A new strain of norovirus is responsible for most of the recent outbreaks across the country, potentially explaining why there’s been a sharp increase in infections recently. Known as GII.17[P17], this strain caused nearly 70% of all norovirus outbreaks from September to December 2024, based on CDC data.
The CDC noted that there were 91 norovirus outbreaks reported by state health departments in the week ending December 5, which is the highest recent record. On cruise ships, norovirus cases also peaked, with at least six outbreaks reported on different vessels in December.
Norovirus, especially the GII.17 strain, seems to be widespread right now, as mentioned by Dr. Jan Vinjé from the CDC. While it’s uncertain if this strain directly causes more severe illness, the early surge in cases might be due to lower population immunity during what is usually a seasonal increase in this virus.
Here’s what to know about this norovirus strain: while it’s being called new, it actually emerged in 2014-15 and spread worldwide. Dr. Amesh A. Adalja from the Johns Hopkins Center for Health Security pointed out that, although it started dominating outbreaks only in the past year, it was responsible for 109 outbreaks from September 2023 to August 2024. Previously, the GII.4 strain led outbreaks since 2012 but accounted for only 84 within the same period. So far, from September to December 2024, GII.17 was involved in 39 outbreaks compared to just four for GII.14.
Since GII.17 is relatively new, people might not have developed enough immunity, making them more susceptible to infection. Dr. Thomas Russo from the University at Buffalo agrees, highlighting that previous immunity might not be effective against this variant, thus potentially causing more infections. However, more research is necessary to definitively link GII.17 to the increase in cases.
There are numerous norovirus strains, which means people can get infected multiple times throughout their lives. Immunity developed from one strain might not protect against others, similar to how COVID variants work, as noted by Dr. Russo.
Regarding symptoms, there’s no significant difference in how GII.17 presents. It typically causes the usual norovirus symptoms like diarrhea, vomiting, nausea, stomach pain, fever, headache, and body aches. Preventing and treating norovirus hasn’t changed with this strain. Good hand-washing habits with soap and water are crucial because hand sanitizers aren’t effective against norovirus. Washing clothes in hot water can help, and avoiding those who are obviously ill is wise.
There is no specific treatment for norovirus. Staying hydrated is essential, and taking small sips of liquids can help keep them down. Over-the-counter medications like acetaminophen can alleviate fever and body aches. Dr. Russo emphasizes reducing norovirus risk, noting that dealing with it is quite unpleasant, as it typically means 24 to 48 hours of discomfort.
