Metapneumovirus Hits Kids First

Laird Harrison

October 10, 2013

SAN FRANCISCO — Human metapneumovirus appears to spread from children to adults, a new study shows.

"Children expressed peak human metapneumovirus activity 3 days before the community midpoint," said Chris Stockmann, MSc, a graduate assistant at the University of Utah in Salt Lake City.

Stockmann made the first of 2 presentations on the epidemiology of the newly discovered virus here at IDWeek 2013.

Researchers first identified the virus in the Netherlands in 2001. They have since determined that it is one of the chief causes of respiratory illness in children, and leads to lower-respiratory infections, including bronchiolitis, and pneumonia. Treatment is supportive and there is no vaccine for the virus.

Human metapneumovirus has been detected in 6% of hospitalized children younger than 18 years.

To determine how the virus spreads, Stockmann and his team analyzed data from 21 hospitals and more than 100 doctor's offices in the Intermountain West region of the United States.

They defined the duration of a respiratory outbreak as the number of weeks per year in which at least 90% of cases occurred.

 
Children expressed peak human metapneumovirus activity 3 days before the community midpoint.
 

The midpoint of each respiratory outbreak was considered to be the week when 50% of the season's cumulative number of infections was reached. They performed this analysis for the entire cohort, and then separately by age group.

The researchers identified 4569 cases of human metapneumovirus over the study period, with a mean of 652 cases per season. The virus's activity peaked in children 5 to 11 years of age 3 days before the community midpoint.

In adults 19 to 64 years of age, peak activity occurred roughly 10 days after the community midpoint. In those older than 65 years of age, it occurred 20 days after the midpoint.

These findings suggest that "reducing infection in these younger age groups may have the potential to yield additional benefits, including a reduction of disease in older people," Stockmann noted.

After the presentation, John Williams, MD, associate professor of pediatrics at Vanderbilt University in Nashville, Tennessee, pointed out that testing is performed less often in adults, and wondered if this would bias the results. Stockmann said that his group performed an analysis looking at that question and found that the results held up.

National Surveillance

Following Stockmann's presentation, Daniel Johnson, MD, associate professor of infectious diseases at the University of Chicago, presented data on the human metapneumovirus from the National Respiratory and Enteric Virus Surveillance System (NREVSS).

Dr. Johnson, who was not involved in the study, presented the research of Amber Haynes, MPH, and her team from the US Center for Disease Control and Prevention in Atlanta, who could not attend the meeting because of the government shutdown.

The NREVSS passively collects results from specimens tested for respiratory viruses, including human metapneumovirus identified with reverse transcription-polymerase chain reaction (RT-PCR) and antigen detection methods.

From July 2007 to June 2013, the researchers tabulated weekly aggregates of tests performed, positive results, geographic location, week-ending date, and testing method (RT-PCR or antigen).

They defined onset as the first of 2 consecutive weeks when the weekly proportion of positive tests exceeded 3%. They defined offset as the last of 2 consecutive weeks when the weekly aggregate exceeded that threshold.

The researchers collected 379,013 RT-PCT tests and 414,087 antigen tests, with 5 to 61 laboratories reporting each season. Over the study period, the number of laboratories reporting increased, as did the number of states with at least 1 laboratory reporting the virus (from 5 to 23).

The same patterns of seasonality emerged for both antigen and RT-PCR. The season began near the middle of winter and continued into early spring. The activity of the virus appears to peak later in the winter than influenza or respiratory syncytial virus.

"Healthcare practitioners should consider testing for it in patients with respiratory disease," said Dr. Johnson.

Session moderator Keith Klugman, PhD, from Emory University in Atlanta, told Medscape Medical News that these studies should heighten clinicians' awareness of the disease.

"It's reassuring to parents to know what the cause of their child's disease is, and it's reassuring to the physician as well," he said.

Mr. Stockmann, Dr. Johnson, and Dr. Klugman have disclosed no relevant financial relationships.

IDWeek 2013: Abstracts 123 and 124. Presented October 3, 2013.

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