The hysteria starts at the top. Governments must be seen to be 'doing something'......so they do 'something'. Whatever it is, it has to look good so it usually involves what has been seen around the world - lockdowns, quarantines, travel bans etc.
Here in the UK the buzzwords are 'self-isolation'. Sneeze once or have anything that remotely resembles the common cold and you (and your entire family) must 'self-isolate' which means not going out anywhere, at all, anytime, for two weeks. Or possibly longer. Have no contact or interaction of any kind with anybody.
That's why stockpiling is going on - in the absence of sensible government advice/action and the presence of non-info/action and patently flawed info/action, people are assuming that civilisation is going to end (because they themselves aren't thinking and prefer to be led by the nose like brain-dead sheep) and if not end, then at the very least the two week period is a little short so they are working on the basis that this crisis is going to go on for months or more, so they stockpile.
People are also stockpiling because many industries (airlines being a classic example) are very very vulnerable to global disturbance, so people are buying in bulk while they still have the money from a job they think they are going to lose very soon. In fairness, some already have - thanks to governments being seen to 'do something'.
The present problems are primarily due to government stupidity and people stupidity. If you enable panic, panic is what you will get. As we have pointed out already.
Covid-19, or Coronavirus as it is commonly known, is a serious problem. But it requires serious action, which is not easy. And that is the crux of it - governments have - are - taking the easy path and the result is what is being seen in shops and stores around the world.