Where Did This Coronavirus Come From? An Update.

On 5/21 I posted a blog, “Where Did This Coronavirus Come From?” This post is to update some of that information. However, the conclusion remains the same, we do not know.

In very early January, Chinese authorities took hundreds of samples from animals and from the Wuhan market. As I reported, they found several samples of the virus in drains and sewers in and around the market, but they had inexplicably refused to release the results of animal testing. The Chinese authorities have now confirmed that no animal samples from the market were infected. This suggests that a single person brought a virus that was already adept at human transmission to the market and infected others. This just confirms what was already known; the virus passed through the market, but this says little about where it originated. It, however, does, increase the doubt that it came from an animal in the market.

Recent work published in March by Andrew Rambaut of Edinburgh University, analyzing viral genomic sequences, calculates that the most recent common ancestor of the virus infected someone in late November or early December, though that comes with a “confidence range” stretching back into October. So it presumably fine-tuned its ability to infect humans sometime before this and likely somewhere other than the market in Wuhan, since Wuhan is not a home for the bat species that carries the ancestor virus.

The closest animal version of the virus remains a bat sample collected by scientists in 2013 a thousand miles away in Yunnan. A new paper by two scientists from the Agharkar Research Institute in Pune, India, show that it is the same as a published sample that was collected from an abandoned mineshaft in southern Yunnan in 2013, following an outbreak of pneumonia-like illness that killed three miners there the year before.

So what did happen? At present, the evidence points tentatively to a chain of person-to-person infections occurring somewhere outside the city before somebody brought the virus to Wuhan, where the market acted as an amplifier. The first case could have been a rural farmer or possibly a bat researcher collecting samples for virologists. Or it is possible that another animal was involved in some way, with the virus bouncing between a farmer and his animals, or a wildlife smuggler and his poor prey.

As I concluded in my previous article, “It seems clear that the ancestral virus came from a bat, but there is little certainty about what happened after that. At this point, the only thing certain about the virus is its uncertainty.” Except, a bit more data seems to support the notion that the virus originated outside Wuhan. That is speculative at this point, but it seems more possible.