Human bocavirus (HBoV) is one of many types of viruses that cause the common cold, respiratory infections, and gastroenteritis in humans. There are four genotypes in the genus Bocavirus that medical researchers have identified in the past several years since discovery of this virus in human specimens: HBoV1, HBoV2, HBoV3, and HBoV4. The researchers first isolated HBoV1 from respiratory secretions; they found the other strains primarily in stool samples.HBoV is a small single-stranded DNA virus in the Parvoviridae family of viruses. Health care professionals discovered HBoV in 2005 in nasal washing specimens from children with respiratory infection of unclear cause. About 3% of the specimens contained a bocavirus now called HBoV1. This discovery was made possible by new laboratory techniques, including PCR (polymerase chain reaction) testing to detect viral DNA.Health care providers have found human bocavirus throughout the world, mostly in pediatric cases, but it is not clear how significant or common a role it plays in human disease. Physicians often find HBoV along with another respiratory virus in sick individuals, there are no known HBoV infections in animals that health researchers can study, and it is very difficult to grow HBoV in the laboratory. Like parvoviruses, young children may shed HBoV for several weeks. It may be an "innocent bystander" in many individuals, it may cause infections by itself, or it may add to or worsen other viral infections. Recent cases suggest that it is capable of causing disease on its own, most often in individuals with underlying lung abnormalities or weak immunity.