Wesleyan faculty frequently publish articles based on their scholarship in The Conversation US, a nonprofit news organization with the tagline “Academic rigor, journalistic flair.” In this article, Fred Cohan, professor of biology, Huffington Foundation Professor in the College of the Environment, PhD student Kathleen Sagarin, and Kelly Mei ’20 explain how viruses like coronavirus—and several others over history—spread from animals to humans, what determines the size of the outbreak, and how behavioral modifications and technology can stop the spread.
A clue to stopping coronavirus: Knowing how viruses adapt from animals to humans
As the novel coronavirus death toll mounts, it is natural to worry. How far will this virus travel through humanity, and could another such virus arise seemingly from nowhere?
As microbial ecologists who study the origins of new microbial species, we would like to give some perspective.
As a result of continuing deforestation, “bushmeat” hunting of wild animals and caring for our domestic animals, the novel coronavirus will certainly not be the last deadly virus from wild animals to infect humans. Indeed, wild species of bats and primates abound in viruses closely related to SARS and HIV, respectively. When humans interact with wild animal species, pathogens that are resident in those animals can spill over to humans, sometimes with deadly effects.
No new virus under the Sun?
Most “emergent” viruses that are new to humans are regular inhabitants of other species. In some cases, the animal hosts have reached a peaceful coexistence with their viruses, as in the case of bats. In other cases, the viruses are as deadly in their wild animal hosts as in us, as with chimpanzees and their immunodeficiency viruses. Human activities have increased the rate of spillovers of wild animal viruses into our species, particularly from bats.
Deforestation has brought bats closer to human habitations, resulting in recurrent spread of Ebola from bats to humans in sub-Saharan Africa. The trade in wild animals brought us SARS when bats infected captive civets in a live-animal market with the virus. Most profoundly, hunting chimpanzees in Cameroon brought humans HIV about a century ago, most likely by way of an accident in handling an infected carcass.
Other recent, emergent viruses have come to us from bats by way of our domestic animals. Hendra and Nipah virus spilled over in 1994 from fruit bats, by way of horses and pigs in 1999, respectively. In 2012 the MERS virus jumped to humans from camels, which were originally infected from bats several hundred years ago. Caring for our horses’ and camels’ runny noses was responsible for bringing us Hendra and MERS.
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