and mucus

Best way to grow norovirus:

Human bile acid culture

Acidophile (pH 3-7)

Study of strain-specific growth requirements of human enteroids

The graph shows the growth of Norovirus in an environment of bile acid and an environment of non-bile acid

Human intestinal epithelial cells

Where virus grows in the small intestine

Site of infection

Contaminated food

Contaiminated water

Contaiminated surfaces

Media for growth

Difficult to culture in vitro becasue of the epithelial cell type specificity needed for growth and lack of animal models, but recently stem-cell derived human intestinal enteroid became available

Resources:

https://pmc.ncbi.nlm.nih.gov/articles/PMC6669637/

https://pmc.ncbi.nlm.nih.gov/articles/PMC7885322/

https://pmc.ncbi.nlm.nih.gov/articles/PMC4284304/

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Human Norovirus Cultivation in Nontransformed Stem Cell-Derived Human Intestinal Enteroid Cultures: Success and Challenges

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Noroviruses, in the genus Norovirus, are a significant cause of viral gastroenteritis in humans and animals. For almost 50 years, the lack of a cultivation system for human noroviruses (HuNoVs) was a major barrier to understanding virus biology and…

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Norovirus consists of a single-stranded RNA molecule as its genetic material

Since plasmids exist inside bacteria and not viruses, Norovirus does not contain any plasmids

Antibiotic resistance genes are not found in Norovirus since antibiotics do not have any effect on viruses

The genome of Norovirus has been mapped and is 7.5 to 7.7kb in length and is organized into three (can sometimes be four) open reading frames (ORF), as shown in the data

Resource:

https://pmc.ncbi.nlm.nih.gov/articles/PMC4178781/table/T6/

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Deep Sequencing of Norovirus Genomes Defines Evolutionary Patterns in an Urban Tropical Setting _ Journal of Virology

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The virulence factors of Norovirus are composed of VP1 and VP2

VP1 is the major capsid protein, making up the outer shell, and VP2 is the minor capsid protein, forming the inner layer of the Noroviruses capsule

Since Norovirus is a virus and not a bacteria, it does not contain any antiobiotic resistant genes and are not considered toxins. However, VP1 and VP2

Since VP1 and VP2 act its structural component, these proteins can help in the viruses ability to infect it's host cell, by first binding to histo-blood group antigens (HGGAs) and allowing entry into it's target cell

In terms of virulence factor 1 (VF1), exoenzymes can help pathogens to invade their host cell by getting released outside the cell, with their primary role being to breakdown larger molecules so absorbance by the cell can occur.

Norovirus envades the immune system by antagonizing cytokine induction to it's host cell, ultimately suppressing it's release of cytokins which are molecules that regulate activity of other immyne cells toward the location of viral infection

Antigenic variation of Norovrius is driven by mutations in the major capsid protein (VP1), allowing the virus to envade host cells more readily by suppressing immune response

The image shows how Noroovirus protein can suppress cytokine induction when VP1 (viral capsid protein) attatches to VF1 (viral factor 1)

Resources

https://pubmed.ncbi.nlm.nih.gov/22615565/

https://pmc.ncbi.nlm.nih.gov/articles/PMC4821668/

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Biochemical testing that is done on Norovirus is most commonly done through reverse transcriptase- polymerase chain reaction (RT-PCR)

Norovirus is positive for the viral antigen or viral RNA picked up from real time RT-PCR assay

Since Norovirus is a virus and not a bacteria, it isn't positive for phenol red, IMViC, catalase, oxidase and ETC biochemical testing

Instead, RT-qPCR (as previously menthioned), enzyme immunoassays (EIA) and electron-microscopy (EM) are the methods usually used when testing for the genetic material or viral antigen of Norovirus

Resources:

https://www.cdc.gov/norovirus/php/laboratories/index.html

https://pubmed.ncbi.nlm.nih.gov/2822438/

https://microbenotes.com/imvic-tests/

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Learn about lab testing and diagnostic methods for norovirus.

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As previously mentioned in biochemical tests used to detect Norovirus, RT-qPCR assay's are the preferred method for the diagnosing of Norovirus

RT-qPCR is the preferred method due to its sensitivity in detecting the virus through only a few copies of RNA genetic material or viral antigens needed to show a positive result

RT-qPCR is also very specific, providing information to microbiologist's performing the test on what genogroup (GI or GII) the patient's Norovirus falls into

Another reason it's the preferred method, is due to it's rapid testing- getting results in as little as 30 minutes

RT-qPCR stands for reverse transcription (using RNA to detect genetic material of virus), quantifiable (quantifying gene expression, RNA, and viral pathogen levels), polymerase chain reaction (used to ampify and detect specific viral target- Norovirus)

Another diagnostic test used for detecting Norovrius is is EIA which stands for enzyme immunoassay, which is only used when there is a rise in cases, impacting multiple people in a specific area (outbreak), but should only be used on top of RT-qPCR.

Resources:

https://www.thermofisher.com/us/en/home/brands/thermo-scientific/molecular-biology/molecular-biology-learning-center/molecular-biology-resource-library/spotlight-articles/basic-principles-rt-qpcr.html

https://www.mayoclinic.org/diseases-conditions/norovirus/diagnosis-treatment/drc-20355302

https://www.cdc.gov/norovirus/php/laboratories/index.html

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Basic Principles of RT-qPCR | Thermo Fisher Scientific - US

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Introduction to quantitative reverse transcription PCR (RT-qPCR)—used in a variety of applications including gene expression analysis, RNAi validation, and more.

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Norovirus is directly transmitted through person to person contact with the infected individual through contact with their skin (skin-on-skin contact) or by accidentally getting infected by their feces (fecal-oral route)

Indirect contact of Norovirus is through viral particles being expelled by a infected person to another individual through inhalation of viral particles- exposing a new individual to virus

Indirect transmission of Norovirus is also acquired through ingesting contaminated food or touching contaminated surfaces that are infected by the virus

Fomites are objects that can be infected by the agent Norovirus through contaminated surfaces (tables, door knobs, etc.)

Vectors of Norovirus are through getting tiny fece or vomit particles in exposed individuals mouth

Resources:

https://pmc.ncbi.nlm.nih.gov/articles/PMC4624335/

https://www.cdc.gov/infection-control/hcp/norovirus-guidelines/background.html

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✉Corresponding author: B. Lopman, 1600 Clifton Road Atlanta, GA 30333, USA blopmancdc.gov

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Norovirus infections are notoriously difficult to prevent and control, owing to their low infectious dose, high shedding titre, and environmental stability. The virus can spread through multiple transmission routes, of which person-to-person and…

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The pathology of Norovirus shows up through the following symptoms (what the patient is experiencing internally) and signs (what is externally apparent to others):

Symptoms:

Stomach pain

Nausea

Body aches

Fatigue

Dehydration

Signs:

Vomiting

Diarrhea

Fever

Damage done by Norovirus:

Leading cause of gastrointestinal illness in the united states

Causes 58% of food-borne illnesses

Person-to-person contact is usually how the virus spreads, but contaminated surfaces also spread Norovirus as well

Vaccination and proper aseptic techniques and precautionary measures taken in hospitals inhibit the spread of Norovirus

In healthy individuals, they can usually recover from the illness in 3-5 days without any intervention, but for chilrden, immunocompromised individuals and the elderly, staying in a hospital may need to occur to prevent dehydration and promote a full recovery

The immune response of Norovirus occurs through the following physiological processes within the body:

At the site of infection, cytokines trigger inflammatory response and recruit immune cells (lymphocytes, macrophages, dendritic cells, etc.) to be up-regulated to fight the virus

Norovirus does not rely on antibodies, making it a virus that triggers a cell-mediated response to fighting infection by utilizing T cells (T lymphocytes) and other immune cells to get rid of the antigen (Norovirus)

Humeral immunity relies mainly on antibodies to get rid of the antigen, specifically B cells (B lymphocytes), since Norovirus relies on immune cells more than antibodies, it doesn't elicit this immune response (humeral or antibody-mediated response) like it does for the cell-mediated immune response

Norovirus is usually acute, but in immunocompromised individuals, it can become chronic. However, it doesn't seem to cause an autoimmunity post-infection, which is when the body mistakes it's own healthy cells for an invaders and destroys them.

Resources:

https://www.mayoclinic.org/diseases-conditions/norovirus/symptoms-causes/syc-20355296

https://www.nature.com/articles/s41564-017-0057-7

https://pmc.ncbi.nlm.nih.gov/articles/PMC6630345/

https://pmc.ncbi.nlm.nih.gov/articles/PMC4793940/

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Overview

Norovirus infection can cause the sudden onset of severe vomiting and diarrhea. The virus is highly contagious and commonly spread through food or water that is contaminated during preparation or through contaminated surfaces. You can also be infected through close contact with an infected person.

Diarrhea, stomach pain and vomiting typically begin 12 to 48 hours after exposure. Norovirus symptoms usually last one to three days, and most people recover completely without treatment. However, for some people - especially infants, older adults and people with underlying disease - vomiting and diarrhea can be severely dehydrating and require medical attention.

Norovirus infection occurs most frequently in closed and crowded environments such as hospitals, nursing homes, child care centers, schools and cruise ships.

Symptoms

Signs and symptoms of norovirus infection include:

Nausea

Vomiting

Stomach pain or cramps

Watery or loose diarrhea

Feeling ill

Low-grade fever

Muscle pain

Signs and symptoms usually begin 12 to 48 hours after exposure to norovirus and last one to three days. You can continue to shed virus in your feces for up to two weeks after recovery. This shedding can last weeks to months if you have an underlying health condition.

Some people with norovirus infection show no signs or symptoms. However, they are still contagious and can spread the virus to others.

When to see a doctor

Seek medical attention if you develop diarrhea that doesn't go away within several days. Also, call your doctor if you have severe vomiting, bloody stools, stomach pain or dehydration.

Causes

Noroviruses are highly contagious and are shed in the feces of infected humans and animals. You can get norovirus by:

Eating contaminated food

Drinking contaminated water

Touching your hand to your mouth after your hand has been in contact with a contaminated surface or object

Being in close contact with a person who has a norovirus infection

Noroviruses are difficult to kill off because they can withstand hot and cold temperatures and most disinfectants.

Risk factors

Risk factors for becoming infected with norovirus include:

Eating in a place where food is handled improperly

Attending preschool or a child care center

Living in close quarters, such as in nursing homes

Staying in hotels, resorts, cruise ships or other destinations with many people in close quarters

Having contact with someone who has norovirus infection

Complications

For most people, norovirus infection usually clears up within a few days and isn't life-threatening. But in some people - especially children, older adults and people with compromised immune systems - norovirus infection can cause dehydration. Norovirus infection can cause severe dehydration, malnutrition and even death, especially in people who are older or immunocompromised, or in women who are pregnant.

Warning signs of dehydration include:

Fatigue

Dry mouth and throat

Listlessness

Dizziness

Decreased urine output

Children who are dehydrated might cry with few or no tears. They might be unusually sleepy or fussy.

Prevention

Norovirus infection is highly contagious, and anyone can become infected more than once. To help prevent its spread:

Wash your hands thoroughly with soap and water, especially after using the toilet or changing a diaper.

Avoid contaminated food and water, including food that could have been prepared by someone who was sick.

Wash fruits and vegetables before eating.

Cook seafood thoroughly.

Dispose of vomit and fecal matter carefully to avoid spreading norovirus by air. Soak up material with disposable towels, disturbing it as little as possible, and place it in plastic disposable bags.

Disinfect surfaces that might have been contaminated. Use a chlorine bleach solution and wear gloves.

Stay home from work, especially if your job involves handling food. You might be contagious for as long as three days after your symptoms end. Children should stay home from school or child care.

Avoid traveling until your signs and symptoms are gone.

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Norovirus infection - Symptoms and causes

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Norovirus infection can cause the sudden onset of severe vomiting and diarrhea. The virus is highly contagious and commonly spread through food or water that is contaminated during preparation or through contaminated surfaces. You can also be infected through close contact with an infected person.

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Depending on the health of ones immune system, a full recovery can be achieved through resting for a few days and rehydration of fluids lost through vomiting and diarrhea by drinking plenty of fluids to restore electrolytes

However, those with a compromised immune systems may require more extensive treatment protocols in order to recover from Norovirus, including through anti-microbial medication and immunoglobulin therapy

Some anti-viral and immunoglobulin treatments have proven to be ineffective, such as through the anti-microbial drug ribovirin, and through taking oral immunoglobulins

Other chemotherapy treatments have been proven to be successful, like through the anti-viral drug Nitazoxanide, which has provided relief to patients suffering from constant, severe diarrhea to reduce output- allowing for the fluids and electrolytes that would've been lost, to be restored.

While oral immunoglobulins aren’t effective, intravenous immunoglobulins (IVIG) therapy, which has provided patients suffering from immunodeficiency diseases to experience a faster recovery time, so that Norovirus does not become chronic

Using anti-viral medication and immunoglobulin IV chemotherapy treatments allows for individuals unable to recover from the virus within a few days through rest and rehydration a faster recovery time, reducing the chances that the virus becomes chronic, however, they do come with side effects:

Anti-viral medication (Nitazoxanide):

Nausea

stomach pain

vomiting

Immunoglobulin IV administration:

Fever

Chills

Headaches

This is why chemotherapy treatments are only used in those who's immune systems aren't strong enough to recover from the virus by time (a few days), rest and rehydration (water and electrolytes) due to immunodeficiency and severe, constant diarrhea

Generally, recovery is achieved through:

Nitazoxanide:

Using 500mg/twice daily for seven day to fourteen days.

Immunoglobulin IV treatment:

Administering 25mg/kg for three consecutive days.

Resources:

https://my.clevelandclinic.org/health/diseases/17703-norovirus

https://pubmed.ncbi.nlm.nih.gov/31999825/

https://ashpublications.org/blood/article/122/21/4581/11274/Nitazoxanide-Is-Effective-Therapy-For-Norovirus

https://pmc.ncbi.nlm.nih.gov/articles/PMC9413339/

https://www.annallergy.org/article/S1081-1206(20)30855-3/abstract

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Intelligent search from Bing makes it easier to quickly find what you're looking for and rewards you.

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Norovirus is the leading cause of acute gastroenteritis outbreaks world-wide

Gastroenteritis is the inflammation and of the mucous membranes lining digestive tract, leading to nausea, vomiting and diarrhea

Outbreaks can occur throughout the year but most commonly occur between November-April

Since Norovirus is extremely contagious and can be spread through person-to-person contact, contaminated surfaces and contaminated foods, it has the ability to become an epidemic or pandemic

To classify a disease as an epidemic, there must be an increase in the number of cases than expected for a particular area. In January of 2025, the CDC stated that Norovirus cases have doubled what they were this time last year in the US, making Norovirus fall under the classification of an epidemic.

During COVID-19, Norovirus cases fell to an all time low, indicating that the protective measures of significantly reducing person-to-person contact helped reduce the spread of Norovirus. Therefore, Norovirus has the potential of becoming a pandemic as well if people don't stay home when they are sick, clean surfaces and practice proper food preparing techniques.

Prevalence rate is determined by comparing the number of people infected with the disease to the number of people in the entire population for a specific period of time.

Worldwide, there are an estimated 685 million Norovirus cases annually

In the US, an average of 2,500 cases are reported to the CDC per year. This number doesn't reflect the estimated amount of people infected with the virus, which is much higher-which is estimated to be closer to 20 million morbidity rate.

The mortality of Norovirus is close to 200,000 death per year worldwide, especially in impoverished nations, the elderly and immunocompromised populations.

In the US, the mortality rate of Norovirus is 900 deaths/year

Resources:

https://www.fastcompany.com/91261028/norovirus-outbreak-2025-symptoms-cases-cdc-data-update

https://www.today.com/health/disease/norovirus-2025-rcna185976

https://pmc.ncbi.nlm.nih.gov/articles/PMC3118882/

https://www.cdc.gov/norovirus/outbreak-basics/index.html

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Norovirus outbreak 2025: Symptoms, cases, and what to know as CDC data indicates a winter wave

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New CDC data indicates a rise in cases of norovirus, often colloquially referred to as “stomach flu.” Test positivity has spiked.

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In 1968, there was a Norovirus outbreak in a hotel. It was originally assumed that the spread of the virus occur mostly through airborne transmission but was hypothesized that the fomite transmission might have cause the spread of the virus just as much as through close contact with others. The results showed that yes indeed, the fomite transmission rate plays a big part in the spread of the virus, along with the airborne transmission rate.

Resources:

https://www.mdpi.com/1660-4601/14/12/1571

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Airborne or Fomite Transmission for Norovirus? A Case Study Revisited

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Norovirus infection, a highly prevalent condition associated with a high rate of morbidity, comprises a significant health issue. Although norovirus transmission mainly occurs via the fecal-oral and vomit-oral routes, airborne transmission has been proposed in recent decades. This paper re-examines a previously described norovirus outbreak in a hotel restaurant wherein airborne transmission was originally inferred. Specifically, the original evidence that suggested airborne transmission was re-analyzed by exploring an alternative hypothesis: could this outbreak instead have occurred via fomite transmission? This re-analysis was based on whether fomite transmission could have yielded similar attack rate distribution patterns. Seven representative serving pathways used by waiters were considered, and the infection risk distributions of the alternative fomite transmission routes were predicted using a multi-agent model. These distributions were compared to the reported attack rate distribution in the original study using a least square methods approach. The results show that with some reasonable assumptions of human behavior patterns and parameter values, the attack rate distribution corresponded well with that of the infection risk via the fomite route. This finding offers an alternative interpretation of the transmission routes that underlay this particular norovirus outbreak and an important consideration in the development of infection control guidelines and the investigation of similar norovirus outbreaks in future.