It came from dogs. Its actually a fusion of a canine and feline version. Its a Coronavirus, but its not COVID-19. Classification of viruses can be not really the same as bacteria; they are a "family" of RNA viruses with a distinctive shape, but that doesn't mean they are all actually related to each other. Viruses essentially evolve from "us" (animals), and they are, in effect, a record of all the animals their line has infected. For a virus to replicate (its not reproducing in the sense that life reproduces), it hijacks the cell machinery that replicates DNA or RNA, and it ends up stealing little snippets of RNA/DNA along the way. When viruses get into bats, then this can sometimes be worrisome. Bats, while a mammal, have a unique, almost supercharged immune system, I suspect because of the environment in which they live, in these huge colonies, often in humid, warm conditions.They live essentially constantly infected, constantly generating inflammatory factors, but they aren't killed or sick. Their immune systems essentially train viruses to be very virulent. COVID-19 was one of these. You always want to detect these new infections as early as possible. COVID-19 was first seen in December 2019, but diagnostic tests not developed until Jan-Feb 2020. But it was probably in circulation a lot longer than that. Partly as a result of the Pandemic, we hope there are better tools to spot these "emerging infectious diseases" (EIDs) earlier. The latest Ebola outbreak shows we are not there yet; its a new strain, and the labs were only looking for older strains, and essentially the outbreak went undetected for a while (people were sick, dying, but the lab tests ran said it wasn't Zaire Ebola etc). With the Canine Coronavirus, the reports indicate because cases in humans have now been seen in Haiti and South East Asia, then its likely in global circulation. At least we have tests for it. We don't really know why SARS erupted; the issue is, for equally mysterious reasons, it just disappeared, and with it, any impetus to study it more. MERS is another coronavirus, at one time described as having a 90% fatality rate (might be toned down). Its come from camels, but bats have become involved. Killed mostly old Arabs with camel farms, racing camels in their retirement. So far, the numbers have stayed low. Mass events like the annual Haj haven't caused an explosion of cases (yet). So, is the FIFA World Cup a mass event that could give this virus legs? Maybe. In the run up to the 2008 Beijing Olympics, there was an outbreak of Foot and Mouth Virus, which put 50,000 people in hospital, really unusual. The Chinese were on the ball monitoring visitors, but nothing further happened. COVID19 hit the US in two ways. West coast infections seem to have arisen mostly because of direct contacts with China; in effect, exposure to a wild type, comparatively less serious. East coast, via New York, it was exposure to cases coming from Europe, particularly Italy. Northern Italy has close trade connections to Wuhan, through the textile trade, but also car parts. It looks like a strain had been in circulation, undetected, for a while, a recombination event, and suddenly a distinctly more robust, virulent strain, that caused really serious illness emerged, and then ended up in New York. Going back a long way, Spanish Flu in 1918, killed millions. Where did it come from. It didn't come from Spain. It was first seen in refugee camps in Spain, in 1918, hence the name. We know there were earlier cases in Kansas City, so for a while, epidemiologists reckoned it came from the US, via GIs shipped to Europe for the end of the Great War. But now this has been revised; it likely came from China, where there was a flu outbreak in 1916-177, not a particularly remarkable one. Chinese coolies were recruited to go to France, and traveled across Canada, into Kansas/Missouri, and them picked up trains to East coast ports. It might still have been a "normal" flu at that point, but for the fact it got to Europe just as a war was ending in Winter 1918. Infections occurred among troops in trenches, but it was the hospitals with wounded men that were cleared first, because everyone wanted to go home, but also I guess there was a bit of uncertainty if the war was really over. The virus circulated among relatively fit men, who's bodies fought off the virus, but they probably had repeat infections because of the conditions in the field. Leading to emergence of a virulent strain (we saw the same in COVID-19, the later variants likely came from a cancer patient in Kent, and HIV patients in Botswana. Every pandemic and epidemic in history can be traced to some change in human behaviour. 60% of infectious diseases have crossed the species barrier at sometime, and present in different species very differently. eg Canine Distemper versus Human Measles. Closely related viruses, different diseases.
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