Introduction to Norovirus
The dreaded norovirus — the “vomiting bug” that often causes stomach flu symptoms — is climbing again in California, and doctors warn that a new subvariant could make even more people sick this season. In L.A. County, concentrations of norovirus are already on the rise in wastewater, indicating increased circulation of the disease, the local Department of Public Health told the Los Angeles Times.
Rising Norovirus Levels in California
Norovirus levels are increasing across California, and the rise is especially notable in the San Francisco Bay Area and L.A., according to the California Department of Public Health. And the rate at which norovirus tests are confirming infection is rising nationally and in the Western U.S. For the week that ended Nov. 22, the test positivity rate nationally was 11.69%, up from 8.66% two months earlier. In the West, it was even worse: 14.08%, up from 9.59%, according to the U.S. Centers for Disease Control and Prevention.
Contagious Nature of Norovirus
Norovirus is extraordinarily contagious, and is America’s leading cause of vomiting and diarrhea, according to the CDC. Outbreaks typically happen in the cooler months between November and April. Clouding the picture is the recent emergence of a new norovirus strain — GII.17. Such a development can result in 50% more norovirus illness than typical, the CDC says.
New Norovirus Strain GII.17
“If your immune system isn’t used to something that comes around, a lot of people get infected,” said Dr. Peter Chin-Hong, an infectious diseases expert at UC San Francisco. During the 2024-25 winter season, GII.17 overthrew the previous dominant norovirus strain, GII.4, that had been responsible for more than half of national norovirus outbreaks over the preceding decade. The ancestor of the GII.17 strain probably came from a subvariant that triggered an outbreak in Romania in 2021, according to CDC scientists.
Impact of Norovirus
Norovirus can cause substantial disruptions — as many parents know all too well. An elementary school in Massachusetts was forced to cancel all classes on Thursday and Friday because of the “high volume of stomach illness cases,” which was suspected to be driven by norovirus. More than 130 students at Roberts Elementary School in Medford, Mass., were absent Wednesday, and administrators said there probably wouldn’t be a “reasonable number of students and staff” to resume classes Friday.
Prevention and Treatment
People usually develop symptoms 12 to 48 hours after they’re exposed to the virus. Hand sanitizer does not work well against norovirus — meaning that proper handwashing is vital, experts say. People should lather their hands with soap and scrub for at least 20 seconds, including the back of their hands, between their fingers and under their nails, before rinsing and drying, the CDC says. One helpful way to keep track of time is to hum the “Happy Birthday” song from beginning to end twice, the CDC says.
High-Risk Groups
Children under the age of 5 and adults 85 and older are most likely to need to visit an emergency room or clinic because of norovirus, and should not hesitate to seek care, experts say. “Everyone’s at risk, but the people who you worry about, the ones that we see in the hospital, are the very young and very old,” Chin-Hong said. Those at highest risk are babies, because it doesn’t take much to cause potentially serious problems.
Conclusion
Norovirus is a highly contagious and potentially serious illness that can cause significant disruptions to daily life. The emergence of a new strain, GII.17, has the potential to make even more people sick this season. It is essential to take preventive measures, such as proper handwashing and cleaning of surfaces, to reduce the risk of infection. If symptoms persist or worsen, it is crucial to seek medical attention, especially for high-risk groups such as young children and older adults.
FAQs
Q: What is norovirus?
A: Norovirus is a highly contagious virus that causes vomiting and diarrhea, and is the leading cause of stomach flu symptoms in the United States.
Q: How is norovirus spread?
A: Norovirus is spread through contaminated food and water, and by touching contaminated surfaces and then placing fingers in the mouth.
Q: What are the symptoms of norovirus?
A: Symptoms of norovirus include vomiting, diarrhea, stomach cramps, and fever.
Q: Who is at highest risk for norovirus?
A: Children under the age of 5 and adults 85 and older are at highest risk for norovirus.
Q: How can I prevent norovirus?
A: Preventive measures include proper handwashing, cleaning of surfaces, and avoiding close contact with individuals who are infected.
Q: What should I do if I think I have norovirus?
A: If symptoms persist or worsen, it is essential to seek medical attention, especially for high-risk groups such as young children and older adults.
