'Cruise Ship Virus' Also Sickens 1 Million U.S. Kids Yearly

Norovirus has overtaken rotavirus in causing gastric illness, CDC study finds

By Serena Gordon

HealthDay Reporter

WEDNESDAY, March 20 (HealthDay News) -- Norovirus, the infamous stomach bug that's sickened countless cruise ship passengers, also wreaks havoc on land.

Each year, many children visit their doctor or an emergency room due to severe vomiting and diarrhea caused by norovirus, according to new research from the U.S. Centers for Disease Control and Prevention. The CDC report estimated the cost of those illnesses at more than $273 million annually.

"The main point we found was that the health care burden in children under 5 years old from norovirus was surprisingly great, causing nearly 1 million medical visits per year," said the study's lead author, Daniel Payne, an epidemiologist with the CDC. "The second point was that, for the first time, norovirus health care visits have exceeded those for rotavirus."

Rotavirus is a common gastrointestinal illness for which there is now a vaccine.

It's important to note that the rate of norovirus hasn't been increasing in young children, Payne said. The reason norovirus is now responsible for more health care visits than rotavirus is that the incidence of rotavirus infection is dropping because the rotavirus vaccine is working well.

Results of the study are published in the March 21 issue of the New England Journal of Medicine.

Norovirus is a viral illness that can affect anyone, according to the CDC. It commonly causes nausea, diarrhea, vomiting and stomach cramps. Most people recover from a norovirus infection in a day or two, but the very young and the very old -- as well as those with underlying medical conditions -- have a greater risk of becoming dehydrated when they're sick with norovirus.

The virus is very contagious. Payne said it takes as few as 18 norovirus particles to infect someone. By comparison, a flu virus may take between 100 and 1,000 virus particles to cause infection. Payne said people who have been infected can also keep spreading the virus even after they feel better.

Norovirus is difficult to diagnose definitively. The test that can confirm the virus is costly and time consuming, Payne said, so there have not been good data on how many children are affected by it each year.

To get a better idea of how prevalent this infection really is, the researchers collected samples from hospitals, emergency departments and outpatient clinics from children under 5 years old who had acute gastrointestinal symptoms. The children were from three U.S. counties: Monroe County, N.Y.; Davidson County, Tenn.; and Hamilton County, Ohio. The samples were collected in 2009 and 2010, and were tested for both norovirus and rotavirus.

Norovirus was detected in 21 percent of children under 5 in 2009 and 2010. Rotavirus was found in 12 percent of children in the same age group. Norovirus was also found in 4 percent of healthy children tested in 2009 .

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