[BostonCard]

The phylogenetic tree for SARS-CoV-2 was published a while ago when the initial genome was published:



I believe the issue is that while SARS-CoV-2 (2019-nCoV in the figure above) is similar to a number of bat coronaviridae, my understanding is that there is a key difference at the spike protein that interacts with the human ACE2 receptor.  As a result, though genetically similar, it is not clear that the bat coronaviruses (at least not the ones that are already known) can easily infect humans.

This article provides a good review: https://www.nature.com/articles/s41591-020-0820-9

This is an interesting theory:

https://www.economist.com/science-and-te...yond-china

Jeremy Farrar, the head of the Wellcome Trust, a large medical-research charity, and a former professor of tropical medicine, says his guess is that either sars-cov-2 or something similar to it has been circulating in people in parts of South-East Asia and southern China, probably for many years, and that intermediate hosts have not yet been identified. Dr Farrar spent 18 years working in Vietnam as the head of an Oxford University research unit. He says people go searching for bats for food and sell them in markets in what is a sophisticated trade that can end up in big cities like Wuhan. Bats are able to carry a brobdingnagian diversity of viruses without getting sick, and are also more mobile than people realise. As he puts it, bats “congregate in brobdingnagian colonies, and poo everywhere. And then other mammals live off that poo and then act as a mixing vessel for these sorts of viruses.”

Support for the idea that something resembling sars-cov-2 might have been circulating in the region before the pandemic began also comes from another intriguing observation: the low incidence of covid-19 in South-East Asia, particularly in Vietnam. John Bell, a professor of medicine at the University of Oxford, says everyone thought there would be a flood of cases in Vietnam because the country is right across the border from China. Yet Vietnam has reported only 300 in a population of 100m, and no deaths. The country did not have a great lockdown either, he adds. Nobody could work out what was going on.

One explanation, he suggests, is that Vietnam’s population is not as immunologically “naive” as has been assumed. The circulation of other sars-like viruses could have conferred a generalised immunity to such pathogens. So, if a new one emerged in the region, it was able to take hold in the human population only when it travelled all the way to central China—where people did not have this natural resistance.

This seems a bit speculative to me, but would not be too tough to prove, if serology studies of Vietnamese turned up high titers of antibodies that could potentially SARS-CoV2 way out of proportion to the number of cases and deaths.

BC

[BostonCard]

The phylogenetic tree for SARS-CoV-2 was published a while ago when the initial genome was published:



I believe the issue is that while SARS-CoV-2 (2019-nCoV in the figure above) is similar to a number of bat coronaviridae, my understanding is that there is a key difference at the spike protein that interacts with the human ACE2 receptor.  As a result, though genetically similar, it is not clear that the bat coronaviruses (at least not the ones that are already known) can easily infect humans.

This article provides a good review: https://www.nature.com/articles/s41591-020-0820-9

This is an interesting theory:

https://www.economist.com/science-and-te...yond-china

Jeremy Farrar, the head of the Wellcome Trust, a large medical-research charity, and a former professor of tropical medicine, says his guess is that either sars-cov-2 or something similar to it has been circulating in people in parts of South-East Asia and southern China, probably for many years, and that intermediate hosts have not yet been identified. Dr Farrar spent 18 years working in Vietnam as the head of an Oxford University research unit. He says people go searching for bats for food and sell them in markets in what is a sophisticated trade that can end up in big cities like Wuhan. Bats are able to carry a brobdingnagian diversity of viruses without getting sick, and are also more mobile than people realise. As he puts it, bats “congregate in brobdingnagian colonies, and poo everywhere. And then other mammals live off that poo and then act as a mixing vessel for these sorts of viruses.”

Support for the idea that something resembling sars-cov-2 might have been circulating in the region before the pandemic began also comes from another intriguing observation: the low incidence of covid-19 in South-East Asia, particularly in Vietnam. John Bell, a professor of medicine at the University of Oxford, says everyone thought there would be a flood of cases in Vietnam because the country is right across the border from China. Yet Vietnam has reported only 300 in a population of 100m, and no deaths. The country did not have a great lockdown either, he adds. Nobody could work out what was going on.

One explanation, he suggests, is that Vietnam’s population is not as immunologically “naive” as has been assumed. The circulation of other sars-like viruses could have conferred a generalised immunity to such pathogens. So, if a new one emerged in the region, it was able to take hold in the human population only when it travelled all the way to central China—where people did not have this natural resistance.

This seems a bit speculative to me, but would not be too tough to prove, if serology studies of Vietnamese turned up high titers of antibodies that could potentially SARS-CoV2 way out of proportion to the number of cases and deaths.

BC