One of the first questions with any pandemic is the origin of the disease. The most popular theory is that they originated in the wet markets in Wuhan but there are other theories that the virus originated in a laboratory to more nationalist conspiracy theories that its a bioweapon. Scientists around the world have condemned the conspiracy theory talk but there are disagreements on where it started. The most common theory is that it started in the wet markets of Wuhan, where it came from bat-tainted pangolin meat.
While it is likely that the disease came from bats, the specifics can get tricky and experts say anyone who claims to know the source of Covid-19 is guessing.
As far as the wet market theory goes, it's "the most simple, obvious and likely explanation," said Dr. Simon Anthony, a professor at the public health grad school of Columbia University and a key member of PREDICT, a federally funded global program investigating viruses in animal hosts with pandemic potential. PREDICT has discovered 180 coronaviruses over a decade. Wet markets seem like an obvious culprit, but the doubters point to earlier studies which shows that the first patients didn't have contact with the wet markets.
Another popular theory, which was put forward by two Chinese scientists and amplified by right wing pundit Tucker Carleson, is that the virus spread due to mishandling at a nearby lab that does studies on bats. Most of the experts interviewed for this story discounted the theory -- whose progenitors reportedly withdrew their paper -- saying it wasn't supported by evidence.
"We're very confident that the origin of Covid-19 is in bats," said Peter Daszak, president of EcoHealth Alliance, a health nonprofit that tracks zoonotic (meaning animal-to-human transfer) spillover. "We just don't know where exactly it originated -- which bat species exactly. And we don't know how many others there are out there that could emerge in the future."
"The first time you go into China as a Westerner, it is a bit of shock to go to a wildlife market and see this huge diversity of animals live in cages on top of each other with a pile of guts that have been pulled out of an animal and thrown on the floor," he said. "As you walk towards the stalls, you slip on the feces and blood. These are perfect places for viruses to spread. Not only that, people are working there ... kids are playing there. Families almost live there."
One expert, a chemical biology professor and bioweapons expert at Rutgers University, didn't discount the theory.
"The possibility that the virus entered humans through a laboratory accident cannot and should not be dismissed," Dr. Richard Ebright told CNN in an email Sunday.
While Ebright said he did not believe the genome sequence of the virus shows any "signatures of human manipulation," he said there is a risk that a lab worker could have accidentally been infected.
"Lab accidents do happen, we know that, but ... there's certainly no evidence to support that theory," Dr. Simon Anthony said.
"If there was a so-called intermediate host, an animal that the bat virus got into and then allowed it to get into people, the virus might still be in that host," said Daszak, the virus hunter working in China. "And there are hundreds, thousands of these animals and farms and maybe the virus is still there. So even if we get rid of the outbreak, there's still a chance that that virus could then re-emerge and we need to find that out quickly."