Norovirus cases rise ahead of holiday season, CDC data shows

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Norovirus cases have been on the rise in the United States in recent weeks, as reported by the Centers for Disease Control and Prevention (CDC). Data from the CDC shows that nearly 14% of tests for norovirus came back positive during the week ending on Nov. 15, with over 2,700 tests conducted, resulting in approximately 380 diagnosed cases.

This surge in cases represents a significant increase compared to three months ago, when the test positivity rate was at its lowest. In August, only 6.53% of tests conducted in the U.S. came back positive. While test positivity rates may fluctuate depending on the number of tests conducted, they provide valuable insights into the prevalence of diseases circulating in a given period.

Norovirus, also known as the stomach bug or stomach flu, is the primary cause of vomiting and diarrhea in the United States. It is also the leading cause of foodborne illness, according to the CDC. This highly contagious virus can lead to symptoms such as nausea, abdominal pain, vomiting, and diarrhea, typically lasting for one to three days.

The CDC reports that millions of people are affected by norovirus each year, with approximately 2,500 outbreaks reported annually in the U.S. This illness results in over 100,000 hospitalizations and around 900 deaths per year, with adults aged 65 and older at the highest risk of mortality. Young children and individuals with weakened immune systems are also more susceptible to severe illness or death.

Norovirus outbreaks are most common between November and April, with a significant surge recorded in January 2025. Recent instances of potential outbreaks include a Michigan middle school closing for deep cleaning after numerous students reported feeling unwell, as well as nearly 100 cruise ship passengers falling ill with norovirus in October.

Preventative measures recommended by the CDC to curb the spread of norovirus include frequent handwashing, safe handling and preparation of food, and regular cleaning of surfaces. It is important to continue these precautions for at least two days after symptoms subside, as the virus remains contagious even after recovery.

In conclusion, the recent increase in norovirus cases serves as a reminder of the importance of practicing good hygiene and sanitation to prevent the spread of this highly contagious illness. By following the CDC’s guidelines and remaining vigilant, we can help reduce the impact of norovirus outbreaks in our communities.

This article has been edited by Sarah Lynch Baldwin.