In search of human protoparvovirus acute infections

Three protoparvoviruses (PPV)-bufavirus, cutavirus, and tusavirus-are the most recent members of the Parvoviridae virus family discovered in humans. All were initially found in stool but have since then been associated with gastroenteritis or cutaneous T-cell lymphoma, or found to be of zoonotic origin, respectively. In the current study, we developed novel PPV IgM enzyme immunoassays (EIA) and aimed to search for and characterize human protoparvovirus acute infections. We also provide a more comprehensive analysis of PPV seroprevalences. We screened, with in-house IgG, IgM, and PCR assays, a total of 1444 serum samples from ten different cohorts from six countries (Finland, Italy, Kenya, Latvia, Iran, and Iraq), with subjects varying in age and health status (e.g., unexplained fever, gastroenteritis, respiratory tract infections, chronic conditions, or constitutionally healthy). The geographic distributions of bufavirus seroprevalences were similar to previous findings, with a high (68 %) bufavirus seroprevalence found in Iran adult and low (<16 %) in Finnish elderly and Italy adult cohorts; the Iran child bufavirus seroprevalence was also significantly higher (16.5 %) than that of the Italy child cohort (4.5 %). Interestingly, we found surprisingly high (>10 %) cutavirus IgG seroprevalences among adults with chronic diseases and the elderly. We did not find any TuV IgG in any cohort. We also discovered some elevated human protoparvovirus IgM reactivity, but upon confirmatory competition EIA and PCR, none were true acute infections. These results suggest that acute human protoparvovirus infections are mild, local, rare, or not seen in respiratory tract infections or gastroenteritis.