A mysterious disease

In the spring of 1979 the Centers for Disease Control in the United States received reports of an unknown disease that affected young men and produced a wide range of symptoms, including rare forms of cancer. In 1981 the disease was named Acquired Immune Deficiency Syndrome (AIDS). It was recognized that transmission of this disease was largely sexual, but it was not until 1983 that the infectious agent – Human Immunodeficiency Virus (HIV) – was “simultaneously” identified by labs in France and the US (the sordid story of this inter-continental competition has been the subject of multiple books). Since the first cases were identified, 20 million people have died from AIDS worldwide.

• The neutral theory of evolution

• Substitution rates

• KA/KS: quantifying the amount of selection on a sequence

At present there is no known cure for this disease and no effective vaccine against HIV infection. Large parts of the world are now facing an AIDS epidemic, with some African nations counting more than 60% of their population among the affected. Although methods exist to keep the virus in check, the high cost of these treatments means that most infected individuals in the developing world will die from AIDS. Indeed, this disease has now surpassed malaria as the number one killer in Africa.

Various aspects of the AIDS epidemic have caught scientists by surprise, including its sudden appearance, mysterious origin, and the difficulty in finding a cure or vaccine.