Colds Blamed on Newly Recognized Virus

Human Metapneumovirus Also Causes Wheezing, Sneezing, Other Respiratory Ills

Sept. 16, 2003 (Chicago) -- If your kid starts wheezing and sneezing this winter, a virus that no one even knew existed three years ago may be to blame, according to new research presented this week at the 43rd annual Interscience Conference on Antimicrobial Agents and Chemotherapy (ICACC) in Chicago.

The virus, known as human metapneumovirus, may be the second most common cause of wheezing, croup, pneumonia, and other respiratory ailments in infants and children, says lead researcher James Crowe Jr., an assistant professor in the department of pediatrics at Vanderbilt University in Nashville, Tenn.

And "it can cause the common cold, too," he says. "When it does, there's a good chance the ailment may be complicated by a middle ear infection."

Viral Detective Work

First identified by Dutch researchers in 2001, human metapneumovirus "is not a new virus, it's a newly discovered virus," Crowe says. The mysterious but ubiquitous microbe has probably been around for centuries -- or more, he says.

"It's amazing. Pediatricians have been saying that all these kids had respiratory syncytial virus, when in fact they had this," he says.

Usually referred to as RSV, respiratory syncytial virus is the No. 1 cause of bronchitis, pneumonia, and other respiratory ills in youngsters. This virus can also cause serious infections in the elderly and other people with chronic medical conditions.

Human metapneumovirus may explain why the wheezing and sneezing season seems to go on and on -- and on. According to Crowe, RSV season runs from November to March, while human metapneumovirus season is from December to April.

"As RSV wanes, human metapneumovirus peaks," he says. Since the two bugs cause similar symptoms and ailments, though, it just seems like one long season.

So how could such a common bug escape detection for so long? It was a matter of science lagging behind nature, Crowe explains. Human metapneumovirus doesn't grow well in cell cultures, the standard technology used for detecting new viruses. But in the last 10 years, refined molecular techniques have allowed scientists to analyze the genetic blueprints that make each virus distinct.

The good news: Now that the virus' molecular fingerprints are known, tests to detect the bug could be available within one or two years, Crowe says. Correct diagnosis is imperative to avoid misuse of antibiotics, which are effective only against bacteria, not viruses.

25-Year Study

In the new study, the researchers analyzed more than 5,000 nasal specimens taken over 25 years from more than 2,000 infants after they suffered severe respiratory illnesses.

Twelve percent of the samples were positive for human metapneumovirus. The bug also caused 15% of their common colds, about one-third of which were complicated by middle ear infections, Crowe says.

Fortunately, human metapneumovirus is rarely lethal, he adds, although 1 in 50 kids infected with the virus required hospitalization.

Elderly Affected, Too

Other experts say human metapneumovirus shows no evidence of age discrimination, striking the old as well as the young.

According to Ann R. Falsey, MD, associate professor of medicine at the University of Rochester School of Medicine in Rochester, N.Y., a recent study showed that nearly 3% of frail elderly adults were infected with human metapneumovirus, which was responsible for 10% of their hospitalizations in a year.

Compared with children, "the incidence goes down [in the elderly], but the impact goes up," she says.

In middle-aged adults, the virus seems to be milder, typically causing garden-variety colds.

"At least in [otherwise healthy] adults, we are figuring out whether it is a big deal. It is a little too early to say," Falsey says.

Global Impact

Other research shows the newly recognized virus knows no boundaries:

  • In a two-year Canadian study of more than 450 hospitalized children with respiratory ailments, 6% of those with severe pneumonia or bronchitis tested positive for human metapneumovirus, while 50% tested positive for RSV and 13% for the flu virus.
  • British researchers found that 8% of samples from 315 kids aged 6 months to 12 years who suffered from cough and fever during the winter months were positive for human metapneumovirus.
  • In an Israeli study of 40 healthy children, about half showed evidence that they had been exposed to the newly discovered virus by the time they turned 2 years old. And in a group of 25 8-year-olds who emigrated from Ethiopia, all showed evidence of infection, the researchers say.

Show Sources

SOURCES: 43rd annual Interscience Conference on Antimicrobial Agents and Chemotherapy, Chicago, Sept. 14-17, 2003. James Crowe Jr., assistant professor of pediatrics, Vanderbilt University, Nashville. Ann R. Falsey, MD, associate professor of medicine, University of Rochester School of Medicine, Rochester, N.Y.
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