Norovirus outbreaks sweep California

A stomach bug has been spreading across the country, including California, in recent months—leaving people feeling nauseous, achy, or worse.

There were 91 reported outbreaks of norovirus across the country during the week of Dec. 5, up from 69 outbreaks the previous week, according to the U.S. Centers for Disease Control and Prevention.

The CDC defines an outbreak as the occurrence of two or more similar illnesses resulting from a common exposure that is either suspected or laboratory-confirmed.

How does norovirus spread? What are common symptoms? And how can you avoid getting sick?

Here’s what you need to know:

What is norovirus?

Norovirus is a highly contagious virus that causes acute gastroenteritis, an inflammation of the stomach or intestines, according to the CDC.

Although it’s sometimes referred to as the “stomach flu” or “stomach bug,” norovirus is not related to influenza, which is caused by the influenza virus, the agency explained.

Norovirus is the primary cause of vomiting, diarrhea, and foodborne illness in the United States, with over 2,500 norovirus outbreaks reported annually, according to the CDC.

People can get infected with norovirus year-round, but outbreaks are most common from November to April, with peak season typically occurring from December to March.

On average, norovirus leads to 19 to 21 million illnesses in the U.S. each year, with children under 5 years old, older adults, and individuals with weakened immune systems at higher risk of developing severe infections, the CDC stated.

How does norovirus spread?

Norovirus spreads easily and can affect anyone, with symptoms usually lasting one to three days.

The virus is most commonly transmitted in closed and crowded environments such as hospitals, nursing homes, child care centers, and schools, as per the California Department of Public Health.

There are various ways to contract norovirus, including:

• Eating or drinking contaminated food or beverages, including undercooked shellfish
• Touching a contaminated surface and then touching your mouth without washing your hands
• Direct contact with someone infected with norovirus
• Sharing a toilet or bathroom with an infected individual
• Accidentally swallowing water containing norovirus, such as in swimming pools
• Cleaning up vomit or diarrhea without wearing protective gear like gloves and a face mask

While norovirus is often associated with cruise ships, cruise-related outbreaks account for only 1% of all reported norovirus cases, according to the CDC. Acute gastrointestinal illness is relatively rare on cruise ships, the agency added.

What are the common symptoms of norovirus?

People typically experience symptoms 12 to 48 hours after exposure to norovirus, with the most common symptoms being:

• Diarrhea
• Vomiting
• Nausea
• Stomach pain
• Fever
• Headache
• Body aches
• Dehydration
• Decreased urination
• Dry mouth and throat

Can norovirus be fatal?

While most individuals recover from norovirus within a few days, the virus is linked to approximately 900 deaths annually in the United States, mostly among individuals aged 65 and older, according to the CDC.

Are there norovirus outbreaks in California?

California reported 55 laboratory-confirmed norovirus outbreaks from January 2024 to November 2024, according to the latest data from the state Department of Public Health.

In comparison, California experienced 73 outbreaks during the same 11-month period in 2023 and 56 outbreaks during the corresponding period in 2022.

The state saw its highest number of norovirus outbreaks in recent years in 2019, with a total of 76 reported outbreaks from January to November.

While health care providers are not required to report individual cases of norovirus to local health departments, they must report outbreaks, as stated by the California Department of Public Health.

The California Public Health Department recently detected elevated levels of norovirus in wastewater compared to December 2023 and January 2024, based on data collected by WastewaterSCAN, a research team from Stanford University that analyzes infectious diseases from wastewater treatment plants across the U.S.

How is norovirus treated? Is there a vaccine?

There is no specific treatment for norovirus, but the CDC recommends drinking plenty of water or other non-caffeinated, non-alcoholic beverages to prevent dehydration.

Over-the-counter medications like Imodium, Pepto-Bismol, and Kaopectate can help alleviate norovirus symptoms, according to the National Institutes of Health.

As of January 6, there is no vaccine available for norovirus, according to California Public Health Department spokesperson Grant Boyken.

What’s the best way to prevent getting sick?

Given the high contagiousness of norovirus, the CDC suggests following these tips to prevent illness and limit the spread of the virus:

• Wash your hands thoroughly and frequently
• Cook shellfish thoroughly and wash fruits and vegetables before consuming
• Clean and disinfect contaminated surfaces
• Wash laundry in hot water
• Stay home when sick and for 48 hours after symptoms subside

Boyken added, “Avoid preparing or handling food for others when you are sick and for two days after you recover.”

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