To date, only one Human Pegivirus (HPgV-1) in the family Flaviviridae is known to exist, but we all know that nature is elusive and frequently manages to surprise.
Scientists recently discovered a novel pegivirus from plasma corresponding to a Hepatitis C Virus-infected patient who died from unknown sepsis. This virus, provisionally named Human Pegivirus-2 (HPgV-2), is highly divergent, sharing less than 32% amino acid identity with its nearest relatives, a bat and rodent pegivirus.
The evidence suggest that Human Pegivirus-2 is an infectious agent capable of bloodborne transmission.
Why didn't we know about this virus before? Notably, all 12 Human Pegivirus-2-infected individuals, including the index case, were co-infected with Hepatitis C Virus (genotypes 1a, 1b, or 2b), 3 co-infected with Human Pegivirus-1 and 2 co-infected with HIV. Maybe it was simply hiding from view.
Studies to date have suggested that pegivirus evolutionary lineages corresponding to each mammalian host tend to cluster together, consistent with a model of co-divergence of the virus with its host. This latest report of Human Pegivirus-2 infecting humans is consistent this pattern. Over 80 novel hepaciviruses and pegviruses have now been reported in bats, as well as multiple novel hepaciviruses in rodents, cattle and horses, underscoring the extraordinary diversity of these viruses in animal reservoirs.
 Berg at al: Discovery of a Novel Human Pegivirus in Blood Associated with Hepatitis C Virus Co-Infection in PloS Pathogens – 2015
 Quan et al: et al: Bats are a major natural reservoir for hepaciviruses and pegiviruses in Proceedings of the National Academy of Science – 2013