From the WebMD Archives

Feb. 17, 2017 -- Schools from Rhode Island to California have closed down for days this winter after students and teachers became ill with what is believed to be norovirus, public health officials say.

Norovirus, incorrectly called the "stomach flu," is a short-term illness that's different from the flu. It strikes about 20 million  people a year in the U.S., most commonly in the winter, and causes a few days of misery, with diarrhea, nausea, vomiting, and abdominal pain.

In England, norovirus infections recently hit a 5-year high, according to Public Health England. Despite numerous U.S. school closings, the CDC says there is nothing unusual so far about this year's norovirus season.

"We are currently seeing the typical increase in norovirus outbreaks during the winter season," says Ian Branam, a CDC spokesman.

In December 2016, 175 suspected or confirmed norovirus outbreaks were reported by the nine states participating in the CDC norovirus reporting network, compared with 72 in December 2015. From Aug. 1 to the first week of January, the states reported about 400 outbreaks.

In an outbreak, more than the usual or expected number of people within a specific geographic area have a disease.

Norovirus is one of many bugs that can cause such symptoms.

"It has been a bad year for stomach viruses, but whether it's norovirus or not is hard to say," says Dennis Woo, MD, a pediatrician with UCLA Health in Santa Monica, CA. "Most of the time, it isn't diagnosed as norovirus unless there is a huge  outbreak," he says. If it's not an outbreak, a doctor is likely to tell the patient, based on symptoms, that it is some sort of virus, he says.

Easy to Catch

It isn’t surprising that schools are being hit hard with norovirus, says William Schaffner, MD, and infectious disease specialist and a spokesman for the Infectious Diseases Society of America. "The norovirus usually affects children, and usually children in a congregate setting," he says. So the virus can spread easily in schools and day-care centers.

It’s transmitted person to person, by eating contaminated food or water or by touching contaminated surfaces. The virus can live on surfaces for a long time, says Schaffner, a professor of preventive medicine at Vanderbilt University. "It's so easy to give norovirus to somoene else and to catch it because it takes so few [virus particles] to make you sick," he says.

He estimated that about 10 viral particles are enough to transmit the infection. In comparison, he says, hundreds of thousands of bacteria are needed to cause a salmonella infection.

Symptoms often come on within 24 to 48 hours of exposure. "It's an illness that usually lasts 2 to 4 days," Schaffner says. "You are miserable. It's thoroughly unpleasant." Patients are often coping with simultaneous diarrhea and vomiting, he says.

Treatment includes drinking plenty of fluids to stay hydrated. If dehydration is suspected, get medical attention.

Infected people are contagious the moment they begin feeling sick and for a few days after they recover, or even longer, the CDC says. The virus can remain in the stool for 2 weeks or longer.

Death from norovirus is not common, but hospitalization is. The CDC says that each year, the virus leads to about 56,000 to 71,000 hospitalizations and about 570 to 800 deaths.

Young children, older adults who are frail, and people with underlying diseases are most likely to die from norovirus, Schaffner says. And dehydration "almost certainly plays a role." 

Preventing Norovirus

Experts say it’s not easy to develop a vaccine for norovirus, partly because the virus can change. "Every 3 or 4 years, we have new strains emerging," says Abimbola Kolawole, PhD, a research investigator at the University of Michigan Medical School who has studied noroviruses.

Scientists at Baylor University discovered recently how to produce the virus in the lab, and that will speed research, Kolawole says. At least two companies have started tests for their norovirus vaccine. "Someday, we may be able to develop a vaccine that will be effective against multiple strains," Kolawole says.

Meanwhile, the CDC suggests these measures to lower the chance of getting sick and of transmitting the infection:  

  • Wash your hands with soap and water thoroughly and often. Hand sanitizer should supplement regular hand-washing, not replace it.
  • People infected with norovirus should not prepare food while sick and for at least 2 days after recovering.
  • Disinfect surfaces that may be contaminated with norovirus.
  • Wash fruits and vegetables thoroughly, and cook seafood well.

Show Sources

Ian Branam, CDC spokesman.

Dennis Woo, MD, pediatrician, UCLA Health, Santa Monica, CA.

William Schaffner, MD, professor of preventive medicine, Vanderbilt University, Nashville; infectious disease specialist and spokesman, Infectious Diseases Society of America.

BMJ: "Norovirus infections in England hit highest rate for five years."

Abimbola Kolawole, PhD, research investigator, University of Michigan Medical School, Ann Arbor.

ABC7 Chicago: "Norovirus Confirmed Cause of Widespread St. Charles School Stomach Virus."

Providence Journal: "Woonsocket elementary school cancels classes due to norovirus outbreak."

The Wall Street Journal: "The Stomach Bug Norovirus Rips Through U.S. Schools."

© 2017 WebMD, LLC. All rights reserved. View privacy policy and trust info