The norovirus, often referred to as the “vomiting bug,” is rising in prevalence again in California, prompting concerns from health officials about a new subvariant that could impact even more people this winter. The L.A. County Department of Public Health has detected increased concentrations of norovirus in wastewater, indicating a surge in the virus’s circulation.
Across the state, the California Department of Public Health reports an uptick in norovirus levels, particularly in the San Francisco Bay Area and Los Angeles. Nationally, the test positivity rate for norovirus infections has increased significantly from 8.66% to 11.69% within two months, with the Western U.S. experiencing an even steeper rise from 9.59% to 14.08%, according to the U.S. Centers for Disease Control and Prevention (CDC).
The CDC highlights that norovirus outbreaks are most common during the cooler months, typically from November to April, when the virus is extraordinarily contagious and remains a leading cause of vomiting and diarrhea in the United States. The emergence of a new strain, known as GII.17, has raised alarms as it has been linked to a surge in norovirus cases, potentially leading to a 50% increase in illness.
Dr. Peter Chin-Hong, an infectious disease expert at UC San Francisco, explains that if someone’s immune system is unfamiliar with this strain, it can facilitate widespread infection. This new strain gained prominence after dethroning the previously dominant GII.4 strain that has been responsible for many outbreaks over the last decade.
Despite this worrying trend, not all regions in California are currently experiencing severe norovirus activity. So far this year, 32 lab-confirmed outbreaks have been reported statewide, compared to 69 the previous year. Meanwhile, some prominent institutions, such as UCLA, have not observed significant increases in testing or positivity rates.
Norovirus outbreaks can disrupt daily life significantly, as seen in a recent incident at Roberts Elementary School in Massachusetts, where over 130 students were absent due to suspected norovirus infection, and classes were canceled for a thorough cleaning.
The CDC estimates that norovirus results in approximately 2.27 million outpatient visits annually, with young children and older adults facing the highest risk of severe illness. Symptoms typically manifest within 12 to 48 hours of exposure, and those affected should seek medical advice if experiencing severe symptoms, particularly dehydration.
To combat the spread of norovirus, health officials emphasize the importance of proper handwashing, as hand sanitizer is ineffective against the virus. People are urged to scrub their hands with soap for at least 20 seconds, ensuring all parts of the hands are thoroughly cleaned. Environmental cleaning, especially when living with someone infected, is also critical in preventing transmission.
The CDC continues to monitor norovirus trends and urges the public to remain vigilant, especially during the peak outbreak season. As holiday gatherings and travel approach, awareness and hygiene become even more essential to curtail the impact of this contagious virus.