Acquired immunodefi ciency syndrome

In the 25 years since the fi rst reported cases of acquired immunodefi ciency syndrome (AIDS), more than 70 million people have been infected with the human immunodefi ciency virus (HIV). HIV is a retrovirus that is spread from mother to child, through blood contamination and through sex. Antiretroviral drugs administered to HIV-infected pregnant women and the newborn child, together with exclusive or no breastfeeding, have drastically reduced mother-tochild transmission. Screening of blood supplies, universal safety precautions in medical settings, and needle exchange programmes for intravenous drug users are effective in avoiding bloodborne spread. Reduction in sexual transmission is achievable through sexual abstinence, monogamy, condoms, treatment of concurrent sexually transmitted infections, male circumcision, and HIV counselling and testing. When spread, HIV specifi cally infects and replicates in CD4+ cells, leading to the systematic destruction of CD4+ cells over a period of years. The drop in CD4+ T-cell numbers to low levels leads to individuals developing symptoms including weight loss, low-grade fevers, night sweats, frequent fungal infections, and eventually various opportunistic infections and malignancies, which signal the onset of AIDS. Until then, individuals who have been asymptomatic with HIV infection over several years have been infectious, thereby creating the conditions for the effi cient spread of this virus. HIV infection is readily diagnosed by assays detecting antibodies, viral components, and the viral genome. More than 25 antiretroviral drugs are known to be effective against HIV. Combinations of these drugs, referred to as highly active antiretroviral therapy, are effective in treating HIV infection. Globally, it has proven to be a substantial challenge to extend HIV prevention programmes and provide treatment to those who most need it, as a disproportionately large burden of this disease is in poor countries. This pandemic has created many ethical, social, human rights, and political challenges. The estimated 25 million people that have already died from AIDS far exceeds the total killed in all the major wars of the twentieth century. AIDS is the world’s most devastating epidemic and the deadliest in the history of humankind. Acquired immunodefi ciency syndrome