Acquired Immune Deficiency Syndrome (AIDS)

Professional Reference articles are written by UK doctors and are based on research evidence, UK and European Guidelines. They are designed for health professionals to use, so you may find the language more technical than the condition leaflets.

See also: HIV and AIDS written for patients

The human immunodeficiency virus (HIV) which causes acquired immune deficiency syndrome (AIDS) has brought about a global epidemic of massive proportions. HIV is a retrovirus and also the term often applied to the infection before the deterioration of the immune system to produce a full-blown picture of AIDS.


It has become a massive problem and according to the World Health Organization (WHO) in 2012:[1]

  • An estimated 33.4 million people are living with HIV worldwide. 2008 figures were 33.4 million.
  • There were 2.3 million newly infected people in 2008. 2008 figures were 2.7 million.
  • 1.6 million people died of AIDS in 2012. 2008 figures were 2.0 million.

Poor record keeping and returns from some countries make these figures unreliable.

In Africa antiretroviral treatment coverage has increased significantly. This has partly been due to the Treatment 2015 initiative which aims to ensure that the world reaches its 2015 HIV treatment target of 15 million. In sub-Saharan Africa:[1]

  • In 2008, 2,120,000 people were receiving treatment - 30% of the total number needing it. In 2012, this figure had risen to 7.6 million. Because the WHO expanded its criteria for people who would benefit from antiretroviral therapy, this still only equates to 25% of the population who needs it.
  • The percentage of pregnant women receiving antiretrovirals for preventing mother-to-child transmission of HIV increased from 45% in 2008 to 65% in 2012. Due to the Prevention of Mother-to-Child Transmission (PMCT) initiative, some countries have reported even higher percentages.[2]
  • Only 45% of people aged 15-49 living with HIV know their HIV status.[3]
  • As of 2011, over 15 million children had lost one or both parents due to AIDS.[4]

Notable progress has been made to the extent that it could be said that the end of the AIDS epidemic is in sight. In many parts of Africa the prevalence appears to be getting stable. This means that the number of people dying from the disease is roughly equal to the number of new cases. However, whilst new HIV infections have dropped by 38% globally since 2001, 2.1 million people were newly infected in 2013. There are also 22 million people who are not accessing life-saving treatment. Access to AIDS services are still patchy due to such issues as geography, gender and socio-economic factors.[3]

United Kingdom[5]

According to a report from Public Health England (PHE), there were an estimated 100,000 adults aged 15-59 living with HIV in the UK in 2012, 22% of whom were unaware of their infection. The number of deaths among HIV-infected people has continued to decline since the introduction of antiretroviral therapy and a total of 490 people infected with HIV were reported to have died in 2012. There were 6,360 new diagnoses in 2012 in the UK. New diagnoses in men who have sex with men (MSM) continue to rise. This reflects both an ongoing high level of transmission and an increase in the number of men coming forward for testing.

PHE receives information on HIV infections from several sources. The major sources of information are reports from clinicians and laboratories of newly diagnosed infections, an annual survey of all patients seen for HIV-related treatment or care and a family of unlinked anonymous surveys which tests blood samples taken for other investigations, after they have been irreversibly unlinked from any patient identifiers. All reporting methods are confidential and avoid the use of names.

AIDS is currently defined as an illness characterised by the development of one or more AIDS-indicating conditions. It is diagnosed in people infected with HIV when they develop certain opportunistic infections or malignancies for the first time. The following list relates to diagnosis in adults. Congenital HIV and Childhood AIDS has its own separate article.

AIDS-defining conditions in adults
Candidiasis of bronchi, trachea or lungs.Lymphoma, Burkitt's (or equivalent term).
Candidiasis, oesophageal.Lymphoma, immunoblastic (or equivalent term).
Cervical carcinoma, invasive.Lymphoma, primary, of brain.
Coccidioidomycosis, disseminated or extrapulmonary.Mycobacterium avium complex (MAC) or M. kansasii, disseminated or extrapulmonary.
Cryptococcosis, extrapulmonary.Mycobacterium tuberculosis, any site (pulmonary or extrapulmonary).
Cryptosporidiosis, chronic intestinal (>1 month's duration).Mycobacterium, other species or unidentified species, disseminated or extrapulmonary.
Cytomegalovirus (CMV) disease (other than liver, spleen or nodes).Pneumocystis jirovecii pneumonia.
CMV retinitis (with loss of vision).Pneumonia, recurrent.
Encephalopathy, HIV-related.Progressive multifocal leukoencephalopathy.
Herpes simplex: chronic ulcer(s) (>1 month's duration); or bronchitis, pneumonitis or oesophagitis.Salmonella septicaemia, recurrent.
Histoplasmosis, disseminated or extrapulmonary.Toxoplasmosis of brain.
Isosporiasis, chronic intestinal (>1 month's duration).Wasting syndrome due to HIV.
Kaposi's sarcoma. 

When HIV infection is diagnosed in a routine test, as for blood donation, in pregnancy, or after counselling a person with a lifestyle that puts him or her at risk, there is not usually full AIDS but just infection with HIV. When the disease is suspected, HIV counselling must precede testing. There is a characteristic presentation of the infection that is described in the separate article Primary HIV Infection. Once the diagnosis is made, the separate article Managing HIV-positive Individuals in Primary Care becomes relevant. The separate article HIV and Skin Disorders outlines the many dermatological manifestations of the disease.

Awareness of modes of transmission is very important, as the key to tackling this disease lies less in treating it than in preventing its spread. The relative importance of the various means of transmission varies considerably from country to country and even within countries. The following is derived from UK sources.

Sex between men

51% of infections in the UK in 2012 occurred through sex between men and this group remains at greatest risk.[6]There has been no evidence in recent years of a decline in the numbers of new infections in this group and over 3,250 new diagnoses of HIV occurred in 2012.[5]

Despite generally high levels of awareness of the risks for HIV acquisition, in 2012 an estimated 34% of adults were diagnosed with a CD4 cell count ≤200 per mm3 within three months of diagnosis. The percentage diagnosed with CD4 cell counts ≤350 per mm3 (the threshold at which treatment should be considered according to 2008 British HIV Association guidelines) was 34%.[5]

Estimation of current incidence of HIV is difficult. A back-calculation analysis (a statistical method using incubation period to project future distribution of infection) suggests there has been little change in HIV incidence in MSM over recent years. If there has been a decrease in transmissibility associated with antiretroviral treatment in those diagnosed it may have been offset by an increase in risky behaviours. In 2012, there were 2,300-2,500 new infections annually and 7,200 MSM undiagnosed.[5]London has been the main focus of the HIV epidemic in the UK. Of those MSM receiving HIV care in 2012, 50% lived in London.[7]

This must be a great disappointment to those who have worked hard to educate this group.

Sex between men and women

The number of new cases of AIDS acquired from heterosexual intercourse used to be greater than from men who have sex with men, but this situation was reversed in 2011. Approximately half (52%, 1,560/2,990 in 2011) of all infections among heterosexuals were probably acquired in the UK and this proportion has increased over recent years. The figure in 2002 was 27%.[5]

Black Africans have traditionally been over-represented in this category. However, recent research suggests that up to a fifth of HIV infections among black African men initially classified as 'heterosexual exposure' in the UK are likely to have been acquired as a result of sex with other men.[8]

With the numbers of those who acquired their infections heterosexually there has been an decrease in the number of women diagnosed. The male:female ratio for all new infections diagnosed in 2008 was about 1.6:1 whereas in 2012 it was 2.6:1.[9]

In 2012, 65% of men and 57% of women with heterosexually acquired infection are being diagnosed late with a CD4 count of less than 350 cells/mm3.[5]

In 2012, 29% of MSM newly diagnosed with HIV had a co-existent acute STI (chlamydia, gonorrhoea and/or syphilis), compared to 11% of heterosexual men and 9% of women.[5]

Injecting drug users

The total number of cases of HIV in the UK includes 120 cases from injecting drug use (IDU). IDU has played a smaller part in the HIV epidemic in the UK than it has in many other European countries and the numbers of new diagnoses have been around 100 for the last few years. In 2013, the prevalence in England, Wales and Northern Ireland in recent initiates to injectable drugs was 1.0%. This was similar to previous years, suggesting that this source of infection remained at relatively low levels.[10]

Heterosexual transmission to women from male injectable drug users is at a very low level. Prevalence in the male cohort who acquired infection from shared injection equipment was 0.8% in 2011.[11]

Behavioural changes among injectors and the prompt introduction of harm reduction measures such as needle exchange programmes from the mid-1980s probably prevented many other urban areas in the UK from experiencing the localised epidemics on the scale seen in Scotland. In the UK, sharing rates remain higher than in the mid-1990s with almost one in three injectors in the Unlinked Anonymous survey of injecting drug users reporting direct sharing of needles and syringes in the previous four weeks. The continuing transmission of hepatitis B and hepatitis C in those aged under 25 shows the potential for further HIV spread among injecting drug users.

Mother-to-child transmission[6]

There are separate articles on Congenital HIV and Childhood AIDS and the Management of HIV in Pregnancy and so this section will be shortened.

Antenatal testing and the availability of drugs to reduce mother-to-child transmission has resulted in a mother-to-child transmission rate of just 1%. In 2011, the number of infections resulting from mother-to-child transmission was 95. Increasing numbers of HIV-positive women are becoming pregnant and choosing not to have terminations. It is thought this is due to the increasing availability of drugs to prevent mother-to-child transmission.

Blood products and blood transfusion

Production of the clotting factor concentrates, mainly to treat patients with haemophilia A and haemophilia B (Christmas disease), involves the pooling of very many donations and a single donation could contaminate a batch of concentrate used to treat many patients. There have been no recorded transmissions of HIV by this route in the UK since the introduction of heat inactivation of concentrates and donor screening in 1985.

Around 1,350 people in the UK have been infected through treatment with blood factor concentrates and all but 13 are male. Two thirds have died, 31% of them without AIDS having been reported. People with haemophilia may die from liver disease and haemorrhage before the development of an AIDS-defining condition. Since 1985, all blood donations have been screened for HIV antibody. There have been only two proven incidents of antibody-negative blood infectious for HIV being accepted for transfusion in the UK since then (the donor being in the 'window period' when blood is infectious because of recent HIV infection but too early for antibodies to be reliably detected by the screening antibody test). Most diagnoses from blood transfusions come from areas of the world where screening is unreliable and inconsistent. The last infection acquired from such a source was reported in 2002.

In the UK in 2012, 15 donors tested positive for HIV infection at screening. This represented 0.6 detected infections per 100,000 donations. These were mainly in men who probably acquired the infection via heterosexual transmission.[5]

Investigations for HIV are described in the separate article Human Immunodeficiency Virus (HIV). Further investigations for AIDS-defining conditions may be indicated. Media interventions can improve the uptake of testing but this might not be sustained.[12]

The basis of management is described in the separate article Human Immunideficiency Virus (HIV). There may be defining conditions such as Pneumocystis jirovecii pneumonia that will need treatment. Highly active antiretroviral therapy (HAART) has improved the prognosis enormously in terms of duration of survival but premature death is to be expected.

Treatments with HAART have shown considerable progress since the first antiretroviral was approved for use by the FDA in 1987. Impressive improvements in life expectancy and quality of life have ensued. There are, however, still many problems. Although HAART is able to suppress the viral load in the plasma, it fails to eradicate it,and once HAART is initiated, treatment needs to be continued for life. The side-effects of long-term HAART include lipodystrophy, lactic acidosis, insulin resistance, and hyperlipidaemia.

The number of new infections worldwide continues to rise, particularly in women, and effective drug treatments have not yet reached the vast majority of infected individuals in resource-limited countries.[13]In addition, patients require high adherence to the therapy to achieve viral suppression and prevent the development of a drug-resistant virus. Modern regimes are less onerous than older ones. They are simpler and involve fewer tablets, whereas it used to be necessary to take 16 to 20 tablets a day.

Some people will wish to use herbal remedies and a Cochrane review was able to find a small number of trials, some of which seemed to have adequate methodology.[14] There was no significant clinical benefit and objective criteria such as CD4 count were unaffected. Since the review there have been a few studies in the literature suggesting some benefit from herbal remedies but larger trials are needed.[15, 16]

There may be some value in providing prophylactic treatment. A Cochrane review found some benefit in treating latent tuberculosis.[17] Another review found only one trial that examined the benefit of prophylactic co-trimoxazole in children. It was from Zambia and the result was positive.[18]Prophylactic co-trimoxazole was subsequently endorsed as official WHO policy for exposed infants. However, this guidance has been the subject of controversy and its benefits have been questioned by several subsequent trials.[19]The value of prophylaxis against oropharyngeal candidiasis is uncertain, especially in children. There may be some benefit but at a risk of resistance developing and for poorer countries the cheaper options should be examined.[20]

The impact of AIDS in southern Africa has been devastating. Some communities have been very hard hit with many deaths and economic hardship related to loss of the workforce of young adults. However, significant progress has been made in the last decade. South Africa has the largest antiviral roll-out programme in the world. Campaigns to reduce homophobia are encouraging MSM to declare their sexuality and come forward for testing and treatment. Innovative work with sex workers and injectable drug users, antiretroviral treatment of children, condom distribution programmes and mother-to-child transmission prevention services are all beginning to bear fruit. Life expectancy has increased by five years since the height of the epidemic.[21]With a prevalence of 17.9% and a population of 6.1 million, South Africa has the largest HIV epidemic of any country. In neighbouring countries in southern Africa, the prevalance ranges from 10-15%.[2]

The eradication of AIDS is based on prevention rather than cure: this means education and action. Education promotes the use of barrier contraception and advises against risk-taking behaviour - eg, promiscuity or IDU. However, education can be problematic when a respected body like the Roman Catholic Church appears to dispute the risks. The Church considers that condoms are a sin against nature and that AIDS prevention would be better focused on reducing illicit sex and promoting monogamy. However, there has for some time been a move within the church to differentiate between the use of condoms for contraception and their use for AIDS prevention. There are signs that Pope Francis may introduce a less inflexible approach and is at the time of publication planning a Synod to consider this and other controversial issues.[22]

The use of mother-to-child transmission prevention strategies is another important strand of AIDS prevention programmes. In South Africa, for example, expansion of the strategy has resulted in the mother-to-child transmission rate falling to 3.5%.[21]

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Original Author:
Dr Hayley Willacy
Current Version:
Dr Laurence Knott
Peer Reviewer:
Dr John Cox
Document ID:
1495 (v26)
Last Checked:
19 September 2014
Next Review:
18 September 2019

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