Genetic diversity of human erythroviruses: Implications for B19 diagnosis

The acute B19 infection causes the childhood erythema infectiosum (exanthem fifth disease), frequently associated with arthralgia, In persons with und erlying hemolysis, acute B19 infection causes a transient aplastic crisis. The primary B19 infection in pregnant women can lead at worst to intrauteri ne fetal death. Chronic B19 infection are rare, except in immunocompromised patients, leading to anemia, thrombopenia, or even aplasia. The virus is g enerally transmitted between humans by the respiratory route, but infection can also be transmitted by blood or blood products. The genetic diversity of erythroviruses was thought until now to be very low, the maximum diverge nce is indeed lower than 1% (on the whole DNA sequence). A novel variant hu man erythrovirus was found recently from a child suffering from aplastic cr isis with severe acute anemia on glucose-6-phosphate deshydrogenase (G6PD) deficiency background. Phylogenetic analysis of part of VP1 gene revealed t hat V9 variant sequence was much more divergent from the B19 than these B19 sequences among themselves, with more than 11% and less than 7% divergence respectively. New diagnostic tests which can detect V9 infection ought to be developped, Such an infection indeed cannot be detected by standard diag nostic tests (either PCR of serology) which were designed for B19 and are n ot suitable for the diagnosis of such a divergent erythrovirus as V9.