Recently discovered blood-borne viruses.

In recent years, molecular biology advances have enabled many investigators to discover a number of viruses that have been difficult to characterise by cell culture techniques. Two blood-borne viruses have been identified. These are GB virus C (GBV-C) and TT virus (TTV). GBV-C was discovered in 1995. It is a flavivirus-like enveloped particle measuring 50-100 nm in diameter with a density of 1.08-1.13 g/cm3. The genome of GBV-C is a single-stranded, positive strand ribonucleic acid of approximately 8600 nucleotides. The TTV was discovered in 1997. It is a circular single-stranded deoxyribonucleic acid virus, non-enveloped of approximately 3900 nucleotides. It has a density of 1.31-1.34 g/cm3 and a particle size of 30-50 nm. Both viruses are distributed widely throughout the world. Most GBV-C infections are asymptomatic, transient and self-limiting. To date, solid evidence for any association of TTV with disease has not been demonstrated.