Human B19 parvovirus infection: an example of multiple pathogenic effects determined by differences in host susceptibility.

B19 infection offers some general lessons about human viruses and their possible effects on the human host, as follows: (1) Ubiquitous apparently benign viruses may have severe effects on a compromised host. The virus may be invariable but the host can have diverse susceptibilities. (2) B19 and some other human viruses (though for none is the evidence so clear as for B19) have narrowly targetted effects. The host cell of B19 is a specialised progenitor of mature red cells: impairment of the function of this cell by B19 may cause profound anaemia. (3) The 'normal' host response to B19 may also cause disease, though this is self limiting. (4) The effects of malfunction of the virus' target cell are exacerbated when the immune response is impaired by congenital or acquired immunodeficiency, immunosuppressive therapy or, in the case of the fetus, developmental immaturity that allows the virus to persist.

Human parvovirus (B19) and erythema infectiosum.

An outbreak of erythema infectiosum ("fifth disease") was studied in Fukuoka, Japan, in 1980-1981. Human parvovirus (HPV) antigen was not detected in any patients, but anti-HPV, measured by countercurrent immunoelectrophoresis, was found in 33 of 34 affected children and in 21 (15%) of 141 children of the same ages without the disease. Immunoglobulin M class anti-HPV was present in all 25 children with erythema infectiosum tested. In a survey of hospital patients, the prevalence of anti-HPV detected by CIE was 12% in the cohort 5 to 9 years of age, 19% in the cohort 10 to 14 years, and 32 to 55% in the cohorts greater than or equal to 30 years. The antibody reactions in the cases of erythema infectiosum, which were already well established at the onset of disease, indicate that HPV was the cause of the outbreak.