Human norovirus is a highly contagious virus and the most common cause of gastroenteritis, an inflammation of the stomach and intestines. Often called the “stomach flu,” it is not related to the influenza virus and is a leading cause of vomiting and diarrhea. The virus is named after Norwalk, Ohio, where the first recognized outbreak occurred in 1968.
Noroviruses are a genetically diverse group of viruses. This diversity, along with a tendency for mutation, contributes to its widespread impact. Because infection with one type of norovirus may not protect against others, people can experience repeat infections throughout their lives.
Identifying Norovirus Infection
The signs of a norovirus infection appear suddenly, between 12 and 48 hours after exposure. The most common symptoms include:
- Nausea
- Forceful vomiting
- Watery and non-bloody diarrhea
- Stomach pain
Individuals may also experience a low-grade fever, headache, and general body aches.
Although the illness can be intense, it is self-limiting, and most people recover within one to three days without medical treatment. An individual can continue to spread the virus for several days after feeling better. In some cases, the virus can be shed in stool for weeks.
How Norovirus Spreads
Norovirus is extremely contagious, requiring only a small number of viral particles to cause infection. A primary mode of transmission is direct contact with an infected person, such as through providing care or shaking hands.
The virus also spreads when people consume contaminated food or water. Foods like leafy greens, fresh fruits, and shellfish are common sources of outbreaks, especially if handled by an infected person.
Contaminated surfaces are another source of transmission, as the virus can survive for days or weeks on objects. A person can become infected by touching a contaminated surface and then their mouth. Additionally, aerosolized particles from vomit can travel through the air, settle on surfaces, or be inhaled.
Preventing Norovirus Contamination
Proper hand hygiene is a primary defense against norovirus. Frequent handwashing with soap and water for at least 20 seconds is recommended, particularly after using the bathroom and before preparing or eating food. Alcohol-based hand sanitizers can offer some benefit but are not as effective as soap and water at removing the virus.
To prevent the virus from spreading, immediately disinfect contaminated areas. After an episode of vomiting or diarrhea, clean surfaces using a chlorine bleach solution. A recommended concentration is 5 to 25 tablespoons of household bleach per gallon of water.
Safe food handling practices reduce the risk of transmission. Wash fruits and vegetables thoroughly and cook shellfish to a proper internal temperature. People sick with norovirus should not prepare food for others while symptomatic and for at least two days after recovery. Handle contaminated clothing carefully and wash with hot water.
Managing Norovirus and Potential Complications
There is no specific medicine for norovirus, and antibiotics are ineffective as it is a virus. Treatment focuses on supportive care to manage symptoms, with the primary goal being to stay hydrated. Drink plenty of fluids to replace those lost through vomiting and diarrhea.
Oral rehydration solutions, sports drinks, and water are good choices for maintaining hydration. Avoid sugary drinks and alcohol, as they can worsen diarrhea. Getting adequate rest also helps the body recover.
The most common complication of norovirus is dehydration. Young children, older adults, and people with other health conditions are at the greatest risk. Signs of dehydration include decreased urination, a dry mouth and throat, and dizziness when standing. Seek medical attention if symptoms of dehydration appear or if the illness lasts more than a few days.