animals they ve caught. this money is potentially infected with retroviruses. but virus hunter, dr. nathan wolf, is concerned about what unknown viruses these animals might carry, viruses that could make their way into the human population, touching off a pandemic. there is at least three viruses that you know about which are in this particular monkey? this species, yeah. and there s many, many more pathogens that are present in these animals. these individuals are at specific risk, particularly depending on the level of contact. if there s blood contact, they re at risk for transmission and potentially infection with novel viruses. reporter: as the hunters display their kills, something surprising happens. they show us filter paper they ve used to collect the animal s blood. the blood will be tested for e zoonotic viruses, part of a program dr. wolf has spent years setting up. does it surprise you that we ve run into two groups of hunters and they re all carrying the filter pa