I’m all for avoiding overreaction, but there are reasonable grounds for considerable concern with this virus. No one has ever tried to contain an outbreak of a respiratory virus by isolating and virtually shutting down entire cities before, and I’m pretty skeptical that it’s possible with probably hundreds of thousands already infected.
The big question is how many asymptomatic infections there are. If there aren’t very many, then containment is more likely but the fatality rate per infection is likely to be uncomfortably high (maybe something like 0.5%), judging from the number of fatalities occurring in diagnosed cases outside mainland China.
On the other hand, if there are lots of asymptomatic infections, then the fatality rate per infection is a lot lower (yay), but the chances of containment are practically zero. And whatever the fatality rate, if containment fails there are likely to be a lot of infected people. I talked to someone in an epidemiology modeling group today, and they said that their current model has 60% of the population becoming infected (barring effective public health intervention, like a vaccine). That is unlikely to be catastrophic but it could be quite unpleasant.
Obviously, the modeling could be wrong for all sorts of reasons – the virus could become attenuated through mutations, there could be innate resistance in a lot of people, whatever. But there are good grounds for public health agencies and researchers to take this very seriously.