HIV is spread by bodily fluids such as blood, breast milk or semen. It gradually weakens the body’s immune system and makes it vulnerable to disease, including ones rarely seen in otherwise healthy people. The surprising emergence of such cases in the 1980s is what tipped off health experts to what became known as the AIDS epidemic.

The United Nations AIDS agency has warned that more than 6 million lives could be at risk over the next four years if the US government cuts off global funding of HIV/AIDS programmes.