> If the markets are like this when there are a few hundred cases in the UK and US, what will they be like when there are tens, or hundreds of thousands of cases and major cities are in lockdown?

Some conservative predictions are arriving at millions of cases in a couple of months. There are too many unknown variables for an accurate prediction but, without really drastic measures, it's difficult to argue with exponential growth.

At some point it will plateau and become another seasonal flu. And we may even get vaccines. But I agree that things are going to become way worse before they improve. Most worrying is the strain on the health care system, which may by itself worse prognosis on other, otherwise unrelated, diseases.