Dozens of diseases once limited to animals have reportedly infected humans during the past 20 years, with more expected to soon cross the genetic barrier.

Examples of diseases spreading from animals to humans that are emerging or re-emerging include HIV, hantavirus (from rodents), bird flu, rabies, malaria, West Nile virus (from mosquitoes), H1N1 influenza virus, SARS, and Lyme disease (from ticks).

United States Environmental Protection Agency (EPA) experts warn that a growing spread of diseases could result from environmental changes and more people moving into rural areas.

“We appear to be undergoing a distinct change in global disease ecology,” Montira Pongsiri, an environmental health scientist at the EPA in Washington, said. “The recent emergence of infectious diseases (such as swine flu and SARS) appears to be driven by globalization and ecological disruption” (The Independent).

David Murrell, lecturer in ecology at University College London, said, “Since 1940, over 300 new diseases have been identified, 60 per cent of which crossed to humans from animals and 70 per cent of these came from contact with wildlife. I would expect the emergence of new diseases from contact with animals to continue in this century” (ibid.).