AIDS. Or at least that's what French scientists say:
The claim, by French researchers, is that people once ruled by Rome are less likely to have a gene variant which protects against HIV.
This includes England, France, Greece and Spain, New Scientist reports.
Others argue the difference is linked to a far larger event, such as the spread of bubonic plague or smallpox.
In essence, if the claim is to be believed, the Romans were early practitioners of what Jared Diamond would characterize as inadvertent germ warfare. Which brings them full circle, as many historians believe the Empire fell as quickly as it did after the introduction of plagues from outside the Roman world.