Norovirus Infection and its Consequences

Introduction:

Human norovirus, previously called Norwalk virus, was first determined in stool specimens collected during an outbreak of gastroenteritis in Norwalk and is the first virus to cause gastroenteritis. The illness caused by this virus was earlier described as winter vomiting disease in 1929 due to seasonal preference, and most patients presented with vomiting as a primary symptom. The HuNoV infection results in 699 million illnesses and 219,000 deaths yearly. Unfortunately, no vaccine is available to prevent norovirus infections.

What Is Norovirus?

Norovirus or Norwalk virus belongs to the family Calciviridae. It is known to cause ‘winter-vomiting disease’ or stomach flu due to its rapid spread in human populations during winter. Norovirus causes gastroenteritis in humans and is a group of viruses and variants. The illness of norovirus is brief among healthy individuals. However, children, the elderly, and immunocompromised people are at a higher risk of developing a severe or prolonged infection. These infections spread rapidly and cannot be treated with antibiotics, like other viral infections.

What Are the Manifestations of Norovirus Infection?

Asymptomatic Infection:

Among asymptomatic individuals, fecal excretion of norovirus is typical, especially in children. The cause of diarrhea due to norovirus infection in an asymptomatic individual can be misdiagnosed. Asymptomatic carriers resulted in consequence of transmitting the virus by fecal microbiota, and this was determined by stool samples obtained from asymptomatic donors who were not screened for norovirus infection.

Symptomatic Infection:

• Incubation Period: The incubation period is short in most individuals who develop symptoms and was estimated in the index outbreak in 1968 to be approximately 48 hours.

• Signs And Symptoms: The dominant symptoms of norovirus infections are vomiting and diarrhea for a relatively short duration. Some common symptoms are:

- Nausea.

- Vomiting.

- Abdominal pain.

- Fever or chills.

- Diarrhea.

- Headache.

- Leukocytosis.

- Thrombocytopenia.

- Dehydration.

The illness may be chronic or severe in individuals with underlying medical conditions.

• Complications: Severe disease and death at extremes of age. Infection due to GII.4 strains are associated with severe outcomes resulting in mortality than during outbreaks of non-GII.Four strains. Older age groups are at risk for fatality. Children or neonates affected with norovirus show more severe symptoms and signs than others and develop serious complications, such as necrotizing enterocolitis.

• Norovirus in Immunocompromised Individuals: The infections associated with norovirus may be prolonged and severe in some individuals and associated with remarkably persistent viral excretion.

What Are the Consequences of Norovirus Infection?

The implications of the norovirus outbreak in the United States, as reported by the Centers for Disease Control and Prevention, are as follows: every year.

• Nine hundred deaths, primarily adults aged 65 years and older.

• 109,000 hospitalizations.

• 465,000 emergency department visits, mainly children.

• Two million two hundred seventy thousand outpatients visit clinics annually, including children as a majority.

• 19 to 21 million cases were reported due to vomiting and diarrhea illnesses.

By Five Years Of Age:

• 1 in 110,000 die from norovirus infection.

• 1 in 160 gets hospitalized.

• 1 in 40 admits to the emergency department.

• 1 in 7 visits an outpatient clinic.

Norovirus infection is the leading cause of foodborne illness in the United States.

What Are the Different Outbreaks of Norovirus Infection?

Food Outbreak: Several food items are associated with norovirus infection. Food items get contaminated by mishandling through an infected person or with contaminated water.

Raspberries and oysters resulted in various national and international outbreaks.

Norovirus infections spread rapidly from person to person in community settings like schools, hospitals, daycare centers, and nursing homes. Other reported outbreaks include cruise ships due to the ideal closed setting for infection spread.

Healthcare-associated Outbreaks: Norovirus outbreaks occur due to their highly contagious and efficient transmission. Most gastroenteritis cases are attributed to norovirus infections in hospitals and long-term care facilities. Healthcare-associated norovirus outbreaks involve many patients and staff with high incidence rates. These outbreaks can be expensive due to ward closures, and the absence of staff, estimated at a1 million per 1000 hospital beds in the U.K. Transmission occurs from person to person or through contaminated surfaces. Features of healthcare norovirus outbreak:

• Low infectious dose.

• Multiple transmission routes (fecal-oral, foodborne, aerosol, waterborne).

• Widespread host susceptibility.

• Strain-specific immunity is relatively short-lived.

• Vulnerable patient populations (elderly, immunocompromised).

• Asymptomatic or prolonged shedding.

• Relative resistance to surface disinfectants.

• Stable in the environment.

How Is Norovirus Infection Transmitted?

The norovirus is found in the feces and vomiting of infected people. It is very contagious and spreads rapidly throughout healthcare facilities. The virus can be transmitted in various ways:

• Direct contact with an infected person (healthcare workers, visitors, or patients).

• Eating food or drinking water contaminated with norovirus.

• Touching objects or surfaces contaminated with norovirus, then touching the mouth or other food items.

What Is the Treatment for Norovirus Infection?

There is no specific treatment available for norovirus infection. A person can take up lots of water or fluids to stay hydrated due to vomiting and diarrhea. Dehydration can lead to hospitalization, followed by I.V. fluids. No vaccine is available for infection control or prevention.

How to Prevent Norovirus Infection?

Preventive measures include the following:

• Proper hand washing after using the toilet or bathroom and before preparing food.

• Isolation of ill people.

• Careful cleaning and disinfection of public places, toilets, etc. Disinfectants must have a virucidal effect.

• During cleaning up vomits or toilets, wearing masks to prevent infection through aerosols is advisable. Gloves are also to be used during disinfecting and cleaning.

• Handling food is avoided during gastrointestinal symptoms, and staying isolated for 48 hours after symptoms end helps prevent infection.

Conclusion:

Norovirus causes nonbacterial gastroenteritis. Gastrointestinal symptoms such as vomiting and diarrhea are the two major signs and symptoms of the infection, which can be misdiagnosed as other infections. Norovirus infections are highly contagious and spread rapidly from person to person or through contaminated food, water, or surface. Norovirus infection is associated with high death rates. Adequate preventive measures can help in infection prevention.