Why did the disease The Black Plague seem to disappear in the winter?

The disease was spread by fleas on rats. During winter both the rats and the fleas became dormant thus there were no fleas to bite people and infect them with the plague.


Heat is a great bacteria breeder.

All the filth on the streets, left rotting in the height of summer would have bred bacteria very rapidly, spring and summer are after all known as breeding seasons.

In winter, most warmblooded creatures hibernate (even we humans tend to like to stay curled up with a cuppa and duvet).

So, not only the rats but the fleas and the bacteria too would have bred less during winter (this also would have given people time to develop a bit more resistance to the disease).