Is rotavirus spreading in LA County? Is it different from norovirus?
Is rotavirus spreading in LA County? Is it different from norovirus?
Paris Barraza and Daniella Segura, USA TODAYFri, April 17, 2026 at 11:38 PM UTC
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A highly contagious virus that health officials say is more common in infants and young children was recently detected at high concentrations in parts of California.
Rotavirus causes diarrhea, vomiting and — particularly dangerous for young children and infants — a loss of appetite and dehydration, according to the Centers for Disease Control and Prevention.
The Los Angeles County Department of Public Health said it has observed an increase in rotavirus concentrations in wastewater in recent weeks, which suggests “increased community transmission.”
Despite that, concentrations of rotavirus overall are far smaller than what they observed at its peak last June, the department said in an email to the USA TODAY Network.
According to the department, it’s challenging to estimate the prevalence of rotavirus in the county. Also key: The virus circulates in the community year-round, the department said.
Prior to a rotavirus vaccine becoming available in 2006, the disease resulted in hundreds of thousands of hospital and emergency room visits annually, according to the California Department of Public Health. With the advent of a vaccine, however, “the number of children getting sick with rotavirus fell dramatically.”
The virus, though, remains highly contagious, health officials said, adding that “low vaccination rates can lead to outbreaks.”
In recent weeks, the percent of positive rotavirus tests at the national level has increased, according to data from the National Respiratory and Enteric Virus Surveillance System.
Earlier April, San Francisco Bay Area cities like San Jose and Palo Alto were among several areas where high concentrations of rotavirus was detected, according to the Desert Sun, which is part of the USA TODAY Network.
However, the symptoms of rotavirus may look similar to something else — the “very contagious” norovirus sometimes referred to as the stomach flu, said the CDC.
Rotavirus vs. norovirus: What’s the difference?
The L.A. County public health department said that both the norovirus and the rotavirus “present with very similar symptoms” such as vomiting, diarrhea and fever.
“Clinically it may be difficult to tell the difference between the two viruses since the symptoms overlap,” the department said. “However, rotavirus tends to have a disproportionate effect on young children.”
According to the CDC, while rotavirus is most common in infants and young children, older children and adults can get sick from it as well.
Is norovirus spreading in LA County?
Like rotavirus, norovirus circulates in the community year-round, according to the department.
“In 2026, wastewater concentrations of norovirus peaked around March and are declining in recent measurements,” the department said.
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What are rotavirus symptoms?
People infected by rotavirus will typically start to show symptoms two days after being exposed, the CDC said.
The CDC said the most common symptoms of rotavirus include:
Severe watery diarrhea
Vomiting
Fever
Stomach pain
Vomiting and watery diarrhea can last between three to eight days, according to the CDC.
One major symptom to monitor, especially with children, is dehydration, according to Dr. Jeffrey D. Klausner, a professor of medicine and public health at USC Keck School of Medicine.
“Signs of dehydration could be tiredness,” Klausner said. “It could be excessive sleeping, could be just not playing or interacting.”
Other signs of dehydration according to the CDC are:
Decreased urination
Dry mouth and throat
Feeling dizzy when standing up
Crying with few or no tears
Unusual sleepiness or fussiness
If there are any signs of dehydration in children, it’s reason enough to bring them to a pediatrician’s office, urgent care, or even emergency room if necessary, according to Klausner.
What to know about norovirus symptoms
Vomiting, diarrhea, nausea and stomach cramps are the common symptoms someone will have, according to the CDPH.
Other symptoms can include fever, headache and body aches.
How does rotavirus spread?
People infected with rotavirus pass the virus in their stool, then the virus can enter the environment and infect others, according to the CDC.
You can get infected with the virus if it enters your mouth by:
Putting your unwashed hands that are contaminated into your mouth
Touching contaminated objects or surfaces and then putting your fingers in your mouth
Eating contaminated food
It is common for the virus to spread in childcare settings, “where it's just passed from child to child through sharing toys, touching each other or contaminated surfaces,” Klausner said.
How does norovirus spread?
When a person with norovirus vomits, the virus can spray into the air and land on nearby surfaces and objects, said the CDPH. It can also spread if their feces get onto surfaces.
Among the many ways you can get norovirus include by touching something contaminated with norovirus and then touching your mouth or your food, by sharing the toilet or bathroom with someone who is sick with norovirus and by sharing food with someone who is sick norovirus, said the CDPH.
Paris Barraza is a reporter covering Los Angeles and Southern California for the USA TODAY Network. Reach her at pbarraza@usatodayco.com.
This article originally appeared on USA TODAY: What is rotavirus? Los Angeles County sees an increase in levels
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