How did the novel coronavirus emerge?

Scientists have been studying how and when this coronavirus first infected humans. We may never know the precise series of events that led to this pandemic. But after studying the virus’s genetic material (aka its RNA), we have a pretty clear idea of where it comes from.


This coronavirus is most closely related to bat coronaviruses, and it evolved naturally in the environment; it was not made in a lab. At some point, the virus likely changed by inserting genetic material from other coronaviruses into its own—a process called recombination. For this virus, recombination likely happened when two different coronaviruses infected the same, currently unknown animal (probably a bat or pangolin) at the same time.  


It looks like this coronavirus experienced recombination specifically in its spike protein region. The spike protein is the part of the virus that allows it to bind to human cells and infect us. And this novel human coronavirus’s spike protein likely came from two different lines of bat coronaviruses and pangolin coronaviruses. Changes in the spike protein are thought to help explain why this virus is so effective at spreading from person to person. 


Zoonotic infections are diseases—like this one—that are caused by viruses that are first found in animals but then “jump” into human populations. Here, we know that bats and (probably) pangolins were involved, but why did this virus emerge in China? 


In general, zoonotic diseases are more likely to emerge in tropical and near-tropical regions, including areas of South and Central America, Sub-Saharan Africa, the Middle East, Southeast Asia, and the Indian Subcontinent. This is because these regions tend to have dense populations very close to rural areas, fast-growing populations, and high food demand that includes wild meats and produce. Together, these factors increase contact between people and wildlife. For instance, places like “wet” markets—where live wild animals are in close proximity to each other and humans—can elevate the risk that zoonotic diseases will emerge. 


So here, contacts between humans, bats, and (probably) pangolins made it possible for this zoonotic disease to infect people first in China. But events like these could occur in any country or region where conditions are favorable for emerging zoonotic diseases.  Outbreaks of zoonotic diseases even occur here in the US, such as the occasional outbreak of swine influenza.  


We study viruses’ genetics to better understand their origins, to improve how we track their transmission, and to inform the design of vaccines and treatments. We have yet to see the full extent of the novel coronavirus’s spread, but the more we know about how this pandemic started, the better prepared we’ll be for the next zoonotic bug.


Last update: July 1, 2020, 4:30 pm ET

Science review: JSS, ERS