Three-quarters of emerging infectious diseases originate in animals, research suggests, as do widespread pathogens such as HIV, writes University of Iowa epidemiologist Tara Smith. She explores the connections between animal species and zoonoses including influenza, rabies, SARS and hantavirus. Smith points out that humans can also transmit pathogens to animals. For example, research has indicated humans can pass antibiotic-resistant Staphylococcus aureus to animals including chickens, dolphins and pigs.