【明報專訊】Since 1988, United Nation member states have been observing World AIDS Day (世界愛滋病日) on the first of December. The incurable disease remains one of the global challenges despite the advancement in medical science of our era.

1. History of AIDS

Human immunodeficiency virus (HIV) infection and acquired immune deficiency syndrome (AIDS) originated in non-human primates (靈長目動物) in Sub-Saharan Africa (撒哈拉南非洲). Scientists believe that human infection first occurred in the first half of the last century as a result of people hunting and eating chimpanzees (黑猩猩).

1981 was an important year for the recognition of AIDS. On June 5 that year, the US Centres for Disease Control and Prevention (CDC, 美國疾病控制與預防中心) published a report describing cases of a rare lung infection, pneumocystis carinii pneumonia (PCP), in five young, previously healthy, homosexual men in Los Angeles. By year-end a total of 270 cases of severe immune deficiency among gay men were reported, and 121 of the victims had died. The CDC began to use the term "AIDS" the next year.

Today AIDS remains a pandemic (流行病). According to figures from the United Nations, 35.3 million people lived with HIV in 2012. Known as HIV carriers (病原攜帶者), people who live with HIV are not necessarily AIDS patients. An HIV carrier will become one only after he has developed AIDS-defining conditions such as tuberculosis (結核病).

The first case of HIV infection in Hong Kong was identified thirty years ago. According to statistics from the Department of Health (衛生署), 6,646 HIV cases had been logged here and 1,497 of them had become AIDS patients as of 30 June 2014.

2. Why AIDS remains a global problem

HIV is transmitted through body fluids such as blood, semen (精液), pre-seminal fluid, rectal (直腸) fluids, vaginal (陰道的) fluids and breast milk. Sexual intercourse, the sharing of needles and blood transfusion are the main ways by which HIV is spread.

There are a number of reasons why AIDS remains a global challenge. First, HIV is a virus that expands and multiplies using the body's immune system (免疫系統). The immune system works to tackle the virus. However, the more it does so, the more able HIV is to replicate (複製). Second, once in the human body, the virus copies itself very fast. Third, though the primary infection of the virus may come with some strong symptoms (such as fever and fatigue), most HIV carriers do not display any visible symptoms for 8 to 10 years. Unaware that they have contracted the virus, they may continue to have unprotected sex and thus spread HIV to others.

3. What is being done to contain the HIV pandemic?

Efforts are being made to reduce HIV transmission and to help HIV carriers lead better lives. Governments have long been promoting the use of condoms as a way of preventing HIV infection, and sharing of needles is actively discouraged. Other educational efforts are aimed at dispelling myths (like the idea that one may contract AIDS by simply shaking hands with an HIV carrier), thus helping remove the stigma (羞恥感) attached to being HIV-positive. Meanwhile scientists continue to work on better medicines and the development of a vaccine for the disease.