What caused the epidemic to spread so suddenly?

What caused the epidemic to spread so suddenly?

There are a number of factors that may have contributed to the sudden spread of HIV, most of which occurred in the latter half of the twentieth century.

Travel

International travel has undoubtedly played a major role in the spread of HIV.

Both national and international travel undoubtedly had a major role in the initial spread of HIV. In the US, international travel by young men making the most of the gay sexual revolution of the late 70s and early 80s would certainly have played a large part in taking the virus worldwide. In Africa, the virus would probably have been spread along truck routes and between towns and cities within the continent itself. However, it is quite conceivable that some of the early outbreaks in African nations were not started by Africans infected with the 'original' virus at all, but by people visiting from overseas where the epidemic had been growing too. The process of transmission in a global pandemic is simply too complex to blame on any one group or individual.

Much was made in the early years of the epidemic of a so-called 'Patient Zero' who was the basis of a complex "transmission scenario" compiled by Dr. William Darrow and colleagues at the Centre for Disease Control in the US. This epidemiological study showed how 'Patient O' (mistakenly identified in the press as 'Patient Zero') had given HIV to multiple partners, who then in turn transmitted it to others and rapidly spread the virus to locations all over the world. A journalist, Randy Shilts, subsequently wrote a book²³ based on Darrow's findings, which named Patient Zero as a gay Canadian flight attendant called Gaetan Dugas. For several years, Dugas was vilified as a 'mass spreader' of HIV and the original source of the HIV epidemic among gay men. However, four years after the publication of Shilts' article, Dr. Darrow repudiated his study, admitting its methods were flawed and that Shilts' had misrepresented its conclusions.

While Gaetan Dugas was a real person who did eventually die of AIDS, the Patient Zero story was not much more than myth and scaremongering. HIV in the US was to a large degree initially spread by gay men, but this occurred on a huge scale over many years, probably a long time before Dugas even began to travel.