Norovirus is experiencing a significant surge across the U.S., with case numbers higher than they’ve been at this time in over a decade, according to the U.S. Centers for Disease Control and Prevention (CDC). The highly contagious virus, which causes vomiting and diarrhea, has prompted concerns among health experts, especially as researchers work on developing a vaccine using mRNA technology, similar to that used for COVID-19 vaccines.
What’s Behind the Current Outbreak?
Norovirus, commonly known as the stomach flu, has long been a leading cause of gastroenteritis, or inflammation of the intestinal tract. Dr. Edmund Milder, a pediatric infectious disease specialist at UC San Diego Health, explains that the virus has been circulating for years, with nearly 50 different subtypes. For the last decade, the GII.4 strain was dominant, but a shift occurred last year when GII.17 became the primary variant, which could partially explain the recent uptick in cases. People who were exposed to the older strains may not have immunity to this new version, making them more susceptible.
Symptoms and Risks
Norovirus causes intense gastrointestinal symptoms, including vomiting, diarrhea, and dehydration. While these symptoms are usually short-lived and don’t require medical treatment, older adults and infants can experience more severe illness. According to the CDC, about 100,000 people are hospitalized each year in the U.S. due to the virus, and nearly 1,000 people, mainly elderly or very young individuals, die from complications such as dehydration.
Challenges in Preventing Norovirus
What sets norovirus apart from other viruses is its contagiousness. As few as 10 particles of the virus can trigger illness, and its hardy structure allows it to survive on surfaces like countertops and doorknobs for days. Hand sanitizers are ineffective against it, and only thorough handwashing with soap and water for at least 20 seconds can help reduce the spread. Additionally, high heat and cold temperatures do not destroy the virus, making it harder to manage. To disinfect surfaces, experts recommend using a diluted bleach solution.
Progress Toward a Vaccine
There is currently no antiviral treatment or vaccine for norovirus, but Moderna is working on the first potential vaccine, using mRNA technology. The vaccine aims to protect against multiple strains of the virus, with ongoing phase 3 trials enrolling 25,000 participants worldwide. Dr. Doran Fink of Moderna explains that the vaccine includes three different norovirus types, providing hope for broader protection against severe disease.
While the vaccine is not designed to prevent infection outright, it may reduce the severity of symptoms, particularly for vulnerable groups like the elderly and children. Moderna’s trials are expected to wrap up in spring, but it may take longer to evaluate the vaccine’s effectiveness in the real world.
Preventive Measures
Until a vaccine becomes widely available, the best defense against norovirus remains practicing good hygiene. Frequent handwashing, avoiding contact with sick individuals, and staying home if you are ill are key strategies to reduce transmission. Even after symptoms subside, individuals can continue shedding the virus, so it is important to remain cautious in the days following recovery.
