Realm	Riboviria
Kingdom	Orthornavirae
Phylum	Pisuviricota
Class	Pisoniviricetes
Order	Picornavirales
Family	Caliciviridae
Genus	Norovirus
Species	Norwalk virus

Norwalk Virus (Norovirus)

• Norovirus, an RNA-based virus belonging to the family Caliciviridae is an enteric pathogen that can cause significant morbidity and mortality in health medical and communities.
• Norovirus, also known as winter vomiting bugs is the most frequent cause of gastroenteritis.
• The symptoms of the infection are vomiting, diarrhea that isn’t bloody as well as stomach pain. Also, headaches or fevers could be a sign of the infection.
• Symptoms typically manifest 12 to 48 hours after exposure The majority of patients recover within one to three days.
• The most common complications are those that could include dehydration, especially for the young, the elderly, and people with other health issues.
• It can be spread easily through food and drinks and can have a huge effect the people’s health.
• The original name was the Norwalk virus, in reference to Norwalk, Ohio. Norwalk, OH, where the first outbreak of the virus was reported in 1972.
• On average, noroviruses trigger 19 millions instances of gastroenteritis acute in U.S. per year and cause nearly 450,000 people to the emergency department as per the CDC. They are responsible for more than 50% of all food-borne disease outbreaks every year. There are a variety of noroviruses. Exposure to one kind of virus might not be enough to protect you from other types.
• While norovirus is a threat all year round however, it’s more common during the winter months. Some call it”the “winter vomiting virus.”
• Noroviruses can also be referred to as food poisoning due to the fact that they can spread by eating food that is contaminated. They’re not always caused by contamination of food, however.

The Symptoms of Norwalk Virus (Norovirus)

The most commonly reported symptoms of norovirus are:

• diarrhea
• vomiting
• nausea
• stomach pain

Other symptoms may include:

• fever
• headache
• body aches

Norovirus is a cause of inflammation in the stomach or the intestines. This is referred to as acute gastroenteritis.

It is common for a person to develop symptoms within 12 to 48 hours after exposure to norovirus. The majority of people suffering from norovirus disease are cured within a few days.

If you suffer from norovirus it is possible to feel sick and have diarrhea or vomiting often throughout the day. This could cause dehydration, particularly for children who are young, older adults and people who suffer from other ailments.

The signs of dehydration are:

• less frequent urine production
• Dry throat and mouth
• getting dizzy while getting up
• Kids who have dehydration might cry without or with very few tears, and may be extremely tired or irritable.

Transmission of Norovirus

If you contract norovirus there are millions of norovirus particles cannot be seen without the aid of a microscope. A handful of norovirus particles could make others people sick. You’re the most infectious

• If you experience symptoms of norovirus infection particularly vomiting
• within those first couple of days following the recovery from norovirus.

But, studies have shown that you could still contract norovirus for up to two weeks after feeling better.

Norovirus spreads through contaminated food

Norovirus is a common cause of contamination in food items as well as water since it needs a tiny quantity of viruses to cause someone sick. Food items and water could be affected by norovirus in a variety of ways, for example:

• Infected people touch food items with their naked hands and then they ingest Feces (poop) or vomiting particles on them.
• Food items are placed on the counter or on a surface which has vomit or feces particles on it.
• Small drops in vomit from the affected person are sprayed into the air, and then land on food items.
• The food is either grown or harvested using contamination of water like oysters that are harvested from contamination water or even fruit and vegetables irrigated using water that is contaminated water on the fields.

Norovirus spreads through contaminated water

Drinking or recreational water may be contaminated with norovirus, which can cause illness or cause food poisoning. It can occur:

• At the point of origin, for instance when the septic tank leaks in the well.
• Infected people vomit or vomits into the water.
• If water isn’t properly treated, for example, if there isn’t enough chlorine.

Norovirus spreads through sick people and contaminated surfaces

Surfaces can be infected with norovirus in various ways, including:

• A person infected is able to touch the surface using their hands and is covered with Vomit or feces on their hands.
• The person with the infection is prone to vomiting or diarrhea, which spills out onto surfaces
• Water, water, or objects that have been infected with norovirus are put on the floor
• The tiny particles of vomit fly through the air before landing on the floor or into the mouth of an individual, after which the person swallows it.

Prevention of Norwalk Virus (Norovirus)

You can protect you and your loved ones from Norovirus through cleaning all your hands well with soap and water and by following other simple preventive tips.

1. Practice proper hand hygiene

Cleanse your hands thoroughly using soap and water

• particularly after using the bathroom or changing diapers
• Always before eating, cooking or handling food and
• prior to giving yourself or anyone else medicine.

The virus can be detected in the feces or vomit (poop) prior to the time you begin feeling sick. The virus may also remain within your stool for up to two weeks or more once you are feeling better. It is essential to keep cleaning your hands frequently throughout this time.

It is possible to use hand sanitizers as well as hand washing, however you shouldn’t make use of hand sanitizers to wash your hands thoroughly with hot water along with soap. Hand washing is the best option.

2. Handle and prepare food safely

Wash your fruits and vegetables thoroughly before cooking for eating. Make sure to cook oysters as well as other seafood in a thorough manner in advance of eating them.

Take note that noroviruses can be immune to heat. They can tolerate temperatures up to 145 degrees F. The quick steaming methods commonly used to cook shellfish can’t heat enough to kill noroviruses.

Foods that could be infected by norovirus must be thrown away. Make sure that sick children and infants are kept away from areas where food preparation and handling is occurring and cooked.

3. When you are sick, do not prepare food or care for others

It is not recommended to prepare food for others or offer health care during your illness and for at least 2 days following symptoms cease. This is also true for employees who are sick at restaurants, schools daycares, long-term care establishments, and other areas that could risk exposing people to norovirus.

4. Clean and disinfect surfaces

When someone vomits or experiences diarrhea, ensure that they thoroughly clean and disinfect the entire area right away. Put on disposable or rubber gloves and clean the entire area using paper towels. Then clean the area with bleach-based household cleaners according to the instructions indicated on the label of the product. The bleach disinfectant should be left on the area affected for at minimum five minutes, and then wash the entire area by using detergent and warm water. Clean up soiled laundry and garbage and washing your hands.

To ensure that food preparation is free of norovirus, regularly wash and sanitize kitchen appliances as well as counters and surfaces prior to preparing food.

You should choose bleach with chlorine at an amount of between 1,000 and 5 mg (5 up to 25 teaspoons bleach from the household [5 percent or 8%] for each gallon water) or another disinfectant that has been certified for its effectiveness against norovirus from the Environmental Protection Agency (EPA).

5. Wash laundry thoroughly

Remove and wash immediately clothing or linens that might contain urine or Feces.

You ought to:

• Be careful when handling soiled objects without shaking (shaking) them.
• Wear disposable or rubber gloves while handling objects that are soiled, and clean your hands after washing your hands, and
• Wash the item with the detergent (cleaning agents) as well as hot water at the longest cycle length , and then dry them using the top heat setting.

Treatment of  Norwalk Virus (Norovirus)

• If you suffer from norovirus You should drink plenty of fluids to replenish the fluid lost through diarrhea and vomiting. This can help to prevent dehydration.
• Dehydration can cause serious health issues. Dehydration that is severe may need hospitalization to treatment by administering fluids via your vein (intravenous or IV fluids).
• Look for indicators of dehydration among children with norovirus infection. The children who have dehydration might cry, but with fewer or no tears and appear to be tired or fussy.
• If you believe you or someone you’re taking care of is dehydrated to the extreme Contact your healthcare professional.

Structure of Norwalk Virus (Norovirus)

• The virus is un-enveloped, round, 27-nm particles with a rough outer edge, but without a specific surface structure.
• It has a floating density of 1.33-1.41 g/cm3 and an inability to reproduce in vitro.
• In terms of its characteristics, Norwalk virus has only one capsid protein.
• Genome is non-segmented single-stranded, positive-polarity the RNA genome.
• A prominent spike of ten and 32 cup-shaped depressions be observed in the virion using microscopy.
• Capsid’s structure is divided into two domains that are joined by a hinge that is flexible.
• The shell (S) domain is comprised of 225 N-terminal amino acids and plays a role in the creation of the capsid’s icosahedral shell.
• A protruding (P) domain is one of the most prominent structures that extend outwards from the shell. It’s made up of the C-terminal portion that makes up the protein.
• The domain P is divided in two distinct domains (P1 and P2) and it is believed that these structures could be involved in binding cell receptors, and could be the main determinants of strain specificity.

Genome of Norwalk Virus (Norovirus)

• The RNA genome (monopartite the linear and ssRNA(+) genome of 7.3 to 8.3 kb) of the Norwalk virus is divided into three main open-reading frames (ORF1 2, 3) with the 3′-end being polyadenylated.
• ORF1 encodes a massive polyprotein composed of three regions, each containing non-structural protein motif.
• The ORF2 encodes for the primary capsid protein.
• ORF3 encodes a protein that is the basis of.
• The VPg covalently connects to the 5′-end of the positively-stranded RNA genome.

Epidemiology of Norwalk Virus (Norovirus)

• Human caliciviruses have a global distribution.
• Norwalk virus is the largest frequent cause of nonbacterial gastroenteritis the United States, causing an estimated 21 million cases each year.
• Norwalk virus is now recognized as the main reason for the emergence of non-bacterial cases of gastroenteritis in the world.
• The national surveillance system and the diagnosis EM of nonbacterial outbreaks gastroenteritis within the UK have demonstrated the fact that Noroviruses (Norwalk virus) is a more frequent cause of gastroenteritis with an infection over Salmonella and Campylobacter (Food Standards Agency 2000).).
• There has been an increase in Norwalk virus in the last few years with a clear evidence of a winter season leading to a massive outbreak across the UK in January 2002.
• In the same way, since October 2002, an array of states within the USA have seen an increase in the number of cases of Norovirus disease.
• This virus was the cause of an outbreak that spread across the entire community in Norwalk, Ohio.
• The subsequent surveillance and investigation of outbreaks in a variety of regions of the world revealed the potential of Noroviruses for causing a rash of gastroenteritis in community-wide or semiclosed populations, such as families, health institutions as well as holiday destinations such as cruise vessels, education establishments and even the catering sector.
• Infections can be found in children as well as adults, but not often in neonates or very young children.
• Norovirus outbreaks are expected to hit Kerala in 2021. The incident was reported by 13 students at an veterinary school in Pookode. 

Diagnosis of Norwalk Virus (Norovirus)

• The isolation of the virus is facilitated by transmitting Norwalk virus in chimpanzees where serological responses and the excretion of Norwalk virus antigens in stools were observed.
• Use of RT-PCR in the analysis of the genome within stool samples or emesis specimens.
• Immunoelectron microscopy is a method to identify and concentrate the virus within the stool.
• The presence of an antibody that targets the suspect agent can cause the virus to accumulate which makes it easier to recognize.
• ELISA tests were created to identify the virus, antigen of the virus, as well as antibodies to the virus.
• The tests ELISA as well as RIA are serodiagnostic tests that are commonly employed to determine specific antibodies against Norwalk virus in serum.

Pathogenesis of Norwalk Virus (Norovirus)

• The virus is introduced into the body most often through an oral pathway.
• They are acid-stable, and are which is consistent with their ability to withstand passage through the stomach. Replication is found inside the jejunum.
• A mere 10 viruses will cause disease for humans.
• Infection of the border of the intestinal tract hinders the absorption of water and nutrients, and can cause diarrhea with water.
• A partial flattening and widening of villi, with disorganization of mucosal epithelium.
• Lamina propria was infiltrated with mononuclear cell vacuolization and mucosal epithelium.
• Crypt cells hyperplasia is quite common.
• The smooth and rough ER and an increase in the number of multivesicular bodies on mucosal epithelial cells.
• Microvilli were significantly reduced and amorphous electron-dense was found in the intercellular spaces that were expanded.
• The virus’s sheds can last for up to 2 weeks after symptoms have subsided.
• It is a common occurrence that immunity is short-lived. might not provide protection.

Replication of Norwalk Virus (Norovirus)

• Norwalk virus infects the body mostly through orally route.
• They are acid-stable, and are in line with their capacity to withstand passage in the stomach.
• The virion triggers infection through binding to the receptor of the cell on the cell membrane. It then get into the cell.
• Receptor binding triggers changes in conformation that results in the release of RNA from viruses into the cell’s the cytoplasm.
• VPg is eliminated from the viral RNA.
• Positive stranded RNA functions as mRNA and genome for these viruses. It is transformed into a polypeptide referred to as non-capsid virus protein.
• In turn, the viral protein is used by the viral enzyme protease in order to create capsid protein of the progeny and other non-capsid proteins like the polymerase RNA.
• The RNA polymerase is the catalyst for the synthesis of the RNA genomes of progenitors.
• The virus that causes infection is copied and the corresponding one serves as a template to create new and additional strands.
• Subgenomic RNA is an example that allows the transcription of capsid and the ORFs that are terminal.
• The replication process is followed by packing of strands that are plus into virions, and maturation requires multiple cleavage steps.
• The progeny virion formation is accomplished through a layering of genomic RNA that is bonded to the capsid protein within the cell’s cytoplasm. This process is called encapsidation.
• Release of the progeny virions is caused due to the lysis of a cell.

FAQ

References

• Blacklow NR. Norwalk Virus and Other Caliciviruses. In: Baron S, editor. Medical Microbiology. 4th edition. Galveston (TX): University of Texas Medical Branch at Galveston; 1996. Chapter 65. Available from: https://www.ncbi.nlm.nih.gov/books/NBK8545/
• Robilotti E, Deresinski S, Pinsky BA. Norovirus. Clin Microbiol Rev. 2015 Jan;28(1):134-64. doi: 10.1128/CMR.00075-14. PMID: 25567225; PMCID: PMC4284304.
• https://www.cdc.gov/norovirus/index.html
• https://www.health.ny.gov/diseases/communicable/norwalk/fact_sheet.htm
• https://www.webmd.com/food-recipes/food-poisoning/norovirus-symptoms-and-treatment
• https://my.clevelandclinic.org/health/diseases/17703-norovirus
• https://www.health.state.mn.us/diseases/norovirus/noro.html