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 Illustration by DZGNBIO
Human beings have faced new
diseases, and more deadly forms of old diseases, all through
history. Today fears of an epidemic are on the rise, fueled by
reports of exotic infections and antibiotic-resistant "super bugs."
Despite sophisticated modern techniques for tracking killer
pathogens, figuring out where the next deadly disease will come
from-and how to stop it-is not a simple task.
In June 2006, 46 fifth-graders and a dozen younger students in
Franklin, Massachusetts, came down with diarrhea, stomach cramps,
and fever. Doctors soon confirmed the kids had been infected with
Salmonella, a bacterial pathogen usually transmitted through
food. Food wasn't the culprit this time, though. This outbreak
stemmed from a class project in which the kids had handled owl
pellets, the wads of hair, bone, and other indigestible stuff owls
regurgitate after a meal. And when public health officials compared
the DNA fingerprint of Salmonella isolated from the students
and pellets with a nationwide database, they found a match.
"It was a strain which is really localized in Washington State,"
says Margaret Davis, a veterinary epidemiologist at Washington
State University. She studies the type of Salmonella known
as Typhimurium and had seen the fingerprint from the Massachusetts
case before. "As it turned out, they got the owl pellets from
Washington."
Salmonella is a hardy bug that gets around on food, owl
pellets, and unwashed hands, among other things. It has been making
people sick for centuries and still erupts distressingly often,
despite our sophisticated techniques for tracking it. In 1985,
Salmonella-tainted milk sickened up to 200,000 people in the
Midwest and killed at least two; in 1994, ice cream carrying the
bug sickened more than 3,000 people in 41 states.
Like other zoonotic diseases, which pass from animals to humans,
Salmonella poses special challenges with respect to
detection and control. With zoonotics we don't just have to monitor
human cases. Since the pathogens are harbored in animal
"reservoirs," we need to be aware of what's going on in animals as
well. It's a huge issue; infectious disease is the number-one cause
of death for humans worldwide, and many of the most frightening new
diseases we face are zoonotics. HIV came from apes; SARS started in
civet cats and perhaps bats; Ebola probably originated in bats.
While it often seems as if we see a new epidemic disease every
few years, Tom Besser, who heads WSU's zoonotic disease research
team, says the perception that outbreaks of scary diseases have
become more frequent or more deadly in recent decades is largely
due to better detection and reporting.
Still, outbreaks do happen. Besser, Davis, and other WSU
researchers are working to figure out how and why. What makes some
strains of a bug nastier than others? Why do they emerge when and
where they do? Are we more susceptible now than in the past, and if
so, why?
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