Cases of norovirus and whooping cough are rising across the U.S., prompting health officials to issue warnings as the country enters peak cold and flu season.
Here are seven things to know:
- Norovirus outbreaks have reached the highest levels for this time of year for the first time in a decade, with the CDC reporting 91 outbreaks during the week of Dec. 5, 2024, marking a 22-outbreak increase from the previous week. Data from the CDC's NoroSTAT table shows the number of outbreaks has been consistently high, with the latest surge exceeding 65 outbreaks in late November and early December.
- Norovirus is highly contagious and causes symptoms of vomiting, diarrhea, fever and body aches, which can lead to dehydration, especially in young children and older adults, The Washington Post reported Dec. 30. The virus spreads through direct contact with infected individuals or contaminated food and water. The incubation period ranges from 12 to 48 hours, meaning symptoms can appear several hours after exposure and infected individuals remain contagious for up to two weeks, even after symptoms subside.
- Some hospitals are reporting a significant uptick in norovirus cases amid the outbreaks. For example, Rancho, Mirage, Calif.-based Eisenhower Health has seen a steep jump in norovirus patients this month, alongside flu cases. Annually, there are around 109,000 hospitalizations and 465,000 emergency department visits for norovirus in the U.S., with most patients including young children, according to the Post.
- The seasonal increase in norovirus cases is tied to colder months, when people gather indoors more frequently, especially for the holidays. Experts believe the pandemic-era reduction in outbreaks and heightened hygiene practices may have left many with lower immunity.
- Whooping cough cases have reached the highest annual total in a decade, according to a Dec. 23 NBC News report. By mid-December 2024, over 32,000 cases had been reported, compared to just 5,100 cases at the same time in 2023. Experts attribute the increase to a combination of factors, including waning vaccine protection, lower vaccination rates and improved testing, which has allowed for better detection. Infants are particularly vulnerable to complications from the illness.
- To prevent the spread of norovirus, experts recommend frequent handwashing, disinfecting contaminated surfaces and staying home for at least 48 hours after symptoms end. For whooping cough, the CDC stresses the importance of vaccination, recommending the DTaP vaccine for infants and the Tdap booster for older children and adults.
- Meanwhile, respiratory virus levels are increasing in many parts of the country. Twenty four states reported high virus levels for the week ending Dec. 21, according to the latest CDC data. Emergency department visits for COVID-19, flu and respiratory syncytial virus are all on the rise, with flu accounting for the highest percentage.