More In This Article The deadly outbreak of an illness that used
to infect only animals but now jeopardizes the survival of all
humanity has long been a standard thriller movie plot (think
Contagion or the 1995 classic Outbreak). Whereas reality usually
unfolds at a slightly less frenetic pace, the growing threat
from emerging diseases is nonetheless very real. Over the past
three decades we have witnessed the appearance of HIV/AIDS, mad
cow disease, H5N1 (avian flu) and the brain-damaging Nipah
virus—just to name a few. More recently, obscure poxvirus
infections such as monkeypox and cowpox have started to expand
their borders. Mounting population pressures and the spread of
rapid global transportation are fueling the emerging infections
trend. Tracing the chain of unintended consequences that lead
toward illness can be quite difficult, however. To give one
example: Lyme disease took off in the northeastern U.S. as more
and more people moved to previously wooded areas, displacing the
wolves who used to keep