Is the New Norovirus Strain Behind a Rise in Infections in the US? Key Symptoms to Watch For

Norovirus cases have surged recently, joining the usual seasonal culprits—flu, RSV, and COVID—leading to increased infections. Health officials are concerned about this spike, which has been linked to a new strain, GII.17[P17]. According to the Centers for Disease Control and Prevention (CDC), this strain was responsible for nearly 70% of all norovirus outbreaks from September 2024 to December 2024. The CDC reported 91 outbreaks for the week ending in December.

Is the New Strain More Contagious?

Although the rise in norovirus cases is attributed to the GII.17 strain, it’s still unclear if this strain is specifically more infectious. “It’s too early to tell if this strain causes more severe illness,” said Jan Vinjé, PhD, Head of the CDC’s National Calicivirus Laboratory. He added that the surge is likely due to lower population immunity, resulting in an early uptick in an otherwise seasonal virus.

About the GII.17 Strain

The GII.17 strain first emerged around 2014-2015 and spread globally but has only recently gained attention due to the rise in cases from September 2023 to August 2024. This strain caused 109 outbreaks, while the previously dominant GII.4 strain, which had been prevalent since 2012, led to 84 outbreaks. The increase in GII.17 cases may be due to a lack of immunity, and since there are multiple strains of norovirus, infection with one does not guarantee protection against others.

Symptoms of the GII.17 Strain

While symptoms are generally consistent across norovirus strains, they include diarrhea, vomiting, nausea, stomach pain, fever, headache, and body aches. Norovirus infections can be intense and, although they typically last 1-3 days, they can lead to severe dehydration. Experts recommend drinking small sips of water and eating light foods like soup during recovery.

To prevent infection, washing hands with soap and hot water is effective, while hand sanitizers are less reliable.