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The narrow gap between animal and human viruses

Yale Medicine Magazine, 2019 - Summer


When a pet prairie dog bit a 3-year-old in Wisconsin in 2003, the child contracted an infection endemic to central and western Africa. How had the monkeypox virus reached the American Midwest?

This is the kind of puzzle —and peril—that Warren A. Andiman, MD, FW ’76, explores in Animal Viruses and Humans: A Narrow Divide. The book teaches readers about the biological mechanisms that allow zoonotic viruses to move from animals to humans and gives detailed accounts of viral outbreaks, including the severe acute respiratory syndrome (SARS), rabies, and Ebola. Andiman, professor emeritus of pediatrics and public health at Yale, also addresses the political, economic, and environmental forces that are escalating the threat of zoonoses worldwide

In the case of the Wisconsin girl bitten by her pet, it turns out that an exotic-pet dealer in Illinois had housed prairie dogs with rodents imported from Africa, including a Gambian rat carrying monkeypox. Several other Midwesterners got sick, but nobody died, and no monkeypox has since been reported in the United States.

The prairie dog story illustrates Andiman’s understanding of why viruses threaten us “have mutation, will travel.” Because they mutate “promiscuously,” he explains, “viruses, unlike most living organisms, have found ways to populate every nook and cranny of the entire planet.” And if they aren’t in our cranny now, they could be soon—global travel, climate change, and refugees on the move have increased contact between animals and crowds of humans. Animal groups that carry five or more viruses that can infect us include birds, bats, pigs, primates, and rodents. To those carriers, add insects. “Imagine throwing billions of biting insects into the already swirling cauldron of animals and humans …” Andiman remarked.

When SARS appeared in southern China and began spreading in 2003, researchers around the world rallied to work on vaccines and antivirals, but the epidemic ended without the help of either. The same thing happened during the 2014-2015 Ebola outbreak in West Africa. Therefore, drug development doesn’t appear in Andiman’s “holy trinity” of zoonotic disease control; it requires too much time and money. Instead, local and national engagement come first in stemming transmission, including locating patients and tracing contacts; isolating the sick; minimizing stigma; alerting global health officials the minute an outbreak is discovered; and accepting outside help. Second, avoiding epidemics requires perpetual surveillance, perhaps even testing people working with pigs, such as the half-million Americans employed by the pork industry.

The third constituent of the trinity is foreign aid: building treatment centers, improving roads, and providing protective clothing for health workers and cold chains for medications. Foreign aid can support what Andiman described in an interview as “very basic public health practices we’ve known about for a hundred years: clean water, clean food, clean hands. When you give aid, you are helping yourself and your countrymen, because these viruses are borderless agents. There are no real borders anymore.”

Andiman knows something about borderless viruses. He and nurse practitioner Leetha Fraulino established the first AIDS program in New Haven in 1982, at a time when health care workers risked their own lives. “We didn’t even know it was a virus, and we knew nothing about the way it was transmitted. I was very worried.” He directed the Pediatric AIDS Care Program at Yale New Haven Hospital for 32 years. When the program began, one in five mothers with HIV passed the virus on to their babies. By 1996, policies governing testing and patient care had brought the transmission rate to zero.

Andiman imagined an audience of educated but non-expert readers during the two years he spent writing Animal Viruses and Humans. His aim was to explain how the control of zoonotic diseases can benefit all of us in “the family of humankind.”

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