Nucleic acid testing for emerging viral infections.

The development of new technologies leads to the discovery of new viruses. For each of these new infectious agents, relevance to transfusion, including transmissibility by transfusion, pathogenicity, prevalence in blood donors, persistence and the availability of screening assays needs to be assessed. Since 1995, one virus and a new family of viruses have been identified. GB virus-C/hepatitis G virus (GBV-C/HGV), a flavi virus with some homology with and epidemiological features of HCV, is not related to post-transfusion hepatitis but seems to positively interfere with human immunodeficiency virus replication. Human circoviruses include TT virus (TTV) and SEN-V. Both are highly variable, constituting a large family of distantly related viruses. They appear ubiquitous, infecting humans very early in life and are largely persistent. No clinical symptoms or pathogenicity is associated with TTV, but SEN-V might be associated with some non-A-E post-transfusion hepatitis. Parvovirus B19 has been known for many years, but its transmission to recipients of plasma derivatives despite viral inactivation raised the issue of screening plasma pools by nucleic acid testing. Most fractionators quantify B19 DNA in plasma pools to ensure a viral load of <10(4) IU mL-1.