Click on map: New HIV infections in 2007

There have been a lot of developments since AIDS first appeared on the medical radar screens in 1981. Back then, the diagnosis was a death sentence.

A researcher holds test tubes with HIV-infected blood that has separated into white and red blood cells, Feb. 16, 2004, at the laboratory in Hamburg, Germany. (Christof Stache/Associated Press)

But a November 2006 study in the New England Journal of Medicine provides more evidence that life-long antiretroviral therapy has turned HIV/AIDS into a chronic disease rather than a countdown to death.

The study showed that people who take a break from HIV therapy to reduce the side-effects are more than twice as likely to die than those who take a steady course of the drugs.

"Quite unexpectedly, our results show that interrupting therapy increases the risk of serious non-AIDS-related events," Dr. Wafaa El-Sadr, one of the trial's co-chairs, said in a statement. She is a researcher at the Harlem Hospital Center in New York City.

The trial on nearly 5,500 people infected with HIV in 33 countries was stopped early when the advantages of continuing therapy were clear from the preliminary data.

See photographs and read stories from Médecins Sans Frontières patients living with HIV all over the world: In their own words,through their own eyes. (Courtesy MSF)

It's a big leap since 1981, when doctors in New York and Los Angeles noticed that increasing numbers of previously healthy young men were seeking help for symptoms that included severe weight loss, virulent herpes infections, life-threatening lung and brain infections and previously rare cancers. Around the same time, doctors in France, Zaire and Haiti also noticed a similar syndrome in both men and women.

The remarkable thing these patients had in common was that they were dying from infections to which most healthy people were immune. The doctors were puzzled because they could find no obvious cause for this new syndrome. If a line can be drawn in time, then 1981 marks the official beginning of the AIDS epidemic.

The virus that causes AIDS

By 1983 French researchers had isolated a virus that would later be called HIV (human immunodeficiency virus). They and others linked this virus to the development of AIDS (acquired immune deficiency syndrome), but a test for exposure to HIV would not become widely available for several more years.

HIV is unusual in that it infects the very cells of the immune system … called T-cells … that protect us from attack by viruses, bacteria and other bugs. Once a person becomes infected, the immune system mounts a counter-attack by producing massive numbers of T-cells. For a time, the virus appears to be contained. Indeed, on the outside, the average HIV-positive person appears no different from an average healthy person.

Yet inside the body of someone with HIV infection rages a vast war, as billions of viruses and T-cells are created and destroyed in a single day. The body cannot sustain the expenditure forever, and the virus slowly gains the upper hand. After 10 years or more of battle the immune system begins to collapse. At this point, infections that are, at worst, annoying for the average person, turn lethal as AIDS develops. Overwhelmed by wave after wave of infection, the body eventually gives in.

How HIV spreads

Initially considered a mysterious gay plague, researchers now know that HIV is transmitted through unprotected sex, by sharing needles used for injecting drugs, from transfusions of contaminated blood and from breast feeding by infected mothers. HIV has now spread to the point where one per cent of sexually active adults around the globe have the virus.

The situation in Canada

AIDS in Canada

• An estimated 58,000 people had HIV/AIDS in 2006.
• Every two hours, someone in the country becomes infected with HIV.
• Over 27 per cent of infected people don't know they have HIV.
• Women now account for one-fifth of people with HIV/AIDS, up from one-tenth in 1995.

Canada recorded its first case of AIDS in 1982. The Public Health Agency of Canada estimates that by the end of 2005, there were about 58,000 people living with HIV-AIDS. Of those, the agency estimates that 15,000 — or just over 25 per cent — don't know it.

The number of new infections in Canada in 2005 was higher than in 2002, though death rates have fallen as medical advances increase the life expectancy of infected people.

The greatest proportion of new infections continues to be among men having sex with men, at 45 per cent. Women accounted for 27 per cent of new infections and now make up more than 20 per cent of the population of people living with HIV-AIDS. But the rate of infection among aboriginals is growing faster than any other group. They accounted for 9 per cent of new infections in 2005, an overall infection rate that is nearly three times higher than among non-aboriginals.

Although deaths caused by AIDS have fallen since 1996, Health Canada calls the epidemic "severe and deeply troublesome," and says Canadians should not be complacent.

Health Canada says HIV and AIDS in Canada cannot be classified as a single epidemic, and should instead be thought of as an amalgamation of epidemics. Early on, the epidemic primarily involved gay men or those who received tainted blood products.

Today, according to Health Canada, much of the growth in the spread of HIV and AIDS involves intravenous drug use, aboriginals, and women between the ages of 15 and 29.