Acquired immunodeficiency syndrome or SIDA (síndrome da imunodeficiência adquirida, syndrome d’immunodéficience acquise, etc) exploded onto the medical scene with the 1981 report in the MMWR* of five cases of Pneumocystis carinii (later renamed Pneumocystis jirovecii) pneumonia in previously healthy homosexual men who lived in Los Angeles. This triggered a wider investigation with more cases identified in NYC, San Francisco and elsewhere. The editorial in the same issue of the MMWR suggested a cellular immune dysfunction related to a common exposure, specifically sexual contact. 

*Morbidity and Mortality Weekly Report (5 June 1981), produced by the CDC (Centers for Disease Control and Prevention in Atlanta)

AIDS HIV1 image from New Medical Terms

schematic of HIV-1, key proteins and antigenic sites

The CDC ran with it and within 18 months had identified the major risk factors (sexual contact, intravenous drug use, occupational exposure to blood, transfusions, and therapeutic blood products) and developed a working case definition before the actual cause of the disease was identified. In 1983, the virus causing AIDS was identified, and initially named HTLV-III/LAV (human T-cell lymphotropic virus-type III/lymphadenopathy-associated virus). The name was later changed to HIV (human immunodeficiency virus), of which there are two types, HIV-1 and HIV-2. HIV-1 is far more prevalent, constitutes 95% of cases of HIV infection, and causes more serious clinical disease. HIV-2 constitutes about 5% of HIV-infections, most of the cases are in Western Africa and the clinical course of disease is less aggressive than HIV-1. 

The first stage of disease is acute HIV infection, which is often accompanied by flu-like or mononucleosis-like symptoms, with pharyngitis, fever, tender lymphadenopathy, headache, oral and genital ulcers and in up to half of cases, a maculopapular rash. Because early infection is often misdiagnosed or passed off as a banal flu, testing for HIV status should be part of the workup for any person with unexplained fever who has known AIDS risk factors. Some patients develop opportunistic infections (OIs) during the acute HIV infection phase of disease, but early OIs are not the norm. 

Acute infection with HIV is typically followed by a period known as clinical latency, asymptomatic HIV infection, or chronic HIV infection which, without antiretroviral therapy, can last from 3 to 20 years. As the latency stage draws to a close, patients develop fever, weight loss, GI complaints, and myalgia; over half of patients develop generalized painless lymphadenopathy. As CD4+ T (helper) cells fall below 200/µl. 

AIDS:HIV Prevalence image from New Medical Terms

Global prevalence of AIDS and HIV-1

The drop in CD4+ T cells usually marks the beginning of the götterdämmerung known as AIDS, which includes a plethora of conditions classically associated with advanced HIV infection, including P jirovecii pneumonia, HIV-wasting syndrome, and esophageal candidiasis. In addition to an array of OIs–e.g., tuberculosis, CMV, cryptosporidiosis, and Mycobacterium avium complex, these patients’ compromised immune systems put them at risk of virally-induced malignancies including Kaposi sarcoma (due to HHV-8 infection), Burkitt lymphoma (EBV infection), cervical cancer (HPV), as well as primary CNS lymphoma. As AIDs progresses, patients may develop treatment-refractory diarrhea, fever, night sweats, and unintended weight loss. 

The good news, such as it is, is that HIV/AIDS is no longer considered an acutely fatal disorder, but rather a chronic disease that can be managed with the currently available therapeutic cocktails. But without treatment, HIV infection and AIDs are still lethal. The norm from HIV infection to death from AIDS without treatment is 10 years; once AIDS develops, without treatment, the average person will be dead within a year. The later treatment begins, the worse the prognosis. Half of infants born with HIV will die by age 2 without treatment. 

HIV/AIDS is a global pandemic. In 2016, there were 36.7 million  HIV-infected people in the world, of which 1.8 million were new infections, compared to 3.1 million new infections in 2001. In 2016, 1 million people died from AIDS, down from a 2005 peak of 1.9 million deaths. South Africa has the highest concentration of HIV infections with 15%-50% of young adults infected (indicated in red on the accompanying map). The life expectancy in the worst-hit countries (Botswana) has dropped from 65 years to 35 years, a drop entirely attributed to HIV/AIDS. The disease has killed 30 million people since it was first recognized.