When a friend in London told me he was HIV-positive in the early 1980s, neither of us really knew what it meant. By the time I visited another HIV-positive friend in hospital in New York a decade later, the horror of the Aids pandemic had become apparent. I was shocked by how much his condition had deteriorated in the couple of years since I'd last seen him, when he had been well enough to wander round Manhattan with me.
At the same time, I was touched by the support system for patients, including an organisation which walked my friend's dog daily when he became too frail to do it himself. He died not long afterwards, joining thousands of gay men whose lives were tragically cut short. The prognosis for HIV-positive people has changed dramatically since the 1990s with the development of anti-retroviral drug therapies.
A couple of years ago I watched the harrowing documentary We Were Here about the Aids crisis in San Francisco, and was shocked to see archive footage of the ravaged faces of young men.
The film is a testament to the resilience of the human spirit, but the images already seem to be receding into history. Some organisations are looking forward, somewhat optimistically, to a day when there are no new infections.
That is why today's World Aids Day is so important. The time when Aids was seen as a disease of gay men in affluent countries – and used as an excuse to launch shameful homophobic attacks – is long gone. It still affects people in developed countries, and approximately 100,000 individuals now live with HIV in the UK.
But HIV-Aids has reverted to a depressing norm, becoming a disease of poverty; of the estimated 35 million people living with HIV worldwide, 70 per cent are in sub-Saharan Africa.
Most transmission there occurs within heterosexual relationships, including marriage and commercial sex. Some African countries, including Ghana and Malawi, have made significant progress in tackling Aids. But South Africa has the highest number of people with HIV in the world, with almost one in five of the population infected; among women aged 25 to 29, it is close to one in three.
Last week, a report suggested that a fifth of healthcare facilities surveyed in South Africa face a shortage of drugs to treat HIV and tuberculosis. In rural areas, people often have to travel long distances, only to find there are no drugs available.
Women are much more vulnerable to infection by men than the other way round, while many live in cultures where men refuse to use condoms and domestic violence is common.
The link with inequality is confirmed by startling figures from the US, where African-American women have an HIV prevalence rate nearly four times that of white women.
A disease once associated in the public mind with gay white men has turned, in some parts of the world, into a tragedy for poor black women.