A series of unlikely things led to the current pandemic. Most probably, the SARS-CoV2 virus (the virus that causes COVID-19) lived among bats without causing them illness.
These bats shed the virus (viruses are often shed intermittently by their hosts) while in contact with an intermediate host animal that was capable of being infected.
It then had to reach a human via contact with bodily fluids or meat to make the jump into people.
Finally, it had to undergo efficient human-to-human spread. Fostered by international travel, COVID-19 has spread globally and here we are.
Many studies have indicated that the next major infectious disease was likely to arise from wild animals. One of these estimates that more than 75 percent of emerging infectious diseases arise from zoonotic transmission, meaning they jump from animals to people.
Along with COVID-19, examples of emerging zoonotic viruses include Ebola, MERS, and SARS.
In particular, bats and rodents are considered highly likely to host potentially zoonotic viruses. Further, these studies have identified areas with high biodiversity as potential disease hotspots.
It really should have been no surprise that a virus emerged in Asia; scientists have been predicting this for decades. In fact, if you had polled a group of scientists to come up with the most likely scenario for a pandemic virus to emerge, their response would have been basically what happened.
Evidence to date suggests that the COVID-19 virus originated in the Huanan Seafood Wholesale Market, a wet market in Wuhan, China. As with the coronavirus that caused SARS, the COVID-19 virus likely crossed from a bat host to another animal species before making the leap to infecting humans. But it seems as though there was a missed opportunity to discover the exact origins of this virus.
The wet market was shut down and apparently no animals were tested for the virus. While the exact source may forever remain a mystery, the genetic sequencing suggests that it is closely related to the coronavirus that caused SARS. Indeed, researchers had previously identified coronaviruses in horseshoe bats from the region that are more than 80 percent similar.
This global pandemic is the largest public health disaster in modern times, but it didn’t have to be this way. The COVID-19 and SARS viruses are kissing cousins and likely arose from very similar events. The 2003 SARS outbreak was a dress-rehearsal and the global community missed the opportunity to meaningfully change the circumstances that led to its creation. Dangerous practices that bring wild animals into close contact with other species and humans continued.
The wildlife wet markets in Asia re-opened, fostering the rampant wildlife trade that included the sale of endangered species. These markets mix a boggling array of species, but also create situations where live animals are crowded and highly stressed. Stress leads to increased virus shedding, thus amplifying the chances another species will get infected.
Animal species that otherwise would never have met are suddenly in close contact. And this commerce requires that the animals are captured live, handled, slaughtered and eventually consumed, all of which presents the chance of a virus to infect a person.
Treating wild animals like this poses an unacceptable risk to human health, not to mention to the animals themselves with deplorable welfare in these situations.
It is very different from markets that sell domestic animals, where humans have interacted with these species for millennia and we are more accustomed to their various pathogens. Domestic species do still have a risk of pathogen transmission but with the exception of influenza, these are unlikely to cause a pandemic.
Ultimately, this is nature’s way of biting back. There needs to be a co-ordinated international effort to stop the illegal wildlife trade, eliminate wild animal sales in wet markets and protect areas of high biodiversity from encroachment and destruction.
What is more frightening is that things could have been worse. While the COVID-19 coronavirus is more contagious than the one that caused SARS, it is less contagious than the virus that causes measles. Coronaviruses are prone to genetic mistakes, creating wide diversity in the species and the potential to evolve for more rapid human-to-human transmission and more deadly outcomes.
We should consider ourselves lucky that this hasn’t transpired and act now to prevent the next pandemic.
Dr. Jamie Rothenburger, DVM, MVetSc,PhD, DACVP, is a veterinarian who practices pathology and is an assistant professor at the University of Calgary’s Faculty of Veterinary Medicine. Twitter: @JRothenburger