AIDS occurs in patients who suffer from a severe and long unrecognized human immunodeficiency virus (HIV) infection (caused by either HIV-1 or HIV-2 virus) [1] [2] [3]. AIDS is almost never encountered in patients with an acute HIV infection, but rather develops after the period of latency and progressive decrease in CD4+T-cell function [4] [5]. One of the most important risk factors is the lack of treatment, mostly because of a missed (or unknown) diagnosis. The progressive nature of HIV infection symptoms and infections have been grouped into two diagnostic criteria devised by the Center for Disease Control (CDC) and the World Health Organization (WHO). As per CDC criteria, three distinct categories exist - A, B, and C, with A describing features of acute or asymptomatic HIV infection [2] [6]. On the other hand, categories B and C (similarly to clinical stages 2,3 and 4 of WHO criteria) include the appearance of AIDS-related conditions. Constitutional symptoms such as fever, fatigue, or diarrhea lasting for at least one month, peripheral neuropathy and numerous infections - Listeriosis, Bacillary angiomatosis, recurrent herpes zoster involving > 1 dermatome and pelvic inflammatory disease (PID) are initial signs of AIDS [1] [2] [3] [6] [7]. Candidiasis, however, is the most important group B feature of patients with suspected HIV or AIDS and can present in the oropharynx or the genitalia. Additional disorders that belong to the B category are immune thrombocytopenic purpura (ITP), cervical dysplasia (or cervical carcinoma in situ) and oral hairy leukoplakia. When patients present with profound weight loss and poor general condition due to "wasting syndrome" caused by HIV, they are adequately classified into category C and clinical stage 4, respectively, and signs of severe AIDS include [1] [2] [3] [6] [7]:

• Infections - Candidiasis (esophageal, pulmonary, or tracheal), pneumocystis jirovecii pneumonia (PCP), coccidiomycosis (either extrapulmonary or disseminated), extrapulmonary cryptococcosis, cytomegalovirus (CMV) infection of sites other than the spleen, lymph nodes or liver (such as pneumonia or retinitis), herpes simplex virus (HSV) infection of the respiratory system or the esophagus, histoplasmosis, intestinal isosporiasis, mycobacterial infections (both by tuberculous and by non-tuberculous mycobacteria, most notably M. avium), cerebral toxoplasmosis, recurrent pneumonias and severe infections by Salmonella spp.
• Malignancies - Lymphomas, Kaposi's sarcoma, and invasive cervical cancer.
• Other conditions - Progressive multifocal leukoencephalopathy (PML), HIV-related encephalopathy that can present with various neurological symptoms, including dementia (also known as the AIDS dementia complex).

Because many disorders are a part of the clinical presentation of AIDS, physicians must maintain a high index of suspicion when any of the mentioned illnesses or infections appear together with a poor general condition. For this reason, a comprehensive workup is necessary to rule out HIV infection and AIDS as a possible cause [2]. Firstly, a detailed patient history must include assessment of potential risk factors such as unprotected sexual intercourse, particularly male homosexual (as the vast majority of patients in the developed world are males belonging to the men having sex with men - MSM population), contact with blood products (through intravenous drug use) or a positive family history in the setting of vertical transmission [2] [6] [7]. Moreover, the appearance of any of the infections (or their respective signs and symptoms) in recent months should be noted, and a detailed and complete physical examination may confirm cutaneous, pulmonary, or general manifestations of AIDS and warrant a laboratory investigation to diagnose the clinical entity. A neurological exam (including the mini-mental status examination) must be carried out in all patients suspected to have severe HIV infection, in order to assess the extent of neurological involvement and detect AIDS-related dementia. In addition to a complete blood count (CBC), which will show lymphopenia in virtually all patients, an extensive biochemical panel is necessary to evaluate organ status - lipid profile, liver and kidney function, and a full electrolyte panel [2] [3] [7]. If the diagnosis of HIV is not already known, testing for HIV antibodies is the first step in confirming this infection, followed by a CD4+T-cell count and isolation of viral RNA through polymerase chain reaction (PCR) analysis. Classification of patients harboring an HIV infection, supplementary to clinical criteria, is based on the CD4+T-cell count as well, and a number of < 200/µL is diagnostic for AIDS [2]. Additional recommended procedures include syphilis testing with the Venereal disease research laboratory test (VDRL) and rapid plasma reagin (RPR) tests, detection of anti-toxoplasma antibodies, purified protein derivative (PPD) test for tuberculosis, and determine possible coinfection by hepatitis viruses (A, B, or C) [3] [6] [7].

While there is no cure for HIV/AIDS, it can be managed with antiretroviral therapy (ART). ART involves taking a combination of HIV medicines every day. ART helps control the virus, allowing individuals to live longer, healthier lives and reducing the risk of transmission. Treatment is most effective when started early, before the immune system is severely damaged. Regular monitoring and adherence to the treatment regimen are crucial for its success.

With proper medical care, HIV can be controlled. Most people with HIV do not develop AIDS if they start ART soon after becoming infected. However, without treatment, people with AIDS typically survive about three years. Once someone has a dangerous opportunistic illness, life expectancy without treatment falls to about one year. ART can significantly improve life expectancy and quality of life.

AIDS is caused by the human immunodeficiency virus (HIV). HIV is transmitted through contact with infected blood, semen, vaginal fluids, or breast milk. The most common ways HIV is spread are through unprotected sexual contact, sharing needles, and from mother to child during childbirth or breastfeeding. It is important to note that HIV cannot be spread through casual contact, such as hugging or sharing food.

HIV/AIDS is a global pandemic, affecting millions of people worldwide. Sub-Saharan Africa is the most affected region, with a significant number of new infections and deaths. In recent years, the number of new infections has decreased due to increased awareness, prevention efforts, and access to treatment. However, certain populations, such as men who have sex with men, people who inject drugs, and sex workers, remain at higher risk.

HIV primarily targets the immune system, specifically the CD4 T cells. The virus enters these cells, replicates, and eventually destroys them. As the number of CD4 cells decreases, the immune system becomes weaker, making the body more susceptible to infections and certain cancers. The progression from HIV to AIDS occurs when the immune system is severely compromised, and the body can no longer defend itself against opportunistic infections.

Preventing HIV infection is key to stopping the spread of AIDS. Strategies include practicing safe sex by using condoms, getting tested and knowing your partner's HIV status, limiting the number of sexual partners, and never sharing needles. Pre-exposure prophylaxis (PrEP) is a medication that can be taken by people at high risk of HIV to prevent infection. Additionally, pregnant women with HIV should receive treatment to reduce the risk of mother-to-child transmission.

Acquired Immunodeficiency Syndrome (AIDS) is a severe condition caused by the human immunodeficiency virus (HIV), which attacks and weakens the immune system. While there is no cure, antiretroviral therapy (ART) can effectively manage the disease, allowing individuals to live longer, healthier lives. Prevention strategies are crucial in reducing the spread of HIV and ultimately preventing AIDS.

If you or someone you know is living with HIV/AIDS, it is important to seek medical care and adhere to prescribed treatments. Regular check-ups and monitoring are essential to managing the condition. Educating yourself about HIV/AIDS, practicing safe behaviors, and supporting those affected can help reduce stigma and improve outcomes for everyone involved.

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3. Porter RS, Kaplan JL. Merck Manual of Diagnosis and Therapy. 19th Edition. Merck Sharp & Dohme Corp. Whitehouse Station, N.J; 2011.
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5. GBD 2015 HIV Collaborators. Estimates of global, regional, and national incidence, prevalence, and mortality of HIV, 1980–2015: the Global Burden of Disease Study 2015. Lancet HIV. 2016 Aug; 3(8):e361–e387.
6. Centers for Disease Control and Prevention (CDC). Revised surveillance case definition for HIV infection--United States, 2014. MMWR Recomm Rep. 2014;63(RR-03):1-10.
7. Longo DL, Fauci AS, Kasper DL, Hauser SL, Jameson J, Loscalzo J. eds. Harrison's Principles of Internal Medicine, 18e. New York, NY: McGraw-Hill; 2012.