Norovirus cases are higher than usual for this time of year. Norovirus is highly contagious and causes vomiting and diarrhea that lasts 2-3 days. A small amount of the virus is enough to make someone sick. It is spread through contaminated food and surfaces. Public health experts are still learning about the cause of the increase. Alcohol-based hand sanitizers may not kill the virus, so the best prevention is washing hands often with soap and water.

A CDC norovirus monitoring program in 14 states shows higher than usual norovirus levels for this time of year. During the first week of the New Year’s holiday, nearly 28% of norovirus tests returned positive, more than double the 13.52% peak positivity rate seen in March 2024.

A CDC norovirus monitoring program in 14 states shows higher than usual norovirus levels for this time of year. During the first week of January, about 28% of tests were positive for norovirus, which was double the 14% test positivity rate seen in March 2024.

Norovirus is highly contagious, and human immunity to norovirus doesn’t last very long – 6 months to 2 years -- after someone gets sick. The virus can have genetic variations every year which makes it more likely people who had it before could get sick again.  For these reasons, it is not unusual for norovirus cases to be higher than usual in some years.

People can be contagious with norovirus before they get sick or after they start to feel better. It is important to continue to limit contact with others at least 2 days after symptoms stop to avoid spreading the virus.

People can also get the virus from contaminated food like oysters, shellfish, and leafy greens. To help prevent getting norovirus from contaminated food, cook shellfish and oysters to a temperature of 145 degrees, wash fruits and vegetables, and disinfect surfaces that unwashed produce or raw shellfish have touched.

There is not enough data to tell if the norovirus illnesses are more severe this year, and more data is needed to confirm if a different strain of norovirus is causing the increase in cases.