Chipotle Outbreak: How Does Norovirus Get into Restaurant Food?

The "stomach bug" norovirus is behind the latest outbreak of foodborne illness linked to Chipotle, according to health officials.

This week, a Chipotle restaurant in Sterling, Virginia, temporarily closed down after multiple customers reported falling ill with vomiting, diarrhea and stomach pains after eating there. A spokesman said the restaurant chain suspected that norovirus was to blame because the symptoms of the sick customers were typical of people infected with this virus, according to Reuters. But it wasn't until today (July 20) that health officials confirmed the cause of the illnesses after a customer tested positive for norovirus.

Norovirus is the most common cause of illnesses from contaminated food in the United States; an estimated 20 million Americans fall ill from the virus each year, according to the Centers for Disease Control and Prevention.

It's uncertain how norovirus got into the food at this particular Chipotle restaurant. But norovirus outbreaks at restaurants usually happen when a food service worker is sick with the virus and prepares food for customers, according to the CDC.

CDC research has found that, of the norovirus outbreaks involving contaminated food, 70 percent are caused by infected food workers.

Norovirus is very contagious because it does not take much to get you sick; as few as 18 virus particles on a person's hands or in their food can make them sick, according to the CDC. The number of norovirus particles that fit on a pinhead would be enough to infect more than 1,000 people, the CDC said. [Top 7 Germs in Food that Make You Sick]

People are most contagious while they are experiencing symptoms such as vomiting and diarrhea, but they can also spread the virus before their symptoms start and after they feel better.

To prevent the spread of norovirus, food workers should avoid preparing food while they are sick and for at least 48 hours after their symptoms go away, according to the CDC. They should also wash their hands carefully and often with soap and water, and avoid touching foods with their bare hands, the CDC said. In addition, companies in the food service industry can create policies that require workers to stay home when they are sick, and consider using paid sick leave and "on call" workers to support compliance with such policies, the agency said.

Chipotle closed its Sterling store for two days while workers performed "complete sanitizations" of all surfaces, according to Business Insider.

This isn't the first time a large outbreak of norovirus has been connected to a Chipotle restaurant. In 2015, more than 200 people became sick with the virus after eating at a Chipotle restaurant in Simi Valley, California, and 80 people got sick with the virus after eating at a Chipotle near Boston College, according to The Washington Post.

Also in 2015, Chipotle's food was linked with two separate outbreaks of E. coli that sickened 55 people in 11 states, and resulted in the chain closing 43 of its restaurants in Washington and Oregon, according to the Food and Drug Administration.

Original article on Live Science.

Rachael is a Live Science contributor, and was a former channel editor and senior writer for Live Science between 2010 and 2022. She has a master's degree in journalism from New York University's Science, Health and Environmental Reporting Program. She also holds a B.S. in molecular biology and an M.S. in biology from the University of California, San Diego. Her work has appeared in Scienceline, The Washington Post and Scientific American.