HMPV a leading cause of community pneumonia

December 2006

Although respiratory synctical virus remains the No. 1 source for community-acquired pneumonia, human metapneumovirus is a second leading cause, particularly in children older than 12 months.

Dana Wolf, MD, a researcher at Hadassah University Hospital in Jerusalem, said community-acquired pneumonia is a leading cause of morbidity and mortality in children younger than 5 years of age.

“Human metapneumovirus has been shown to be a major player in lower respiratory infections, but its association with pneumonia had not been as well demonstrated,” Wolf said at the 46th Interscience Conference on Antimicrobial Agents and Chemotherapy in San Francisco.

An earlier study of 517 children who had been hospitalized for lower respiratory tract infection found a significant association between diagnosis and the presence of human metapneumovirus.

Wolf and colleagues sought to analyze the rate of human metapneumovirus in patients with community-acquired pneumonia.

The researchers focused their efforts at the Soroka University Medical Center, which is the only general hospital in Southern Israel. The hospital provides care to 520,000 people, of whom about 60,000 are younger than 5-years-old.

To be included in the study, patients had to be younger than 5 years of age and meet the radiologic criteria for community-associated pneumonia as defined by WHO. The presence of pneumonia was confirmed by two independent pediatric infectious disease specialists and a pediatric radiologist.

Second leading cause

Between November 2001 and October 2005, 3,507 children were admitted to the emergency department with pneumonia. Nasal specimens were collected in 1,296 children, of whom 997 were hospitalized and 299 were not.

Human metapneumovirus was identified in 108 children. Of these 108 children, human metapneumovirus was the only viral found in 84, whereas co-infections were noted in 24 children.

Overall, human metapneumovirus was noted in 8.3% of children, whereas respiratory syncytial virus was noted in 23.1%. The third most common virus in these children was adenovirus at 3.4%.

Community-acquired pneumonia associated with human metapneumovirus peaked in November through May, with about 88% of the cases seen during that time. During the four-year study period, human metapneumovirus was detected in 14.5% in year one, 5.8% in year two, 6.2% in year three and 12.2% in year four.

“Despite this year to year variability, human metapneumovirus was always the second leading cause of community-acquired pneumonia,” Wolf said.

Age groupings

When the researchers analyzed the data by age, they noted that among children with community-acquired pneumonia respiratory synctical virus was in 37% of children younger than 12 months, whereas human metapneumovirus was in 6.5%.

Among children older than 12 months, that gap narrowed with 11% having respiratory synctical virus compared with 6.5% with human metapneumovirus.

“The proportion of virus negative specimens increased from 36.9% to 67.1% during the first year of life,” Wolf said.

Human metapneumovirus was most commonly seen in children with a mean age of 19.1 months, whereas respiratory synctical virus was found in children with a mean age of 9.1 months. There was also a greater incidence of tympanocentesis at 18.5% with human metapneumovirus compared with 7.6% with respiratory synctical virus.

Children with human metapneumovirus were more likely to have a history of pneumonia at 29.9% compared with 13.5% among those patients with respiratory synctical virus.

However, there were no significant differences in gender, ethnicity, number of siblings, history of antibiotic use or history of asthma.

Human metapneumovirus was associated with a greater incidence of wheezing at 47.5% compared with 23.2% among those children with respiratory synctical virus. Children presenting with human metapneumovirus were also more likely to present with gastrointestinal symptoms like abdominal pain or vomiting (56.3% vs. 31.2%).

For more information:

• Wolf DG, Shemer-Avni Y, Greenberg D, et al. A major role for human metapneumovirus in alveolar pneumonia in young children. Presented at: the 46th Interscience Conference on Antimicrobial Agents and Chemotherapy; Sept. 27-30, 2006; San Francisco.