Measles virus was zoonotic in origin, having diverged from the cattle virus that caused a disease called rinderpest. Here’s our punishment (among others) for domesticating bovids: measles got into humans from our cattle and has been with us for roughly two thousand years. Rinderpest has now been eradicated but the measles virus in humans, not. The reason for that, I think, is that it has been easier for us to contain and control bovine behavior than our own.
