Quoth the BBC:

“The spread of the Roman Empire through Europe could help explain why those living in its former colonies are more vulnerable to HIV.”

http://news.bbc.co.uk/2/hi/health/7596532.stm

How so?

The claim, by French researchers, is that people once ruled by Rome are less likely to have a gene variant which protects against HIV…

They say that the frequency of the variant corresponds closely with the shifting boundaries of the thousand-year empire.

In countries inside the borders of the empire for longer periods, such as Spain, Italy and Greece, the frequency of the CCR5-delta32 gene, which offers some protection against HIV, is between 0% and 6%.

Countries at the fringe of the empire, such as Germany, and modern England, the rate is between 8% and 11.8%, while in countries never conquered by Rome, the rate is greater than this.

However, the researchers do not believe that the genetic difference is due to Roman soldiers or officials breeding within the local population – history suggests this was not particularly widespread, and that invading and occupying armies could have been drawn not just from Italy but from other parts of the empire.

Instead, they say that the Romans may have introduced an unknown disease to which people with the CCR5-Delta32 variant were particularly susceptible.

A slightly more detailed account of this study can be found on The New Scientist‘s website. 

http://www.newscientist.com/channel/health/mg19926723.900-did-romans-destroy-europes-hiv-shield.html?DCMP=ILC-hmts&nsref=top1_head_Did%20the%20Romans%20destroy%20Europe’s%20HIV%20resistance?

The original article is available only to subscribers.  Here’s the link anyway.

http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6W8B-4T9M645-1&_user=5172862&_coverDate=08%2F27%2F2008&_alid=786208003&_rdoc=1&_fmt=high&_orig=search&_cdi=6650&_sort=d&_docanchor=&view=c&_ct=1&_acct=C000066447&_version=1&_urlVersion=0&_userid=5172862&md5=33d833074730303569023215aaa45a0c