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11/8/06

NEW YORK (Reuters Health) - Human bocavirus (HBoV) is associated with respiratory tract infections, especially in infants and young children, according to two reports in the November 1st issue of The Journal of Infectious Diseases.

Human bocavirus is a recently discovered parvovirus that has been frequently detected among diagnostic respiratory samples, but its role in respiratory tract infections remains unclear.

In the first study, Dr. Peter Simmonds from University of Edinburgh, Scotland, and colleagues screened diagnostic respiratory samples for HBoV to investigate its involvement in respiratory disease.

HBoV was the third most frequently detected virus in the viral screening of 924 respiratory samples (most of which were from infants and young children), the authors report, after respiratory syncytial virus and adenovirus.

HBoV was most commonly detected in samples in which other respiratory viruses were present, the results indicate.

Detection of HBoV was most prevalent in December and January, the researchers note, and infections were almost completely confined to infants and young children. Its association with respiratory disease was similar to that of respiratory syncytial virus.

In the second study, Dr. Jeffrey S. Kahn and colleagues from Yale University School of Medicine, New Haven, Connecticut screened respiratory samples that were negative for other respiratory viruses for the presence of HBoV. The samples were obtained from children with or without respiratory symptoms.

Twenty-two (5.2%) of 425 samples tested positive for HBoV, the authors report, but none of 96 respiratory specimens from asymptomatic children tested positive for the virus. Symptoms experienced by HBoV-positive children included rhinorrhea in 90%, fever in 70%, cough in 70%, and wheezing in 50%, the investigators note.

A minority (30%) of infected children had hypoxia, the report indicates. In the 17 children who had X-rays performed, 12 had abnormal chest films.

"Our data suggest that HBoV is an etiological agent responsible for both upper and lower respiratory tract disease in infants and young children," the authors conclude. "Additional studies are required to completely define the epidemiological profile of this newly recognized pathogen."

"The most important contribution of (these studies) is that, for the first time, a substantial number of individuals without respiratory symptoms were included as controls, and HBoV either was not found or was found very infrequently in this group of individuals," writes Dr. Kenneth McIntosh from Children's Hospital Boston, Boston, in a related editorial.

"Finding, in two studies, a zero or very low incidence among control infants of the same age, sampled over the same time period in the same hospitals, is a huge advance, because it provides a statistical association of the virus with disease," Dr. McIntosh concludes. "It does not, however, prove causality, although it adds important corroborative support."

"The list of what we do not know is much longer than the list of what we do know," Dr. McIntosh adds.