Research is active into the virus' effects on the immune system in patients coinfected with GBV-C and HIV.

[6] Several but not all studies have suggested that coinfection with GBV-C slows the progression of HIV disease.

[8] It has a single-stranded, positive-sense RNA genome of about 9.3 kb and contains a single open reading frame (ORF) encoding two structural (E1 and E2) and five nonstructural (NS2, NS3, NS4, NS5A, and NS5B) proteins.

[1] GBV-C is a member of the family Flaviviridae and is phylogenetically related to hepatitis C virus, but replicates primarily in lymphocytes, and poorly, if at all, in hepatocytes.

[13] GBV-D may be ancestral to GBV-A and GBV-C.[13] The mutation rate of the GBV-C genome has been estimated at 10−2 to 10−3 substitutions/site/year.

About 10–25% of hepatitis C-infected patients and 14–36% of drug users who are seropositive for HIV-1 show the evidence of GBV-C infection.

[16] Genotype 5 appears to be basal in the phylogenetic tree, suggesting an African origin for this virus.