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article imageFood-borne infections caused by the Norovirus (Part 1)

By Karen Graham     Mar 9, 2016 in Food
A Chipotle Mexican Grill restaurant in Billerica, Massachusetts was closed on Wednesday because one of four sick employees tested positive for Norovirus.
Chipotle spokesman Chris Arnold was quoted by Food Safety News as saying, “After learning that four of our employees were not feeling well, our restaurant in Billerica, MA was closed for a full sanitizing."
“No customers’ illnesses are connected to this restaurant. Any employees who reported feeling ill will be held out of the restaurant until they fully recover.” There was no mention of how long the restaurant would remain closed or if the food on the premises would be thrown out. It is not known if all employees were tested for the virus.
The winter vomiting bug
Norwalk virus is also known as the winter vomiting virus. The virus is named after Norwalk, Ohio, in the United States, where an outbreak of acute viral gastroenteritis occurred among children at Bronson Elementary School in November 1968. Norwalk virus is the only species of the genus Norovirus, which belongs to the family Caliciviridae. This is probably why everyone calls the illness norovirus.
Whether it's called Norwalk or norovirus, it is very contagious, and anyone can pick it up. You can also have a norovirus illness many times in your life. It was thought at one time a person developed an immunity to the bug, but after about six months, that immunity starts to disappear, and by two years, it is gone.
So how is the norovirus spread and why is it important that food handlers not work if they are sick with the virus? For everyone concerned, the virus can be spread by infected people through direct contact with other people, or can contaminate food or drinks prepared by infected people. This makes children especially vulnerable to getting and spreading a norovirus infection.
The norovirus is also spread as an aerosol when someone has vomited or flushes the toilet after having a bout of diarrhea. The virus particles remain in the air and can be breathed in by other people. The virus can also live on surfaces and thrives quite well on produce, shellfish, ready-to-eat foods touched by infected food workers (salads, sandwiches, ice, cookies, fruit), or any other foods contaminated with vomit or feces from an infected person.
The CDC estimates that norovirus causes 19-21 million illnesses and contributes to 56,000-71,000 hospitalizations and 570-800 deaths annually in the united States. Norovirus is also the most common cause of food-borne illness in the country, with food handlers being the cause of 70 percent of norovirus outbreaks caused by contaminated foods.
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CDC
Incubation period and symptoms of norovirus
Norovirus is most prevalent between November and April every year, although it can occur at other times. The incubation period is anywhere from 12 to 48 hours. The symptoms of a norovirus infection include diarrhea, vomiting, nausea, and stomach pain. Diarrhea tends to be watery and non-bloody. Interestingly, diarrhea is more common in adults and vomiting is more common in children.
People with the norovirus can shed millions of virus particles, but it has been proven that as little as 10 to 18 virus particles can cause an infection. While it is true that a person is most contagious when they are vomiting or have diarrhea, a person can infect others as the symptoms are developing and for a number of days after they get over the illness. This could very well present a problem in places where food is served.
In Part 2 we will look at ways to prevent food-borne illness caused by norovirus, in our homes and in the workplace. In the meantime, always wash your hands before handling any foods and stay healthy.
More about foodborne illness, Recalls, Norovirus, norwalk virus, winter vomiting bug
 
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