And let's not even begin to think what will happen if there were to be evidence that this was an intentional release.
But don't you think it's important to know this?
The most scary path would be intentional. I can't think of any other aftermath except for WWIII.
More likely result is that most of the world would stop trading with them. Nobody would want to see a Made in China tag on anything. Which would in turn be very bad for the economy in China and lead to unrest.
So the more likely outcome would be civil war in China.