In the interval 1994-1999, in Australia, Malaysia and Singapore, epizootic and epidemiological episodes of meningoencephalitis and severe acute respiratory syndromes were reported. Highly lethal in horses, swine and humans, the episodes were proved to be caused by the "new" viruses Hendra (HeV) and Nipah (NiV). At the same time three "new" viral agents have been isolated: Lyssavirus, Menanglevirus and Tupaia paramyxovirus. The intense contemporary circulation of people, animals and food products together with changes in human ecosystem favor new relations between humans and the "natural reservoirs" of biologic agents with a pathogenic potential for domestic and peridomestic animals and humans.