“It’s been on national lists as one of the more serious biological agents for a long time,” says Tom Ingelsby, director of the Center for Biosecurity of the University of Pittsburgh Medical Center. Plague bacteria lack the hard spores that makes anthrax so durable, but because it spreads so easily and kills more than one-third of those it infects in developing countries, the Centers for Disease Control and Prevention considers it a Category A bioterrorism agent, alongside smallpox and Ebola.
Plague as a biological weapon is not new. During World War II, Japanese planes reportedly dropped plague-infected fleas over Chinese settlements, and scientists in the former Soviet Union made large quantities of plague, potentially including drug-resistant varieties, for warfare.
According to the World Health Organization, about 100 pounds of aerosolized plague bacteria sprayed over a city of 5 million might sicken 150,000 people, fueling an epidemic, particularly if antibiotics were in short supply.
Such an epidemic is exactly what the CDC is trying to avert along the Uganda-Congo border, where nature, not bioterrorism, spreads the disease. According to epidemiologist Paul Mead of CDC’s division of vector-borne diseases in Fort Collins, Colo., new diagnostic tools and drugs will not only help Africans but also will provide a bulwark in the event of an outbreak or attack in the United States.
“We’re not going to completely eliminate plague,” Mead says, “but if we can put out the fire early on, we can reduce the deaths and economic impact.”
Rats and prairie dogs
Plague has spread with humanity and its rats to the burrows of prairie dogs in the Southwest and up the Nile River to remote corners of Africa. Far from being consigned to the Middle Ages, a 1994 outbreak in India resulted in 5,150 suspected plague cases and 53 deaths, which led the CDC to evaluate sick passengers arriving in the United States from India. Today, more than 1,000 plague cases are thought to occur globally each year, with more than 95 percent of them in Africa, particularly Uganda, Congo and Madagascar.
The plague bacteria, Yersinia pestis, typically makes the leap to humans as infected rats die, forcing fleas to find a new host. The best-known form of the disease, bubonic plague, results in painful, golf-ball-size swellings, known as buboes, in the lymph nodes of the groin or armpit. Plague can also cause hemorrhaging of blood vessels in the fingers and nose, leading to dark-purplish gangrene — hence the name “Black Death.” If bacteria reach the lungs, the pneumonic form of plague can spread from person to person through coughing. Untreated, plague is almost always fatal within a week, but identified within the first 24 to 48 hours, it can usually be cured with antibiotics.