Kevin de Cock, the head of the WHO's department of HIV/Aids said there will be no generalised epidemic of Aids in the heterosexual population outside Africa.

Dr De Cock, an epidemiologist who has spent much of his career leading the battle against the disease, said understanding of the threat posed by the virus had changed. Whereas once it was seen as a risk to populations everywhere, it was now recognised that, outside sub-Saharan Africa, it was confined to high-risk groups including men who have sex with men, injecting drug users, and sex workers and their clients.

Dr De Cock said: "It is very unlikely there will be a heterosexual epidemic in other countries.