Tinderbox: How the West Sparked the AIDS Epidemic and How the World Can Finally Overcome It, attempts to pinpoint the birth and early life of HIV and AIDS.
Considering a wealth of evidence, the authors suggest that the European Scramble for Africa during the late 19th and early 20th century helped turn localised outbreaks of the infection into a global epidemic.
Read more: http://www.dailymail.co.uk/health/article-2107605/HIV-epidemic-driven-colonialism-Africa-century-ago.html#ixzz1nhlAqwEM
I suppose if you build roads and cities, people will use the roads to get to the cities - and bring whatever they have with them. Including viruses.