, Volume 1, Issue 1, pp 25-28
Date: 21 Nov 2007

Views from Understanding Evolution: Parasites and Pathogens Take the Leap

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Even if you barely glance at the newspaper, it is hard not to feel that we have suddenly come under attack from a legion of pathogens. SARS, HIV, Ebola, West Nile Virus, and avian flu seem to have been quietly biding their time in other organisms before attacking human hosts en masse. But is that really the case? Are such emerging infectious diseases (EIDs) a new phenomenon? On DOI: 10.1007/s12052-007-0022-7 of this issue, Brooks and Hoberg (2007) take an evolutionary perspective on these bugs and reveal that such invasions are far from rare—or recent.

Although we first notice EIDs when they begin affecting human populations, these pathogens do not come out of nowhere. Generally, they are the longtime inhabitants of another animal (e.g., chimpanzees in the case of HIV, bats in the case of SARS) that have simply invaded a new host—who happens to be human. In this way, EIDs are just one example of a common evolutionary phenomenon: host-switching. A sapsucking insect species that previousl