Independent On-line, 26 November 2002, Development and spread of HIV and Aids

London - Aids will have killed 3.1 million people in 2002, five million more were newly infected with the deadly virus and for the first time since the start of the epidemic, half of the 42 million people living with HIV and Aids are women.

Following are some of the key events in the development of the epidemic:

1981 - Outbreaks of two rare illnesses are reported among young homosexual men in the United States. The disorders, a respiratory infection called pneumocystis carinii pneumonia and a cancer, Kaposi's sarcoma, usually infect older men.

1981-1983 - Scientists and researchers start to recognise the emergence of a new disease that destroys the body's immune system, preventing sufferers from fighting simple infections. The illness is also found to affect intravenous drug users and blood transfusion recipients.

1984 - The Human Immunodeficiency Virus, HIV, is identified as the cause of the disease.

- Scientific papers suggesting that Aids is spread through blood are published in The Lancet and the New England Journal of Medicine.

1985 - Scientists develop diagnostic test for the virus.

- First World Aids Conference in Atlanta, Georgia.

1987 - Zidovudine (AZT), the first treatment for HIV, is launched.

1988 - December 1st is designated World Aids Day.

1991 - Videx (ddl), like AZT a member of a class of drugs called reverse transcriptase inhibitors (RTIs), is launched.

1994-1995 - Zerit (d4T) and Epivir (3TC), other RTIs, are launched, increasing the choice of treatments.

1996 - Triple drug cocktails including protease inhibitors that block the replication of HIV in the body are revealed at the 11th World Aids Conference in Vancouver, Canada.

1998 - Scientists image the crystalline structure of the gp120 protein the HIV virus uses to break into the human immune system cells it attacks.

1999 - A chimpanzee named Marilyn helps confirm that the Aids virus first passed into people from chimps; genetic tests show HIV is closely related to a simian immunodeficiency virus or SIV that infects chimps but does not make them sick.

2000 - Five top drug companies agree to slash the price of HIV and AIDS treatments for developing countries, in a breakthrough UN deal.

2002 - The Global Fund to Fight Aids, Tuberculosis and Malaria is set up to fund the fight against the three top infectious diseases.

- In a report showing the epidemic is still in its early stages, the United Nations says that Aids will kill 70 million people over the next 20 years, mostly in Africa, unless rich nations step up their efforts to curb the disease.