Ahighly contagious virusthat causes vomiting and diarrhea is likely affecting some people in Los Angeles County.
Concentrations of norovirus, sometimes referred to as the "winter vomiting disease," detected in wastewater is increasing in the county, the Los Angeles County Department of Public Health told the USA TODAY Network in an email on Tuesday, Dec. 16. Officials use wastewater to monitor the presence of infectious diseases within a community, like norovirus or the virus that causes COVID-19.
The county public health department said that wastewater detection of norovirus increased 154% in Los Angeles for three weeks ending on Dec. 11. In Los Angeles County, wastewater detection of norovirus increased by over 250% for the same period.
Norovirus wastewater detection levels in the county are higher than levels reported for the same period last year, according to the public health department.
"Increasing norovirus concentrations in Los Angeles County indicate that the virus is likely spreading in Los Angeles County," the public health department said.
Norovirus: How does it spread?
Norovirus spreads easily through direct contact with someone who is infected, eating contaminated food, drinking contaminated water, or touching a contaminated surface and then touching your mouth. That's why county health officials encourage frequent handwashing, especially before eating or preparing food or using the bathroom, and washing fruits and vegetables "thoroughly."
While you can get sick with norovirus throughout the year, people fall ill with it most commonly between November and April, according to theCalifornia Department of Public Health. Last year, however, the "norovirus season" began earlier than in previous seasons, according to aresearch letterfrom the Centers for Disease Control and Prevention. In the U.S., the norovirus season typically starts in early December, but "the onset of the season was in early October 2024," according to the research letter.
Consumer Reports, the nonprofit known for testing and monitoring consumer-facing policy and products, released its annual risky food report in April, naming the 10 foods of 2024 that were subject to the most recalls and/or associated with the largest illness outbreaks. USA TODAY broke it down further on a what-you-need-to-know basis. " style="max-width:100%; height:auto; border-radius:6px; margin:10px 0;" loading="lazy" /> 
Deli meat is somewhat of a "risky" food as it is often associated with the spread of listeria, such as in the 2024 case of the Boar's Head listeria outbreak that killed 10. Listeria monocytogenes is a hardy germ that can survive in very low temperatures but thrives in cool and damp places. It can, and will, happily live on foods in your or your grocery store's storage area, and the process for mass-producing the meat lends itself to plenty of opportunities for contamination." style="max-width:100%; height:auto; border-radius:6px; margin:10px 0;" loading="lazy" /> 
Produce, like the cucumbers recalled due to a salmonella outbreak that infected 113 people across 23 states, can become adulterated with harmful bacteria through fecal contamination, which can occur through wastewater, water in the growing area, fertilizer and the proximity of the growing area to livestock." style="max-width:100%; height:auto; border-radius:6px; margin:10px 0;" loading="lazy" /> 
Raw dairy, which is always unsafe to consume and illegal to sell in some states, poses a risk when it's not pasteurized. Dairy pasteurization, or heating milk products to a high enough temperature to kill harmful bacteria, has been practiced since the 1920s and has resulted in illnesses commonly spread via milk, such as listeriosis, diphtheria and tuberculosis, becoming less prevalent." style="max-width:100%; height:auto; border-radius:6px; margin:10px 0;" loading="lazy" /> 
Cotija and queso fresco cheese are made from unpasteurized milk, meaning they carry an increased risk. One producer, Rizo-Lopez Foods, was shut down in October 2024 after its cheeses were linked to a years-long listeria outbreak that killed two people and made dozens of others sick." style="max-width:100%; height:auto; border-radius:6px; margin:10px 0;" loading="lazy" /> 
Eggs can become contaminated via the same means as cucumbers and other raw produce, especially if they have a cracked shell. " style="max-width:100%; height:auto; border-radius:6px; margin:10px 0;" loading="lazy" /> 
Like other raw produce, onions can become infected via fecal contamination. In 2024, E. coli-contaminated slivered onions on McDonald's Quarter Pounders triggered some locations to stop serving the burger temporarily. " style="max-width:100%; height:auto; border-radius:6px; margin:10px 0;" loading="lazy" /> 
Like cucumbers and onions, leafy greens are easily contaminated with bacteria like E. coli, as in the case of the Solata Foods spinach recall in 2024. " style="max-width:100%; height:auto; border-radius:6px; margin:10px 0;" loading="lazy" /> 
Organic carrots were linked to a major E. coli outbreak in late 2024, leaving at least 39 ill and one dead. " style="max-width:100%; height:auto; border-radius:6px; margin:10px 0;" loading="lazy" /> 
Ready-to-eat/cooked poultry and meat have been the source of multiple major recalls and foodborne illness outbreaks in recent years. The same issue arises with RTE foods as with deli meat; the conditions they are made and stored under are often ideal for bacteria such as listeria to grow. In 2024, millions of pounds of RTE foods were recalled by BrucePac for listeria contamination. " style="max-width:100%; height:auto; border-radius:6px; margin:10px 0;" loading="lazy" /> See the 'risky foods' linked to US recalls and illness outbreaks
Consumer Reports, the nonprofit known for testing and monitoring consumer-facing policy and products, releasedits annual risky food reportin April, naming the 10 foods of 2024 that were subject to the most recalls and/or associated with the largest illness outbreaks. USA TODAYbroke it down furtheron a what-you-need-to-know basis.
How long does norovirus last?
Symptoms usually last one to three days, according to the California Department of Public Health. Symptoms could onset as early as 12 hours after exposure, according to the county public health department.
How long is norovirus contagious?
According to studies, you may still be contagious for two weeks or longer even after feeling better, theCDC said.
Norovirus symptoms: Here's what to look out for
Norovirus commonly causes vomiting, diarrhea, nausea, and stomach cramps. But other symptoms of it can include fever, headache, and body aches.
Paris Barraza is a reporter covering Los Angeles and Southern California for the USA TODAY Network. Reach her atpbarraza@usatodayco.com.
This article originally appeared on USA TODAY:Norovirus 'likely spreading' in LA County. It's very contagious