1 December is World AIDS Day, highlighting the fight against this global pandemic. AIDS, or Acquired Immunodeficiency Syndrome, has killed over 39 million people worldwide since 1981, and some 35 million people are currently estimated to be living with the disease.
AIDS is considered a major challenge of modern public health – indeed, World AIDS Day was the first global health day and has been held every year since 1988. Since 2011, the theme has been ‘Getting to Zero’, referring to the World Health Organisation’s joint goals of ‘Zero new HIV infections. Zero deaths from AIDS-related illness. Zero discrimination’.
AIDS is caused by the Human Immunodeficiency Virus (HIV). HIV is a lentivirus, a group of viruses that cause long-term, chronic diseases with long incubation periods. HIV infects cells such as CD4+ cells that are part of the human immune system, reducing their number and rendering the body increasingly susceptible to infection. As a result, other illnesses and cancers, such as tuberculosis or HIV-associated Kaposi’s sarcoma, occur more frequently as the disease progresses.
There are two types of HIV, both of which are thought to have spread to humans from monkeys and apes. They are mutations of the Simian Immunodeficiency Virus (SIV), which has existed for over 30,000 years. Two strains of SIV that infect chimpanzees and sooty mangabeys, respectively, mutated to infect humans in the early 20th century; these mutations are known as HIV subtype 1 and 2, respectively. Subtype 1 is by far the more widespread and virulent, although many HIV tests also test for subtype 2.
The initial stage of HIV infection is called acute retroviral syndrome. It tends to occur in the first few weeks after infection and usually involves flu-like symptoms. As the infection progresses, common signs include swollen lymph nodes, weight loss and frequent fevers or diarrhoea. The most advanced stage of HIV infection is known as AIDS; at this stage, severe diseases such as tuberculosis and meningitis become increasingly likely and life expectancy decreases rapidly.
HIV can be transmitted via sexual contact, exposure to infected blood, or from mother to child during pregnancy, birth or breastfeeding. Other bodily fluids such as saliva, sweat, tears or vomit cannot cause infection unless they are contaminated with blood.
The most frequent mode of HIV transmission is through unprotected sex with an infected person. Worldwide, the majority of infections occur as a result of heterosexual contact, although men who have sex with men (MSM) tend to be proportionally more at risk in high-income countries. For example, nearly two thirds of new HIV infections in the USA in 2009 were in MSM.
Blood-borne infection can result from needle-sharing for intravenous drug use and injections or blood transfusions with unsterilised equipment. Transfusions of infected blood are a particularly important risk factor, with over 90% of such transfusions resulting in the recipient contracting HIV.
Transmission from mother to child is the least common of the three main modes of transmission. However, it accounts for 9 of every 10 HIV cases in children.
There is currently no known cure or vaccine for AIDS. Depending on how early the disease is diagnosed, it can be managed with a ‘cocktail’ of drugs called antiretrovirals. These can slow down the progression of the disease to final-stage AIDS and lower the risk of death. They also lower the risk of common HIV-related infections such as tuberculosis and can improve mental and physical well-being.
If antiretroviral drugs are used soon after infection with HIV, patient life expectancies near the national average are possible. This is a significant improvement over the average post-infection survival time for those not taking antiretrovirals, which is estimated to be around 11 years.
Nearly 12 million people were receiving antiretroviral cocktails in low- and middle-income countries in 2013; 750,000 of them children. The treatment of children is lagging behind, with 24% of HIV-positive children receiving treatment compared to 38% of adults.
Condoms are the main weapon in the fight against AIDS, reducing the likelihood of HIV transmission to below 1% per year. Other measures such as spermicides, gels and male circumcision have been reported to reduce transmission rates in sub-Saharan Africa, but condoms – along with large-scale education and counselling programmes – remain by far the dominant measure to stop the HIV pandemic.
Antiretroviral treatment can effectively prevent the transmission of HIV. It can be used as a preventative measure by an infected person, reducing the likelihood of sexual transmission by up to 96%, or by non-infected people to minimise their risk of contracting the virus. Non-infected people can also receive treatment immediately after suspected exposure to HIV.
The risk of HIV being transmitted from mother to child can be minimised – but not eliminated – if the mother receives antiretroviral drugs during pregnancy and her baby receives them in the first 18 months after birth. Over two thirds of HIV-positive mothers and their babies now receive antiviral treatment in low- and middle-income countries, and this statistic is steadily rising.
As of 2013, new HIV infections have declined by a third since 2001 – in children, they have declined by more than half. The availability and cost of antiretroviral therapy in low- and middle-income countries has improved considerably, and the number of AIDS-related deaths has dropped accordingly. These statistics justify the WHO’s ‘Closing the Gap’ theme, a contrast to earlier themes such as ‘Children Living in a World with AIDS’ or ‘I Care. Do You?’.
Each year, the White House commemorates World AIDS Day by hanging a ribbon outside the building. This became the first such symbol to decorate the building since Abraham Lincoln’s times. It is thanks to the work of countless people around the world that we are making progress in the fight against AIDS, giving hope to the millions of people living with HIV.