I'm by no means an expert, but what I've managed to figure out so far.

An ordinary paper mask will do very little, you need a respirator type mask. Not one with the huge pieces on the side but one with an active charcoal filter and usually have a small valve on one side. Most come with extra filters, the filters have a lifespan of 48-72 hours.

There are various grades, N95 and N99 being the ones I have seen and can be obtained from Amazon on next day delivery. The prices have increased the last few days.

However, the advice of staying away from livestock and washing hands and face regularly is more important than the mask. I'm off to Vietnam via Shanghai and have bought the masks as a precaution.

I'm sure some others will expand on this.