Magazine article Science News

Model Explains Bubonic Plague's Persistence

Magazine article Science News

Model Explains Bubonic Plague's Persistence

Article excerpt

After bubonic plague reached Europe in the 14th century, major cities such as Venice enacted strict quarantines intended to keep out infected, shipborne rats. The cities would remain free of the disease for a time, but every decade or so, the plague returned. People have presumed that infected rats had sneaked back into town.

Challenging that assumption, computer modeling of how bubonic plague spreads from rats to people now suggests that the disease never went away. It probably persisted in the rat populations living in the cities, say Matthew J. Keeling and Chris A. Gilligan, both of Cambridge University in England.

Beyond suggesting that bubonic plague can lurk within rat populations for years without causing human epidemics, Keeling and Gilligan's work published in the Oct. 19 NATURE comes to the counterintuitive conclusion that killing rats may sometimes exacerbate plague outbreaks among people.

"There's a lot here for public health officials to think about," says Ben Bolker of the University of Florida in Gainesville, who also models infectious diseases.

Before looking into the plague for this new work, says Keeling, he felt the disease was of only historical interest. Yet bubonic plague has made a comeback, he notes. In the 1990s, it struck Africa and India, and scientists found that the bacterium responsible has developed antibiotic-resistant strains.

Past efforts to model bubonic plague treated it as primarily a human disease, which is inappropriate, says Keeling. "It's a rodent disease that occasionally infects humans," he explains. The fleas that transmit the plague feed upon people only when the disease wipes out so many rats that the insects turn to another food source.

By showing human outbreaks about every decade, the computer analysis by Keeling and Gilligan mirrors historical records of plague epidemics in medieval Europe. …

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