Host to Host to Host
The emergence of a new coronavirus in Wuhan at the end of 2019 has not been a virological surprise. New coronaviruses causing respiratory infections have been detected from time to time since SARS (which was a surprise) in 2002-3; MERS came in 2012. How ‘new’ these viruses are is debatable. Some may be novel in the sense that they evolved when two or more different virus strains swapped their genes (recombination). Others may have acquired novel properties as they moved from one natural host through a second to a third. SARS probably came from a bat that infected a civet cat, then becoming a virus that could infect humans. Maybe this kind of transfer from host to host to host happened in Wuhan last year. Coronaviruses are generally quite fussy about the kind of animal they infect. Different ones cause diseases in chickens, turkeys, pigs, cattle, cats, ferrets, rabbits and mice, and cause a significant minority of colds in humans, but they tend to stick to these hosts when they infect them.
Information about the new Wuhan virus is still relatively sparse. But it has only been under investigation for less than a month. So far it seems to be more like influenza than SARS, which was nasty because it caused significant damage deep in the lungs. The Wuhan virus’s genome has been sequenced, confirming that it is related to, but different from, SARS, and making it possible to develop accurate laboratory tests. Draconian measures curtailing travel have been taken in Wuhan in an attempt to stop the virus getting established in other parts of China. The hope is that the virus will fizzle out. It’s too early to tell – but SARS did.