The Black Plague

NEW WORLD/PLAGUE

50N E W S W E E K 0 1 / 1 3 / 2 0 1 7

THE PLAGUE is best known for wiping out as much as a third of Europe’s population during the Black Death pandemic of the 14th century, but it’s not entirely a thing of the past. It’s enough of a present-day threat—either as a potential bio- terrorism weapon or because some strains are now antibiotic-resistant—that some scientists are trying to develop a vaccine.

Dr. Ashok Chopra and a team of researchers at the University of Texas Medical Branch at Gal- veston recently published a study in the journal Nature of the three newest vaccine candidates. “So far, it looks very promising, at least in the two animal models we have tested,” says Chopra, a professor of microbiology and immunology. He began studying the bacterium that causes the plague, Yersinia pestis, around 2002.

His move into plague research followed the anthrax attacks of 2001, when letters containing anthrax were mailed to media outlets and congres- sional o� ces. Congress required the departments of Health and Human Services and Agriculture to regulate certain biological agents and toxins that could pose a severe threat to public health. The bacteria responsible for the plague made the top section of the list—Tier 1, the microbes most likely to be used as bioterrorism agents, alongside anthrax, Ebola and smallpox.

But 2001 wasn’t the � rst time the plague was considered a potential bioterr weapon, says Dr. Paul Mead, a medical epidemiologist with the

Centers for Disease Control and Prevention (CDC). Japan may have spread plague-infected � eas in China during World War II, and both the U.S. and the Soviet Union considered spreading the plague bacteria as an aerosol during the Cold War.

A PLAGUE ON ALL YOUR HOUSES There are three types of plague infections. Bubonic plague infects lymph nodes near the site of infection—usually the result of a � ea bite. Septicemic plague describes what happens when the infection spreads to the bloodstream. And pneumonic plague refers to lung infection. All are caused by Yersinia pestis.

Left untreated, the bubonic form has a 40 per- cent to 70 percent mortality rate. Pneumonic and septicemic plague are virtually always fatal.

In the pre-antibiotic era (1900–1941), the mor- tality among those infected with plague in the U.S. ranged from 66 percent to 93 percent. But antibiotics such as streptomycin and gentami- cin are used to treat all three strains now, so that mortality has been reduced to 11 percent.

According to the World Health Organization, there were 783 cases of the plague reported world- wide in 2013, including 126 deaths. It a� ects peo- ple in rural areas in central and southern Africa; central Asia and the Indian subcontinent; the northeastern part of South America and parts of the southwestern U.S. The three most heavily

BACK IN BLACK Plague, the scourge of the Middle Ages, is now rare, but its potential as a bioterror weapon has led to a search for a vaccine

BY LYDIA ZURAW

@lydiazuraw Kaiser Health News

5 1N E W S W E E K 0 1 / 1 3 / 2 0 1 7

H U

LT O

N -D

E U

T S

C H

C O

L L

E C

T IO

N /C

O R

B IS

/G E

T T

Y

a� ected countries are Madagascar, the Democratic Republic of Congo and Peru. According to the CDC, the U.S. sees an average of seven human plague cases each year. In 2015, there were 16 cases, including two teenagers who visited Yosemite National Park in California. Four of the 16 were fatal. As of early November, only four cases had been reported this year and all patients recovered, according to the CDC.

Vaccines for the plague exist, but they have some serious � aws. One that was made with dead bacteria and is approved by the U.S. Food and Drug Administration is no longer manu- factured. It protected against only the bubonic plague, not the more dangerous pneumonic plague. Another vaccine is used in areas where the bacteria are endemic, but it’s not approved by the FDA because of its high likelihood to cause severe side e� ects, such as fever and headaches. The vaccines Chopra discussed in Nature protect against the pneumonic plague and don’t cause side e� ects.

To prepare the candidate vaccines, the researchers deleted three genes in each of three candidate strains of plague in order to weaken the bacteria, but not kill them. The strains could no longer cause disease, but they generated a robust

immune response in the animals tested. The team gave two doses of each vaccine to mice and then challenged the animals’ immunity with highly virulent plague strains. The mice were protected up to four months later. Two of the mutant strains were also successfully tested in rats.

Chopra also has a plague vaccine in the works that uses the bacteria’s antigens (substances that trigger an immune response) rather than whole bacteria. In tests in nonhuman primates, it was shown to be highly protective.

“Everybody’s immune system is di� erent, so some people could be protected and some may not be,” Chopra says. His goal is to “have in our pipeline several vaccine candidates.”

BOTH THE U.S. AND THE SOVIET UNION CONSIDERED SPREADING PLAGUE BACTERIA AS AN AEROSOL DURING THE COLD WAR.

+ BLACK DEATH: A

chapel made from bones of people

who perished from the plague during

the Middle Ages. The disease is

enough of a current threat that scien- tists are trying to

develop a vaccine.

This story was written exclusively for Newsweek by Kaiser Health News, part of the nonpartisan Henry J. Kaiser Family Foundation.

Copyright of Newsweek Global is the property of Newsweek LLC and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use.