Aids: 20 years on

High profile campaigns have failed to stem HIV cases

Tuesday marks the 20th anniversary of the day when health officials in the US first publicly recognised Aids as a potential public health problem.

The anniversary has already been marked with vigils and marches in the US.

BBC News Online's Martin Hutchinson reports on the history of a disease that poses a bigger threat than ever to mankind.

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Aids kills millions worldwide each year and in some countries is the leading cause of premature death.

Even in developed countries, the threat is ever present - the UK has just announced that the number of HIV infections is growing at the fastest rate yet.

A spokesman for the Terrence Higgins Trust, the UK Aids charity that marks its 20th anniversity next year, said: "There is no other recorded example of a disease growing from nothing to take 20m lives in just 20 years.

"Only a vaccine can provide the necessary protection worldwide and halt this increase."

However, despite a huge amount of money spent on research, a vaccine for the virus is still some distance away.

Spotting the problem

In 1981, a sharp-eyed technician at the US Centers for Disease Control was the first to spot something untoward happening to the health of gay men in the US.

There were a high number of requests for drugs to treat a type of pneumonia called PCP.

PCP, along with a cancer called Kaposi's Sarcoma, both normally extremely rare conditions, were occurring more often than expected among gay populations in Los Angeles and New York.

At first some sort of drug abuse was thought to be the cause - but it soon became clear that some sort of infectious agent was to blame.

Aids facts

30 million people worldwide have HIV

21 million people have died of Aids, mostly in Africa and Asia

15,000 people worldwide are infected by Aids daily

The following year the syndrome was eventually called Acquired Immune Deficiency Syndrome.

While many cases were among gay men, others were vulnerable, the scientists found, particularly injecting drug users. Heterosexual transmission was also possible, they found.

The link between a particular virus and Aids was found by doctors at the Institute Pasteur in France in 1983.

The following year, gay bathhouses in San Francisco were shut in an attempt to restrict transmission in that community.

However, US officials were still upbeat about eradication of the illness, with some predicting the arrival of vaccines within just a few years.

Origin of Aids

The origin of Aids is still controversial today - a minority of doctors remain unconvinced that getting HIV leads to the development of Aids.

Those who do blame HIV have uncovered some evidence that it is closely related to viruses present in some species of monkey found in central or western Africa.

It is believed that these simian viruses could have jumped the species barrier when infected monkey tissue was eaten by humans.

Some scientists think that monkey kidney cells, used to grow up stocks of polio virus vaccine in the 1950s may have been a source of contamination, although other evidence contradicts this.

Although the first recognised case happened in 1981 in the US, analysis of older tissue samples have revealed viral traces much earlier.

One, taken from a man in what is now the Democratic Republic of Congo, revealed the presence of HIV as early as 1959.

One man, Gaetan Dugas, has been given the tag of "patient zero", and is credited by some as the source of the HIV epidemic in the US from the 1980s onwards.

Dugas, an airline steward, had travelled to Africa and was a common link to many of the early cases of Aids.

He died from the disease in 1984.

Worldwide spread

While the disease was first noticed by the rigorous surveillance systems in the US, by 1985 it was clear that Aids was a common illness in other countries.

By 1990, some 9m were estimated worldwide as having HIV, 5.5m in Africa.

This number has grown enormously in countries where access to methods of safe sex are unreliable, or where injecting drug use is more common.

In 2000 there were an estimated 3m Aids deaths worldwide - 2.4m in Africa.

There is even evidence in some regions that the disease numbers are falling away because whole age groups most likely to get the disease have been devastated.

The burden is expected to shift to other regions, such as Asia, in the coming years.