{"id":338,"date":"2021-04-19T16:06:23","date_gmt":"2021-04-19T16:06:23","guid":{"rendered":"https:\/\/courses.lumenlearning.com\/suny-hvcc-healthpsychology\/?post_type=chapter&p=338"},"modified":"2021-04-19T16:19:41","modified_gmt":"2021-04-19T16:19:41","slug":"hiv-aids","status":"publish","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/suny-hvcc-healthpsychology\/chapter\/hiv-aids\/","title":{"raw":"HIV\/AIDS","rendered":"HIV\/AIDS"},"content":{"raw":"

Signs and symptoms<\/span><\/h2>\r\n
<\/div>\r\nThere are three main stages of\u00a0HIV<\/a>\u00a0infection: acute infection, clinical latency, and AIDS.[1]<\/a><\/sup>[24]<\/a><\/sup>\r\n

Acute infection<\/span><\/h3>\r\n
\r\n
\r\n\r\n[caption id=\"\" align=\"alignleft\" width=\"280\"]\"A<\/a> Main symptoms of acute HIV infection[\/caption]\r\n\r\n
\r\n
The initial period following the contraction of HIV is called acute HIV, primary HIV or acute retroviral syndrome.<\/span>[24]<\/a><\/sup>[25]<\/a><\/sup>\u00a0Many individuals develop an\u00a0<\/span>influenza-like illness<\/a>\u00a0or a\u00a0<\/span>mononucleosis-like illness<\/a>\u00a02\u20134 weeks after exposure while others have no significant symptoms.<\/span>[26]<\/a><\/sup>[27]<\/a><\/sup>\u00a0Symptoms occur in 40\u201390% of cases and most commonly include\u00a0<\/span>fever<\/a>,\u00a0<\/span>large tender lymph nodes<\/a>,\u00a0<\/span>throat inflammation<\/a>, a\u00a0<\/span>rash<\/a>, headache, tiredness, and\/or sores of the mouth and genitals.<\/span>[25]<\/a><\/sup>[27]<\/a><\/sup>\u00a0The rash, which occurs in 20\u201350% of cases, presents itself on the trunk and is\u00a0<\/span>maculopapular<\/a>, classically.<\/span>[28]<\/a><\/sup>\u00a0Some people also develop\u00a0<\/span>opportunistic infections<\/a>\u00a0at this stage.<\/span>[25]<\/a><\/sup>\u00a0Gastrointestinal symptoms, such as vomiting or\u00a0<\/span>diarrhea<\/a>\u00a0may occur.<\/span>[27]<\/a><\/sup>\u00a0Neurological symptoms of\u00a0<\/span>peripheral neuropathy<\/a>\u00a0or\u00a0<\/span>Guillain\u2013Barr\u00e9 syndrome<\/a>\u00a0also occurs.<\/span>[27]<\/a><\/sup>\u00a0The duration of the symptoms varies, but is usually one or two weeks.<\/span>[27]<\/a><\/sup><\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\nOwing to their\u00a0nonspecific<\/a>\u00a0character, these symptoms are not often\u00a0recognized<\/a>\u00a0as signs of HIV infection. Even cases that do get seen by a family doctor or a hospital are often misdiagnosed as one of the many common\u00a0infectious diseases<\/a>\u00a0with overlapping symptoms. Thus, it is recommended that HIV be considered in people presenting with an\u00a0unexplained fever<\/a>\u00a0who may have risk factors for the infection.[27]<\/a><\/sup>\r\n

Clinical latency<\/span><\/h3>\r\nThe initial symptoms are followed by a stage called clinical latency, asymptomatic HIV, or chronic HIV.[1]<\/a><\/sup>\u00a0Without treatment, this second stage of the\u00a0natural history<\/a>\u00a0of HIV infection can last from about three years[29]<\/a><\/sup>\u00a0to over 20\u00a0years[30]<\/a><\/sup>\u00a0(on average, about eight years).[31]<\/a><\/sup>\u00a0While typically there are few or no symptoms at first, near the end of this stage many people experience fever, weight loss, gastrointestinal problems and muscle pains.[1]<\/a><\/sup>\u00a0Between 50% and 70% of people also develop\u00a0persistent generalized lymphadenopathy<\/a>, characterized by unexplained, non-painful enlargement of more than one group of lymph nodes (other than in the groin) for over three to six months.[24]<\/a><\/sup>\r\n\r\nAlthough most\u00a0HIV-1<\/a>\u00a0infected individuals have a detectable viral load and in the absence of treatment will eventually progress to AIDS, a small proportion (about 5%) retain high levels of CD4+<\/sup>\u00a0T cells (T helper cells<\/a>) without\u00a0antiretroviral therapy<\/a>\u00a0for more than five years.[27]<\/a><\/sup>[32]<\/a><\/sup>\u00a0These individuals are classified as \"HIV controllers\" or\u00a0long-term nonprogressors<\/a>\u00a0(LTNP).[32]<\/a><\/sup>\u00a0Another group consists of those who maintain a low or undetectable viral load without anti-retroviral treatment, known as \"elite controllers\" or \"elite suppressors\". They represent approximately 1 in 300 infected persons.[33]<\/a><\/sup>\r\n

Acquired immunodeficiency syndrome<\/span><\/h3>\r\n
\r\n
\r\n\r\n[caption id=\"\" align=\"alignright\" width=\"280\"]\"A<\/a> Main symptoms of AIDS.[\/caption]\r\n\r\n
Acquired immunodeficiency syndrome (AIDS) is defined as an HIV infection with either a CD4<\/span>+<\/sup>\u00a0T cell count below 200 cells per \u00b5L or the occurrence of specific diseases associated with HIV infection.<\/span>[27]<\/a><\/sup>\u00a0In the absence of specific treatment, around half of people infected with HIV develop AIDS within ten years.<\/span>[27]<\/a><\/sup>\u00a0The most common initial conditions that alert to the presence of AIDS are\u00a0<\/span>pneumocystis pneumonia<\/a>\u00a0(40%),\u00a0<\/span>cachexia<\/a>\u00a0in the form of HIV wasting syndrome (20%), and\u00a0<\/span>esophageal candidiasis<\/a>.<\/span>[27]<\/a><\/sup>\u00a0Other common signs include recurrent\u00a0<\/span>respiratory tract infections<\/a>.<\/span>[27]<\/a><\/sup><\/div>\r\n<\/div>\r\n<\/div>\r\nOpportunistic infections<\/a>\u00a0may be caused by\u00a0bacteria<\/a>,\u00a0viruses<\/a>,\u00a0fungi<\/a>, and\u00a0parasites<\/a>\u00a0that are normally controlled by the immune system.[34]<\/a><\/sup>\u00a0Which infections occur depends partly on what organisms are common in the person's environment.[27]<\/a><\/sup>\u00a0These infections may affect nearly every\u00a0organ system<\/a>.[35]<\/a><\/sup>\r\n\r\nPeople with AIDS have an increased risk of developing various viral-induced cancers, including\u00a0Kaposi's sarcoma<\/a>,\u00a0Burkitt's lymphoma<\/a>,\u00a0primary central nervous system lymphoma<\/a>, and\u00a0cervical cancer<\/a>.[28]<\/a><\/sup>\u00a0Kaposi's sarcoma is the most common cancer, occurring in 10% to 20% of people with HIV.[36]<\/a><\/sup>\u00a0The second-most common cancer is lymphoma, which is the cause of death of nearly 16% of people with AIDS and is the initial sign of AIDS in 3% to 4%.[36]<\/a><\/sup>\u00a0Both these cancers are associated with\u00a0human herpesvirus 8<\/a>\u00a0(HHV-8).[36]<\/a><\/sup>\u00a0Cervical cancer occurs more frequently in those with AIDS because of its association with\u00a0human papillomavirus<\/a>\u00a0(HPV).[36]<\/a><\/sup>\u00a0Conjunctival cancer<\/a>\u00a0(of the layer that lines the inner part of eyelids and the white part of the eye) is also more common in those with HIV.[37]<\/a><\/sup>\r\n\r\nAdditionally, people with AIDS frequently have systemic symptoms such as prolonged fevers,\u00a0sweats<\/a>\u00a0(particularly at night), swollen lymph nodes, chills, weakness, and\u00a0unintended weight loss<\/a>.[38]<\/a><\/sup>\u00a0Diarrhea is another common symptom, present in about 90% of people with AIDS.[39]<\/a><\/sup>\u00a0They can also be affected by diverse psychiatric and neurological symptoms independent of opportunistic infections and cancers.[40]<\/a><\/sup>\r\n

Transmission<\/span><\/h2>\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n
Average per act risk of getting HIV\r\nby exposure route to an infected source<\/caption>\r\n
Exposure route<\/th>\r\nChance of infection<\/th>\r\n<\/tr>\r\n
Blood transfusion<\/th>\r\n90%[41]<\/a><\/sup><\/td>\r\n<\/tr>\r\n
Childbirth\u00a0(to child)<\/small><\/th>\r\n25%[42]<\/a><\/sup>[clarification needed<\/span><\/a><\/i>]<\/sup><\/td>\r\n<\/tr>\r\n
Needle-sharing injection drug use<\/th>\r\n0.67%[43]<\/a><\/sup><\/td>\r\n<\/tr>\r\n
Percutaneous needle stick<\/th>\r\n0.30%[44]<\/a><\/sup><\/td>\r\n<\/tr>\r\n
Receptive anal intercourse*<\/sup><\/th>\r\n0.04\u20133.0%[45]<\/a><\/sup><\/td>\r\n<\/tr>\r\n
Insertive anal intercourse*<\/sup><\/th>\r\n0.03%[46]<\/a><\/sup><\/td>\r\n<\/tr>\r\n
Receptive penile-vaginal intercourse*<\/sup><\/th>\r\n0.05\u20130.30%[45]<\/a><\/sup>[47]<\/a><\/sup><\/td>\r\n<\/tr>\r\n
Insertive penile-vaginal intercourse*<\/sup><\/th>\r\n0.01\u20130.38%[45]<\/a><\/sup>[47]<\/a><\/sup><\/td>\r\n<\/tr>\r\n
Receptive oral intercourse*\u00a7<\/sup><\/th>\r\n0\u20130.04%[45]<\/a><\/sup><\/td>\r\n<\/tr>\r\n
Insertive oral intercourse*\u00a7<\/sup><\/th>\r\n0\u20130.005%[48]<\/a><\/sup><\/td>\r\n<\/tr>\r\n
*<\/sup>\u00a0assuming no condom use\r\n\u00a7<\/sup>\u00a0source refers to oral intercourse\r\nperformed on a man<\/th>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\nHIV is spread by three main routes:\u00a0sexual contact<\/a>, significant exposure to infected body fluids or tissues, and from mother to child during pregnancy, delivery, or breastfeeding (known as\u00a0vertical transmission<\/a>).[13]<\/a><\/sup>\u00a0There is no risk of acquiring HIV if exposed to\u00a0feces<\/a>, nasal secretions, saliva,\u00a0sputum<\/a>, sweat, tears, urine, or vomit unless these are contaminated with blood.[49]<\/a><\/sup>\u00a0It is also possible to be\u00a0co-infected<\/a>\u00a0by more than one strain of HIV\u2014a condition known as\u00a0HIV superinfection<\/a>.[50]<\/a><\/sup>\r\n

Sexual<\/span><\/h3>\r\nThe most frequent mode of transmission of HIV is through sexual contact with an infected person.[13]<\/a><\/sup>\u00a0However, an HIV-positive person who has an undetectable viral load as a result of long-term treatment has effectively no risk of transmitting HIV sexually.[51]<\/a><\/sup>[52]<\/a><\/sup>\u00a0The existence of functionally noncontagious HIV-positive people on antiretroviral therapy was controversially publicized in the 2008\u00a0Swiss Statement<\/a>, and has since become accepted as medically sound.[53]<\/a><\/sup>\r\n\r\nGlobally, the most common mode of HIV transmission is via\u00a0sexual contacts between people of the opposite sex<\/a>;[13]<\/a><\/sup>\u00a0however, the pattern of transmission varies among countries. As of 2017, most HIV transmission in the United States occurred among\u00a0men who had sex with men<\/a>\u00a0(82% of new HIV diagnoses among males aged 13 and older and 70% of total new diagnoses).[54]<\/a><\/sup>[55]<\/a><\/sup>\u00a0In the US, gay and bisexual men aged 13 to 24 accounted for an estimated 92% of new HIV diagnoses among all men in their age group and 27% of new diagnoses among all gay and bisexual men.[56]<\/a><\/sup>\r\n\r\nWith regard to\u00a0unprotected<\/a>\u00a0heterosexual contacts, estimates of the risk of HIV transmission per sexual act appear to be four to ten times higher in low-income countries than in high-income countries.[57]<\/a><\/sup>\u00a0In low-income countries, the risk of female-to-male transmission is estimated as 0.38% per act, and of male-to-female transmission as 0.30% per act; the equivalent estimates for high-income countries are 0.04% per act for female-to-male transmission, and 0.08% per act for male-to-female transmission.[57]<\/a><\/sup>\u00a0The risk of transmission from anal intercourse is especially high, estimated as 1.4\u20131.7% per act in both heterosexual and homosexual contacts.[57]<\/a><\/sup>[58]<\/a><\/sup>\u00a0While the risk of transmission from\u00a0oral sex<\/a>\u00a0is relatively low, it is still present.[59]<\/a><\/sup>\u00a0The risk from receiving oral sex has been described as \"nearly nil\";[60]<\/a><\/sup>\u00a0however, a few cases have been reported.[61]<\/a><\/sup>\u00a0The per-act risk is estimated at 0\u20130.04% for receptive oral intercourse.[62]<\/a><\/sup>\u00a0In settings involving\u00a0prostitution<\/a>\u00a0in low-income countries, risk of female-to-male transmission has been estimated as 2.4% per act, and of male-to-female transmission as 0.05% per act.[57]<\/a><\/sup>\r\n\r\nRisk of transmission increases in the presence of many\u00a0sexually transmitted infections<\/a>[63]<\/a><\/sup>\u00a0and\u00a0genital ulcers<\/a>.[57]<\/a><\/sup>\u00a0Genital ulcers appear to increase the risk approximately fivefold.[57]<\/a><\/sup>\u00a0Other sexually transmitted infections, such as\u00a0gonorrhea<\/a>,\u00a0chlamydia<\/a>,\u00a0trichomoniasis<\/a>, and\u00a0bacterial vaginosis<\/a>, are associated with somewhat smaller increases in risk of transmission.[62]<\/a><\/sup>\r\n\r\nThe\u00a0viral load<\/a>\u00a0of an infected person is an important risk factor in both sexual and mother-to-child transmission.[64]<\/a><\/sup>\u00a0During the first 2.5\u00a0months of an HIV infection a person's infectiousness is twelve times higher due to the high viral load associated with acute HIV.[62]<\/a><\/sup>\u00a0If the person is in the late stages of infection, rates of transmission are approximately eightfold greater.[57]<\/a><\/sup>\r\n\r\nCommercial sex workers (including\u00a0those in pornography<\/a>) have an increased likelihood of contracting HIV.[65]<\/a><\/sup>[66]<\/a><\/sup>\u00a0Rough sex can be a factor associated with an increased risk of transmission.[67]<\/a><\/sup>\u00a0Sexual assault<\/a>\u00a0is also believed to carry an increased risk of HIV transmission as condoms are rarely worn, physical trauma to the vagina or rectum is likely, and there may be a greater risk of concurrent sexually transmitted infections.[68]<\/a><\/sup>\r\n

Body fluids<\/span><\/h3>\r\n
\r\n
\r\n\r\n[caption id=\"\" align=\"alignleft\" width=\"220\"]\"A<\/a> CDC poster from 1989 highlighting the threat of AIDS associated with drug use[\/caption]\r\n\r\n
\r\n
<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\nThe second-most frequent mode of HIV transmission is via blood and blood products.[13]<\/a><\/sup>\u00a0Blood-borne transmission can be through needle-sharing during intravenous drug use, needle-stick injury, transfusion of contaminated blood or blood product, or medical injections with unsterilized equipment. The risk from sharing a needle during\u00a0drug injection<\/a>\u00a0is between 0.63% and 2.4% per act, with an average of 0.8%.[69]<\/a><\/sup>\u00a0The risk of acquiring HIV from a needle stick from an HIV-infected person is estimated as 0.3% (about 1 in 333) per act and the risk following\u00a0mucous membrane<\/a>\u00a0exposure to infected blood as 0.09% (about 1 in 1000) per act.[49]<\/a><\/sup>\u00a0This risk may, however, be up to 5% if the introduced blood was from a person with a high viral load and the cut was deep.[70]<\/a><\/sup>\u00a0In the United States intravenous drug users made up 12% of all new cases of HIV in 2009,[71]<\/a><\/sup>\u00a0and in some areas more than 80% of people who inject drugs are HIV-positive.[13]<\/a><\/sup>\r\n\r\nHIV is transmitted in about 90% of\u00a0blood transfusions<\/a>\u00a0using infected blood.[41]<\/a><\/sup>\u00a0In developed countries the risk of acquiring HIV from a blood transfusion is extremely low (less than one in half a million) where improved donor selection and\u00a0HIV screening<\/a>\u00a0is performed;[13]<\/a><\/sup>\u00a0for example, in the UK the risk is reported at one in five million[72]<\/a><\/sup>\u00a0and in the United States it was one in 1.5\u00a0million in 2008.[73]<\/a><\/sup>\u00a0In low-income countries, only half of transfusions may be appropriately screened (as of 2008),[74]<\/a><\/sup>\u00a0and it is estimated that up to 15% of HIV infections in these areas come from transfusion of infected blood and blood products, representing between 5% and 10% of global infections.[13]<\/a><\/sup>[75]<\/a><\/sup>\u00a0It is possible to acquire HIV from organ and tissue\u00a0transplantation<\/a>, although this is rare because of\u00a0screening<\/a>.[76]<\/a><\/sup>\r\n\r\nUnsafe medical injections play a role in\u00a0HIV spread in sub-Saharan Africa<\/a>. In 2007, between 12% and 17% of infections in this region were attributed to medical syringe use.[77]<\/a><\/sup>\u00a0The\u00a0World Health Organization<\/a>\u00a0estimates the risk of transmission as a result of a medical injection in Africa at 1.2%.[77]<\/a><\/sup>\u00a0Risks are also associated with invasive procedures, assisted delivery, and dental care in this area of the world.[77]<\/a><\/sup>\r\n\r\nPeople giving or receiving\u00a0tattoos<\/a>,\u00a0piercings<\/a>, and\u00a0scarification<\/a>\u00a0are theoretically at risk of infection but no confirmed cases have been documented.[78]<\/a><\/sup>\u00a0It is not possible for\u00a0mosquitoes<\/a>\u00a0or other insects to transmit HIV.[79]<\/a><\/sup>\r\n

Mother-to-child<\/span><\/h3>\r\nHIV can be transmitted from mother to child during pregnancy, during delivery, or through breast milk, resulting in the baby also contracting HIV.[80]<\/a><\/sup>[13]<\/a><\/sup>\u00a0As of 2008, vertical transmission accounted for about 90% of cases of HIV in children.[81]<\/a><\/sup>\u00a0In the absence of treatment, the risk of transmission before or during birth is around 20%, and in those who also breastfeed 35%.[81]<\/a><\/sup>\u00a0Treatment decreases this risk to less than 5%.[82]<\/a><\/sup>\r\n\r\nAntiretrovirals when taken by either the mother or the baby decrease the risk of transmission in those who do breastfeed.[83]<\/a><\/sup>\u00a0If blood contaminates food during\u00a0pre-chewing<\/a>\u00a0it may pose a risk of transmission.[78]<\/a><\/sup>\u00a0If a woman is untreated, two years of breastfeeding results in an HIV\/AIDS risk in her baby of about 17%.[84]<\/a><\/sup>\u00a0Due to the increased risk of death without breastfeeding in many areas in the developing world, the World Health Organization recommends either exclusive breastfeeding or the provision of safe formula.[84]<\/a><\/sup>\u00a0All women known to be HIV-positive should be taking lifelong antiretroviral therapy.[84]<\/a><\/sup>\r\n

Diagnosis<\/span><\/h2>\r\n
<\/div>\r\n
\r\n
\r\n\r\n[caption id=\"\" align=\"alignright\" width=\"300\"]\"A<\/a> A generalized graph of the relationship between HIV copies (viral load) and CD4+\u00a0T cell counts over the average course of untreated HIV infection. \u00a0\u00a0CD4+\u00a0T Lymphocyte count (cells\/mm\u00b3) \u00a0\u00a0HIV RNA copies per mL of plasma[\/caption]\r\n\r\n<\/div>\r\n<\/div>\r\n\r\n\r\n\r\n\r\n\r\n
Days after exposure needed for the test to be accurate[108]<\/a><\/sup><\/caption>\r\n
Blood test<\/th>\r\nDays<\/th>\r\n<\/tr>\r\n
Antibody test\u00a0(rapid test, ELISA 3rd gen)<\/small><\/td>\r\n23\u201390<\/td>\r\n<\/tr>\r\n
Antibody and p24 antigen test\u00a0(ELISA 4th gen)<\/small><\/td>\r\n18\u201345<\/td>\r\n<\/tr>\r\n
PCR<\/td>\r\n10\u201333<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\nHIV\/AIDS is diagnosed via laboratory testing and then staged based on the presence of\u00a0certain signs or symptoms<\/a>.[25]<\/a><\/sup>\u00a0HIV screening is recommended by the\u00a0United States Preventive Services Task Force<\/a>\u00a0for all people 15\u00a0years to 65\u00a0years of age, including all pregnant women.[109]<\/a><\/sup>\u00a0Additionally, testing is recommended for those at high risk, which includes anyone diagnosed with a sexually transmitted illness.[28]<\/a><\/sup>[109]<\/a><\/sup>\u00a0In many areas of the world, a third of HIV carriers only discover they are infected at an advanced stage of the disease when AIDS or severe immunodeficiency has become apparent.[28]<\/a><\/sup>\r\n

HIV testing<\/span><\/h3>\r\n
\r\n
\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"220\"]\"\"<\/a> HIV Rapid Test being administered[\/caption]\r\n\r\n
\r\n
<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n
\r\n
\r\n\r\n[caption id=\"\" align=\"alignright\" width=\"220\"]\"\"<\/a> Oraquick[\/caption]\r\n\r\n
\r\n
Most people infected with HIV develop specific\u00a0<\/span>antibodies<\/a>\u00a0(i.e.\u00a0<\/span>seroconvert<\/a>) within three to twelve weeks after the initial infection.<\/span>[27]<\/a><\/sup>\u00a0Diagnosis of primary HIV before seroconversion is done by measuring HIV-<\/span>RNA<\/a>\u00a0or\u00a0<\/span>p24 antigen<\/a>.<\/span>[27]<\/a><\/sup>\u00a0Positive results obtained by antibody or\u00a0<\/span>PCR<\/a>\u00a0testing are confirmed either by a different antibody or by PCR.<\/span>[25]<\/a><\/sup><\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\nAntibody tests in children younger than 18\u00a0months are typically inaccurate, due to the continued presence of\u00a0maternal antibodies<\/a>.[110]<\/a><\/sup>\u00a0Thus HIV infection can only be diagnosed by PCR testing for HIV RNA or DNA, or via testing for the p24 antigen.[25]<\/a><\/sup>\u00a0Much of the world lacks access to reliable PCR testing, and people in many places simply wait until either symptoms develop or the child is old enough for accurate antibody testing.[110]<\/a><\/sup>\u00a0In sub-Saharan Africa between 2007 and 2009, between 30% and 70% of the population were aware of their HIV status.[111]<\/a><\/sup>\u00a0In 2009, between 3.6% and 42% of men and women in sub-Saharan countries were tested;[111]<\/a><\/sup>\u00a0this represented a significant increase compared to previous years.[111]<\/a><\/sup>\r\n

Classifications<\/span><\/h3>\r\nTwo main clinical staging systems are used to classify HIV and HIV-related disease for\u00a0surveillance<\/a>\u00a0purposes: the\u00a0WHO disease staging system for HIV infection and disease<\/a>,[25]<\/a><\/sup>\u00a0and the\u00a0CDC classification system for HIV infection<\/a>.[112]<\/a><\/sup>\u00a0The CDC's classification system is more frequently adopted in developed countries. Since the WHO's staging system does not require laboratory tests, it is suited to the resource-restricted conditions encountered in developing countries, where it can also be used to help guide clinical management. Despite their differences, the two systems allow comparison for statistical purposes.[24]<\/a><\/sup>[25]<\/a><\/sup>[112]<\/a><\/sup>\r\n\r\nThe World Health Organization first proposed a definition for AIDS in 1986.[25]<\/a><\/sup>\u00a0Since then, the WHO classification has been updated and expanded several times, with the most recent version being published in 2007.[25]<\/a><\/sup>\u00a0The WHO system uses the following categories:\r\n