Study finds norovirus leading cause of acute gastroenteritis in infants, young children as rotavirus declines

ATLANTA — Norovirus has emerged as the leading cause of gastroenteritis — inflammation of the stomach and intestines — in children younger than 5 years, according to a new study.

The study, published in the New England Journal of Medicine, found that norovirus, the most common cause of stomach flu, was responsible for nearly 1 million doctor visits by children in the United States between 2009 and 2010, costing about $273 million each year. The researchers who conducted the study estimated there were 14,000 hospitalizations, 281,000 emergency room visits and 627,000 outpatient visits due to norovirus illness among small children. More than 21 million people in the United States get infected each year and develop acute gastroenteritis, and about 800 die; young children and elderly people are considered more likely to suffer from severe infections.

"Infants and young children are very susceptible to norovirus infections, which often result in a high risk of getting dehydrated from the sudden onset of intense vomiting and severe diarrhea," Centers for Disease Control and Prevention epidemiologist Daniel Payne said. "Our study estimates that 1-in-278 U.S. children will be hospitalized for norovirus illness by the time they turn 5 years of age. It is also estimated that about 1-in-14 children will visit an emergency room and 1-in-6 will receive outpatient care for norovirus infections."

CDC researchers tracked 1,295 infants and young children who sought medical care for acute gastroenteritis between October 2008 and September 2010, looking at more than 141,000 children in three U.S. counties. Lab tests for norovirus found it in 21% of the patients, compared with only 12% who had rotavirus. About half of the doctor visits due to norovirus infections were among infants ages 6 to 18 months, and infants and 1-year-old children were more likely to be hospitalized than older children. Still, overall rates of norovirus in emergency rooms and outpatient offices were 20 to 40 times higher than hospitalization rates.

"Our study confirmed that medical visits for rotavirus illness have decreased," Payne said. "Also, our study reinforces the success of the U.S. rotavirus vaccination program and also emphasizes the value of specific interventions to protect against norovirus illness."

According to the CDC, vaccines are currently being developed for norovirus.