A highly contagious stomach virus commonly referred to as the “vomit bug” is rapidly spreading across several parts of the United States, raising concerns among health authorities and medical experts. The virus, identified as norovirus, has triggered outbreaks in multiple regions, including California, with reports of infections emerging from hiking trails, schools, healthcare facilities and other crowded places.
According to reports, several hikers travelling along California’s Pacific Crest Trail recently experienced severe gastrointestinal symptoms linked to the outbreak. Health officials in the San Francisco Bay Area have also reported a rise in cases, indicating that the virus is circulating widely across communities. Wastewater surveillance systems monitoring public health trends have detected high levels of norovirus activity in several parts of the country, especially in the Northeast and Midwest regions.
Norovirus is one of the leading causes of foodborne illnesses in the United States and is known for spreading extremely quickly. The virus causes acute gastroenteritis, an inflammation of the stomach and intestines, and is commonly called the stomach flu, although it is unrelated to influenza. Health experts said the virus spreads through contaminated food, water, surfaces and close contact with infected individuals. Even tiny particles from vomit or stool can transmit the infection, making it highly infectious in enclosed or crowded settings.
The Centers for Disease Control and Prevention’s NoroSTAT surveillance programme reported more than 1,100 norovirus outbreaks between August 2025 and early May 2026. Scientists monitoring the spread of the disease said that a newer strain, identified as GII.17, has increasingly become dominant in recent outbreaks. Experts believe the strain spreads more easily because many people have limited immunity against it.
Symptoms of norovirus usually begin within 12 to 48 hours after exposure and include sudden vomiting, nausea, diarrhoea, stomach cramps and fatigue. Some patients may also develop fever, headaches, chills and body aches. While most healthy individuals recover within one to three days, doctors warned that dehydration remains a major concern, particularly among children, elderly people and those with pre-existing medical conditions.
Medical experts advised people experiencing symptoms to stay hydrated by drinking fluids and electrolyte-rich beverages. They also recommended seeking immediate medical attention if severe dehydration, weakness or persistent vomiting develops. In some reported cases, infected hikers required hospitalisation after becoming severely dehydrated during outdoor trips.
Public health agencies have urged citizens to follow preventive measures such as frequent handwashing with soap and water, proper cleaning of contaminated surfaces and avoiding food preparation while sick. Experts noted that alcohol-based hand sanitisers are less effective against norovirus, making proper hand hygiene essential in controlling the outbreak.
Although norovirus outbreaks are more common during winter months, health officials said seasonal travel, gatherings and close indoor contact may be contributing to the current rise in infections across the country. Authorities continue to monitor the situation as cases emerge in different regions of the United States.
