CDC: 2024-2025 seasonal norovirus outbreaks up from previous years

CDC: 2024-2025 seasonal norovirus outbreaks up from previous years | Image Credit: © Vitalii Vodolazskyi - © Vitalii Vodolazskyi - stock.adobe.com.

From August 1, 2024, through December 11, 2024, there were 495 norovirus outbreaks reported by the Norovirus Sentinel Testing and Tracking(NoroSTAT)-participating states, according to statistics from the CDC's current norovirus season webpage.¹

The federal agency noted that the total number of outbreaks in the current 2024-2025 seasonal year is above the range reported for the same time periods during the 2012-2020 and 2021-2024 seasonal years.¹

The leading cause of vomiting, diarrhea and foodborne illnesses in the United States, norovirus is a very contagious virus sometimes referred to as the "stomach flu" or "stomach bug," though norovirus is not related to the flu. The virus causes acute gastroenteritis, an inflammation of the stomach or intestines.^1,2

According to the CDC, most people with norovirus illness get better within 1-3 days, but can spread the virus for a few days after recovery.²

The federal agency defines a norovirus outbreak as the occurrence of 2 or more similar illnesses resulting from a common exposure that is either suspected or laboratory-confirmed to be caused by norovirus.³

NoroSTAT is a network of state health departments that work with CDC to provide near real-time reporting and monitoring of norovirus outbreak activity.⁴

According to CaliciNet—a network of public health laboratories—the dominant strain of norovirus is currently GII.17, which made up 69.7% of the genotype distribution among norovirus outbreaks from September 1, 2024 to December 31, 2024.^5,6

"It is too early to tell if this strain is associated with more severe norovirus disease but likely lower population immunity is the reason for the early surge of an otherwise seasonal increase of this virus," said Jan Vinjé, head of the CDC's CaliciNet system, according to a CBS News online article, posted January 8, 2024.⁵

According to the CDC, people of all ages can get infected and sick with norovirus, with symptoms typically developing 12 to 48 hours after being exposed to the virus. The most common symptoms are diarrhea, vomiting, nausea, and stomach pain, though fever, headache, and body aches are other symptoms often reported.²

Children aged younger then 5 years are more likely to develop severe infections, as are older adults and those with weakened immune systems.²

The federal agency recommends simple steps to protect from infection, including²:

• Wash your hands well and often.
• Cook shellfish thoroughly and wash fruits and vegetables.
• Clean and disinfect contaminated surfaces.
• Wash laundry in hot water.

Additionally, the CDC recommends watching for signs of dehydration in children who have norovirus. Those who have been infected should drink a lot of liquids to replace fluid lost from diarrhea and vomiting.²

References:

1. NoroSTAT data. CDC. Accessed January 9, 2024. https://www.cdc.gov/norovirus/php/reporting/norostat-data.html

2. About norovirus. CDC. Accessed January 9, 2024. https://www.cdc.gov/norovirus/about/index.html

3. Norovirus outbreaks. CDC. Accessed January 9, 2024. https://www.cdc.gov/norovirus/outbreak-basics/index.html

4. NoroSTAT Surveillance Network. CDC. Accessed January 9, 2024. https://www.cdc.gov/norovirus/php/reporting/norostat.html

5. Tin A. It feels like everyone has a stomach bug. A new norovirus strain might be to blame, CDC data suggests. CBS News. January 8, 2024. Accessed January 9, 2024. https://www.cbsnews.com/news/new-norovirus-strain-us-wave-stomach-bug/

6. CaliciNet Data. CDC. Accessed January 9, 2024. https://www.cdc.gov/norovirus/php/reporting/calicinet-data.html