Indictment by Association: Once Is Not Enough.

Abstract

Early life infections with human bocavirus 1 (HBoV-1) are common, and the virus is readily detected in the upper respiratory tract, often during acute upper respiratory tract illness. Its etiological role in respiratory tract infections has been uncertain because of its presence in asymptomatic children and frequent concurrent detection of other respiratory viruses. Longitudinal cohort studies, in which sampling is done at intervals that include periods of illness and health, have begun to bring clarity to the story. In this issue of the Journal ,M artin et al [1] performed noninvasive weekly sampling and collected health data during the first 2 years of life and provide substantial evidence that HBoV-1 is indeed a respiratory pathogen in young children. This story is an excellent example of the power of longitudinal cohort study designs in identifying etiologic roles for viruses that embody combinations of being highly prevalent, being able to reinfect previously exposed individuals and to persist for long periods in the infected host in the absence of symptoms, and, often, causing mild disease. HBoV-1 HBoV-1 was discovered in 2005 by sequencing nonhost DNA present in nasopharyngeal aspirates that were collected during respiratory tract infections [2]. HBoV-1 is a DNA virus of the family Parvoviridae ,g enusBocaparvovirus (the name is derived from the hosts of the first characterized bocaviruses, bovines and canines), and species Primate bocaparvovirus 1, which also includes HBoV3. The Primate bocaparvovirus 2 species includes the somewhat more distantly related HBoV-2 and HBoV-4. There is very low sequence variability within the major strain groups. HBoV-1 VP1/2 amino acid sequences differ from their HBoV-2, HBoV-3, and HBoV-4 homologs by approximately 20%, whereas HBoV-2, -3, and -4 differ from each other by approximately 10% [3].The 4 HBoV strain groups appear to represent distinct virus species, but this awaits formal consideration by the International Committee for Taxonomy of Viruses. HBoV have a wide geographic distribution [3]. HBoV-1 is most commonly found in respiratory tract specimens, while HBoV-2, HBoV-3, and HBoV-4 are more frequently detected in stool specimens [4]. Laboratory diagnosis of HBoV is made