The illness AIDS is caused by the Human Immunodeficiency Virus (HIV), which destroys the body’s immune system.
People infected with HIV carry the virus for varying lengths of time before developing AIDS. A small proportion of people develop AIDS more rapidly while many will remain clinically well for 15-20 years.
How HIV leads to AIDS
AIDS occurs when the body’s immune system has been destroyed by HIV. HIV attacks and kills certain white cells in the blood known as T-helper cells. These cells act as messengers within the body’s defence system, warning whenever bacteria and viruses occur so that the body can marshal its defences. As these cells are destroyed by the multiplying virus, people with HIV become much more susceptible to infections and cancers which other people do not get. When the infected person starts to acquire these conditions then AIDS is said to have developed. These conditions are responsible for death among AIDS patients after the immune system has broken down.
Transmission of HIV
Most people catch HIV through unprotected sex (without a condom) with a person who is already infected. Other methods of transmission include direct blood-to-blood contact such as when intravenous drug users share needles. Historically, some infections were caused by transfusions of contaminated blood, although this is increasingly rare as blood is now routinely screened. A woman can pass HIV onto her child either before birth, at birth or even after birth via breast milk. HIV is very fragile outside the body and will die quickly outside the body. For this reason HIV cannot be contracted from someone who is HIV positive through normal daily contact such as shaking hands, drinking from fountains, using telephones or toilet seats.
Symptoms of HIV/AIDS
HIV produces a variety of symptoms as the virus reproduces and the disease progresses. Initial infection can result in no symptoms at all, or a fever similar to glandular fever. The signs of progression to AIDS itself are likely to be tumours, and infections that are recognisable by their infrequency in people with healthy immune systems. Other AIDS-related illnesses include infections, chronic diarrhoea, tuberculosis, and even changes in mental status. The nature of HIV and AIDS means that it leaves patients susceptible to many other diseases.
Preventing HIV infection
During sex, only the use of condoms has been shown to be a partially effective barrier against HIV transmission. The sharing of needles and other equipment among drug users is a major cause of infection which should be avoided. Antiretroviral drugs, caesarean delivery and formula feeding reduce the chance of transmission of HIV from mother to child.