Norovirus is a highly contagious infection also known as Norwalk virus. It is a common cause of vomiting and diarrhea each winter and is often referred to as ‘winter vomiting disease’ or ‘stomach flu’ (although it is not caused by the influenza virus). Norovirus infections have been linked to outbreaks of vomiting and/or diarrhea in child care centres and schools, long-term care and retirement homes, cruise ships, camps, restaurants, households and other places where people gather.
Norovirus spreads easily, and commonly within the household of a person sick with the virus.
Norovirus is found in the stool and sometimes in the vomit of a person sick with the virus. People can become infected with the virus in several ways:
Those infected with Norovirus usually spread it once they feel ill and for up to two days after the symptoms (usually diarrhea) stop but can continue to spread the virus for up to two weeks after their symptoms stop.
People infected with Norovirus usually experience sudden onset of nausea, vomiting, stomach cramps and watery diarrhea that lasts about one to three days. Other symptoms may include fever, headache, muscle aches and malaise.
Symptoms usually appear within ten hours but can develop up to two days after exposure to the virus. Infected individuals usually recover in two to three days without serious or long-term health effects.
Severe illness or hospitalization is uncommon. Dehydration is the most common complication, especially among young children and the elderly.
Seek medical attention or call Health Connect Ontario (8-1-1) to talk to a registered nurse if you have high fever, bloody diarrhea or illness lasting longer than 72 hours.
Doctors generally diagnose Norovirus infection based on symptoms including the sudden onset, the short duration (usually one to three days) and the quick resolution of the infection. However, a stool sample may be collected by your doctor in certain circumstances.
People sometimes call Norovirus infection the “stomach flu.” However, influenza (the flu) is a respiratory (lung) illness with symptoms of cough, sore throat and fever. Getting your flu vaccine each fall/winter, while important for protection against the flu, will not protect you against Norovirus infection.
There currently is no vaccine available in Canada to prevent Norovirus infection.
Most people will recover from a Norovirus infection with no complications. The symptoms of Norovirus infection may be more severe for infants, young children, the elderly and those with weak immune systems. Dehydration can be more serious for these individuals and they should seek medical attention if this becomes severe.
There is no specific treatment for Norovirus infection. Antibiotics are not useful because the illness is caused by a virus, not a bacterium. Individuals who are sick with Norovirus should drink plenty of fluids to prevent dehydration.
Norovirus infections are typically not reportable to public health. However, outbreaks of enteric illness that may be caused by norovirus that occur in institutions (such as hospitals, long term care homes or retirement homes), schools or child care centres, or other community settings are reportable. Public health plays a role in the follow up of such outbreaks to investigate cause, provide appropriate follow up to those who are affected and/or sick and ensure control measures are in place to prevent the spread of infection.