Rise of measles linked with emergence of large cities 2500 years ago | New Scientist
The measles virus crossed over to people from cattle around 500 BC, supporting the idea that it could only get established as a human disease once large enough cities had developed. It s not proof, but it s compatible with the notion that large cities might have provided the opportunity for it to emerge, says Sébastien Calvignac-Spencer at the Robert Koch Institute in Berlin, Germany.
Cities are full of germs. I’ve thought so for a long time.