Because of how outbreaks and pandemics normally progress. Essentially they run like a video game with horrible lag - you don't really see the results of what y

Because of how outbreaks and pandemics normally progress. Essentially they run like a video game with horrible lag - you don't really see the results of what you do to contain them until one or more incubation periods for the disease have passed. The first major action taken by the Chinese government was to quarantine Wuhan. Prior to that, people were traveling freely to other places for the lunar holiday. We're about to reach the end of the incubation period (by the 6th) for people who were infected prior to the quarantine being established. That means if the quarantine of Wuhan contained the outbreak (it's looking less and less likely that it did) we should see some change in the rate of infection in China. That's going to be difficult because of the Chinese government. The flip side of the incubation period ending is that after that point, all new cases should be from people traveling who infected other people. So far, almost all the people who are in quarantine world wide were physically in Wuhan. We don't know yet how many people who have been infected by travelers there are because we haven't hit the end of the post-quarantine incubation period. At present, there could be people all over the world who are infected, don't have symptoms or only mild symptoms, are contagious and spreading the disease, and who won't be discovered as carriers for another week. This week is going to be telling... we may suddenly see a massive uptick in infected outside China (and outside quarantines elsewhere), and if we do it's likely that it's too late to contain the virus, all we can do is limit its spread somewhat and treat the infected.. world wide. If it's really out of containment, given its apparent level of contagiousness it's likely that eventually a significant percentage of all humans alive right now will catch it, and that 2-3% of those people will die - quite possibly a lot more since the numbers of infected are going to overwhelm health care systems worldwide... too many people won't get treated even in western countries. In the third world, in places where people are packed together in slums and large cities, it'll be far worse. For your consideration, if the virus only spreads through China and India, and if e.g. 20% of the people become infected, that means something like 13.6 million people could die, and the rest of us will be dealing with the impact to health care systems, reduced food production, lost wages, reduced military strength and attendant weaknesses in defense, and a host of other problems. So... this virus is rather concerning, not because it kills lots of people (although it can) but because we likely can't control it, and even the number of people it will kill is far too many, and the rest of us are going to be dealing with the consequences for years.