Foamy viruses (FVs) or spumaviruses are complex retroviruses isolated in several mammal species like cats, cattle and horses. Highly prevalent in non-human primates they are not naturally present in humans, although several cases of simian-to-human transmissions have been described. Interestingly, the replication strategy of FVs differs in many aspects from that of other retroviruses, presenting features that are closely related to pararetroviruses, exemplified by the hepatitis B virus (HBV), but also characteristics that are closely related to yeast retrotransposons leding to the creation of the distinct Spumaretrovirina subfamily.
Keywords: complex retrovirus; foamy virus; spumavirus.