Key Facts

Norovirus causes gastrointestinal symptoms such as vomiting, diarrhea, and abdominal pain.

People of all ages can become infected and develop symptoms.

Proper handwashing and maintaining basic hygiene practices significantly reduce the risk of norovirus infection and transmission.

What Is Norovirus?

Norovirus is a highly contagious virus that causes acute gastroenteritis, with symptoms of vomiting and diarrhea. The virus can survive for weeks on contaminated surfaces and objects (work surfaces, door handles, phones, furniture), enabling rapid and easy person-to-person transmission. As a result, it can spread quickly in closed settings such as schools, kindergartens, hospitals, nursing homes, restaurants, correctional facilities, and camps.

It is often referred to as the “stomach virus” or “stomach flu,” but it is not related to influenza. Most infected individuals recover within 1–3 days, but they may continue to spread the virus for several days after symptoms resolve.

Infections can occur throughout the year, but incidence is highest from November to April.

How Is Norovirus Transmitted?

Norovirus is shed in the feces and vomit of infected individuals. Vomiting can generate aerosols that contaminate the environment. The fecal–oral route of transmission is dominant, and transmission via contaminated, unwashed hands is very common.

A person is contagious from the onset of symptoms until several days after symptoms subside, and viral shedding may last for two weeks or longer.

There are many types and genotypes of norovirus, which is why infection can occur multiple times during a person’s lifetime. Infection with one type does not protect against infection with another. Immunity is type-specific and its duration is not clearly established, which explains why people of any age can be reinfected during outbreaks.

Routes of Transmission

Norovirus is extremely contagious and spreads easily and rapidly through:

·         Direct contact with an infected person (caregiving, sharing food/utensils, consuming food prepared by an infected person, diaper changing);

·         Consumption of contaminated food or beverages;

·         Consumption of norovirus-contaminated water, including pool water;

·         Contact with contaminated surfaces and transferring the virus to the mouth (especially in young children);

·         Use of shared toilets with individuals already infected with norovirus;

·         Improper cleaning of vomit or feces from infected persons without appropriate personal protective equipment (gloves, mask);

·         Prolonged viral shedding — a person may transmit the virus for up to two weeks or longer after recovery;

The virus can survive on surfaces and objects for weeks.

Who Is at Risk?

Anyone can become infected with norovirus.

Higher risk of severe disease is seen in:

·         Children under 5 years of age

·         Older adults

·         Immunocompromised individuals

Clinical Manifestations

The incubation period (time from exposure to onset of symptoms) is usually 12–48 hours. Symptoms typically last 1–3 days.

Most common symptoms:

·         Acute vomiting

·         Diarrhea

·         Nausea

·         Abdominal pain and cramps

·         Additional symptoms:

·         Low-grade fever

·         Headache

·         Muscle aches

Symptoms are similar in adults and children; however, diarrhea may predominate in adults, while children may experience more severe vomiting.

Dehydration

Norovirus infection can cause multiple episodes of vomiting and diarrhea throughout the day, which may lead to dehydration, especially in:

·         Young children

·         Older adults

·         People with chronic illnesses

Signs of dehydration include:

·         Reduced urination

·         Dark-colored urine

·         Dry mouth and throat

·         Dizziness when standing

·         In children: crying without tears or with few tears, drowsiness, or irritability

Testing and Diagnosis

Diagnosis is made through laboratory testing by detecting the virus in stool samples (most commonly using RT-PCR) and by detecting viral antigens. During outbreaks, laboratory confirmation is crucial for identifying the source and implementing control measures.

The Department of Virology at the Institute of Public Health has diagnostic tests available for norovirus based on clinical (with referral from a general practitioner or infectious disease specialist) and epidemiological indications. Testing is available to citizens during the first and second shifts on all working days.

Treatment

There is no specific antiviral therapy, and norovirus does not respond to antibiotics (as it is a virus, not a bacterium). Treatment is symptomatic and is based on oral (fluid intake by mouth) or intravenous rehydration.

Adequate fluid intake is the most important measure.

Oral rehydration solutions are the most appropriate.

Most patients recover within 1–3 days.

When Is Medical Help Needed?

Severe dehydration may require hospital treatment with intravenous rehydration. Medical help should be sought if signs of dehydration are observed.

Preventive Measures

Although norovirus is highly contagious, infection can be prevented through the following measures:

·         Maintaining basic hygiene practices significantly reduces the risk of infection and transmission.

·         Frequent and thorough handwashing with soap and water (≥20 seconds), especially after using the toilet, changing diapers, and before handling food.

·         Thorough heat treatment of food and washing fruits and vegetables.

·         Avoiding food handling and caregiving for others while contagious.

·         Home treatment and absence from work/school during symptoms. People working in healthcare and food services should avoid work for at least 48 hours after symptoms resolve.

·         Cleaning and disinfecting contaminated surfaces (noting that alcohol-based disinfectants are less effective against norovirus).

·         Washing clothes and bed linen at temperatures above 60°C.

·         Disinfecting contaminated surfaces with solutions containing sodium hypochlorite.

·         Staying at home for at least 48 hours after symptoms resolve.

·         When traveling abroad, consuming cooked food, avoiding street food vendors, and drinking bottled water.

·         Frequent ventilation, surface cleaning, and disinfection.