The Spirit of John Snow (Guardians Part 3)
Posted by Richard Conniff on April 17, 2013
In fact, Richardson soon learned, TB is now resurgent, largely because delayed response to the AIDS epidemic gave it fresh ground to become active again, in the lungs of patients with weakened immune systems. The disease is treatable with an antibiotic cocktail, but the regimen is long and brutal. Some 1.4 million people die of TB each year, and 8.7 million new cases appear—more than triple the annual number of new HIV infections. Most of these TB cases are in Asia, India, China, and Africa. Air travel has contributed to London’s becoming an outpost of this new epidemic; even if Richardson had stayed home, he could have picked up the disease.
If Dr. Cetron grows nervous about this sort of thing, he also cites reasons for optimism: Until a few years ago, the international community had to rely exclusively on national governments to report public health emergencies. But governments often didn’t realize they had a problem until it was too late; they were also sometimes reluctant to report a problem that might hurt trade or tourism. Now, though, listening posts like the CDC’s Global Disease Detection Operations Center constantly scan news and social media in almost every language for hints of trouble. Moreover, regulations adopted in 2005 and backed by 194 nations allow outsiders to monitor internal media for public health emergencies. If a hospital is suddenly overwhelmed, the disease commandos are ready to spring into action.
“The ability to find an outlier, to detect an early event, has probably never been better,” says Dr. Cetron. Epidemiologists zoom in on “enigmatic events where we know that people are dying,” says Kira A. Christian, D.V.M., a CDC global disease analyst. “We know their signs and symptoms, their demographics. But we don’t know why.” Then they investigate. As with the coronavirus, it can mean that disease detectives must travel to some of the worst places on earth at the worst possible times.
Often these specialists come from the CDC’s Epidemic Intelligence Service, or EIS, an elite corps of young doctors, nurses, veterinarians, and other health professionals. In the apocalyptic 2011 movie Contagion, Kate Winslet plays the role of a fictional EIS officer, and real-life EIS officer Kevin Clarke, M.D., says he had to tell his mother to skip the film because (spoiler alert) “my character ends up in a body bag.”
Dr. Clarke, a 35-year-old pediatrician from Connecticut, recently returned from Zambia, where he’d been on the sort of mission the EIS undertakes 80 to 100 times a year. Doctors in Lusaka, the nation’s rapidly growing capital city, had become alarmed when their clinics suddenly filled with stricken children. The symptoms indicated typhoid fever, probably from contaminated food or water. But where and why? The Zambian government called in the EIS to help.
In Lusaka, local medical staff provided the first clues about which of the city’s densely populated new neighborhoods the typhoid victims came from. Then Dr. Clarke went in with Zambian public health workers and teams of local college students. Narrowing down the possible causes of an outbreak is mostly a matter of methodical, even mathematical, evidence gathering, says Eric Mintz, M.D., head of the CDC’s waterborne disease program. “But you have to know where to look and what to ask. And when you do, those John Snow moments are out there.”
Snow, now considered the father of epidemiology, was a pioneering physician during the London cholera epidemic of 1854. At a time when most doctors held their noses and blamed the disease on miasmas—foul air—Snow went door to door to map out exactly where the cholera was striking, and where it was passing by. His map led him to a single public well that had been contaminated with sewage—and the epidemic ended.
In Lusaka, Dr. Clarke and his team used the same strategy and soon identified areas where the municipal water supply wasn’t being adequately chlorinated. Not coincidentally, they were the same areas where typhoid fever was occurring. The team alerted local authorities, and a month later the epidemic came to an end. It was, he admits, the kind of result that makes EIS work “pretty rewarding.”