A new and highly contagious wave of norovirus, often dubbed the 'winter vomiting bug,' is sweeping across the United States as the year draws to a close. This surge is being propelled by a fast-spreading variant, adding to a concerning mix of rising respiratory illnesses nationwide, including flu, whooping cough, measles, and COVID-19.
Rapid Spread and Dominant New Variant
Recent data indicates a sharp national increase in norovirus cases. According to the Centers for Disease Control and Prevention (CDC), the national positivity rate hit 9.9% for the week ending December 9, climbing further to 12.11% for the week ending December 13. This uptick is largely attributed to the emergence of a new subvariant, GII.17.
CDC statistics reveal a dramatic shift in variant dominance. Outbreaks caused by GII.17 skyrocketed from just 7.5% in the 2022–23 season to a staggering 75.4% in the 2024–25 season. Concurrently, outbreaks linked to the previously dominant GII.4 variant plummeted from nearly 49% to 10.7%.
Geographically, the surge is widespread. California has seen a significant spike, with the San Francisco and Los Angeles areas reporting massive climbs. States including Michigan, New Jersey, North Carolina, Texas, Oklahoma, Colorado, Alabama, Montana, and Wyoming have all reported rising case numbers, as per Epic Research data.
Health Impact and Co-Circulating Threats
Norovirus is a potent stomach bug that causes inflammation of the stomach and intestines, leading to severe vomiting and diarrhoea, earning it the moniker 'extreme vomiting disease.' It infects an estimated 20 million people in the US each year. While most recover, the illness can be severe, requiring medical attention or even hospitalization for vulnerable groups like the immunocompromised, the elderly, and young children.
This norovirus wave arrives amidst a crowded field of seasonal illnesses. COVID-19 cases are surging nationwide, with 31 states reporting growing infections, many driven by the XFG Stratus variant. Health experts are also monitoring a new flu outbreak in Europe caused by a version of H3N2, highlighting a complex public health landscape.
Symptoms, Treatment, and Prevention
Symptoms of norovirus typically appear 12 to 48 hours after exposure and include:
- Diarrhoea
- Vomiting
- Nausea
- Stomach pain
- Dehydration
Fever or body aches are less common. There is no specific antiviral treatment for norovirus. The Cleveland Clinic notes that symptoms generally resolve within one to three days.
Health officials recommend the following for management and prevention:
- Drink plenty of liquids and electrolytes to prevent dehydration.
- Eat bland foods as you recover.
- Wash hands thoroughly with soap and water, as hand sanitiser is ineffective against norovirus.
- Disinfect contaminated surfaces.
- Avoid preparing food for others for several days after symptoms subside to limit spread.
The concurrent rise of multiple infectious diseases underscores the importance of vigilance and basic hygiene practices, especially during the holiday travel and gathering season.
