Little-Known Virus Sends Many Kids to Hospital

By Serena Gordon

HealthDay Reporter

WEDNESDAY, Feb. 13 (HealthDay News) -- Chances are you've never heard of human metapneumovirus. But, it's quite possible that you've been sick with this respiratory germ at some point in your life.

Discovered only 12 years ago, human metapneumovirus (HMPV) shares many symptoms with the flu. And, like the flu, most people who get it are miserable for a short time and then get better with no complications.

But the virus can cause serious illness, and in a recent study in U.S. children, researchers found that 6 percent of children who were hospitalized had HPMV, while 7 percent of pediatric emergency room visits were due to the virus.

"It turns out that human metapneumovirus is one of the most common causes of acute respiratory infections," said study senior author Dr. John Williams, an associate professor of pediatrics at the Vanderbilt University School of Medicine in Nashville, Tenn.

"Everyone knows about flu and RSV [respiratory syncytial virus], but it's just in the last couple of years that HPMV is making it into the medical school textbooks. For otherwise healthy children and adults, it tends to be a minor illness, like a cold, but populations that are vulnerable to one of these viruses are vulnerable to all of them," said Williams, who added that this generally includes the very young, the very old and people with underlying health problems, such as asthma or chronic heart disease.

"Now, that we've discovered this leading cause of respiratory infections in kids, it gives us a target for a vaccine," he noted.

The study was supported by a grant from the New Vaccine Surveillance Network of the U.S. Centers for Disease Control and Prevention. It was published in the Feb. 14 issue of the New England Journal of Medicine.

Human metapneumovirus was only discovered in 2001, though it was likely causing disease for many years before it was identified, according to background information in the study. And, although it's been a dozen years since the disease was discovered, it was still unclear how often people were infected, and how severe the illness could be.

To track down these answers, Williams and his Vanderbilt colleague Dr. Kathryn Edwards, along with other researchers, collected data on the virus from hospitals in three U.S. counties from 2003 through 2009.

They found the virus in 200 of 3,490 children (6 percent) hospitalized during that time period. Of 3,257 outpatient clinic visits, they found 7 percent of children had HPMV. And, of 3,001 children seen in emergency rooms, 7 percent had the virus. The researchers also tested 770 children who weren't having any symptoms, and found the virus in 1 percent.

Annually, one out of every 1,000 hospitalizations in children less than 5 years old was due to human metapneumovirus. In those less than 6 months of age, the rate of hospitalization due to HPMV was three per 1,000. In children aged 6 months to 1 year, that number was two per 1,000, according to the study.

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