Infection with the human immunodeficiency virus (HIV) leads to a progressive destruction of the human immune system. At the point where the immune system is no longer able to defend against pathogens, HIV-positive individuals frequently present with opportunistic infections, and are then considered to have acquired immunodeficiency syndrome (AIDS). The majority of these infectious agents are of little consequence to a person with an intact immune system; however, the unifying theme for opportunistic infections is their increased frequency and severity in those living with HIV. These infections can be divided into several categories, including bacterial, viral, fungal, and protozoan. When an HIV-positive individual has access to and is treated with antiretroviral (ARV) therapy, the incidence of opportunistic infections is reduced but not eliminated. Globally, the majority of those infected with HIV do not have access to ARV therapy, making it important to recognize and treat AIDS-related infections.
The most common bacterial opportunistic infection in those living with HIV is caused by Mycobacterium tuberculosis, the pathogen that causes tuberculosis (TB). TB is transmitted when someone with active disease coughs or sneezes, releasing droplet nuclei of live bacterium into the air. When most people inhale this live bacterium, they develop latent TB infection, and are therefore neither sick nor infectious. Approximately 2 billion individuals worldwide are latently infected with TB. However, the immune destruction related to HIV infection leads to an increased risk of TB reactivation from latency. In individuals who are HIV positive, TB is more difficult to diagnose and progresses faster, leading to increased morbidity and mortality. Active TB infection leads to a severe cough that often progresses to coughing up blood, chest pain, weight loss, chills, fever, and night sweats.
Candida is the most common HIV-related fungal infection, most commonly with Candida albicans, and occurs in over 90 percent of HIV-infected individuals at some point in the course of the disease. Candida is often part of the normal flora of a healthy human mucosa, and overgrowth is kept in check by the immune system. However, in those with HIV, the immune system can no longer control the fungal growth, with infection typically occurring on or around mucous membranes, such as the mouth (thrush), esophagus, and vagina. Oral thrush appears as a white film over the tongue, oral mucosa, and throat. Often the lesions are painful, making eating and drinking difficult with thrush. Vaginal Candida infections are called yeast infections. While any woman can develop a yeast infection, HIV-positive women often get recurrent yeast infections. These women experience frequent vaginal itching and burning, as well as white vaginal discharge.
Viral infections can have severe consequences for those living with HIV. Infection with oncogenic viruses, such as human herpes virus-8, human papilloma virus, and Epstein Barr virus, leads to higher rates of the malignancies Kaposi’s sarcoma, AIDS-related lymphoma, and invasive cervical cancer, respectively. Cytomegalovirus infection (CMV), which is common in the general population, can have severe effects on those with HIV. Most frequently, CMV will cause retinitis, or inflammation of the retina, the layer of cells at the back of the eye. This inflammation can lead to vision changes and rapid progression to blindness.
One of the most common protozoa (single-celled parasite) infections worldwide, encephalitis caused by Toxoplasma gondii, has a significant impact on those living with HIV. Most individuals come into contact with Toxoplasma infection via eating undercooked meat, drinking contaminated water, or contact with cat feces. In someone with a healthy immune system, there is generally no consequence to infection. However, in an HIV-positive individual, a latent infection from within skeletal muscles, heart, or brain will more frequently reactivate. Encephalitis is characterized by headaches, changes in mental status, fever, motor weakness, and speech disturbances. Toxoplasmosis can also cause severe ocular and pulmonary disease in HIV-positive individuals.
As the price of ARV therapy has decreased in recent years, an increasing number of HIV-positive individuals have access to treatment worldwide. However, lack of healthcare infrastructure, a paucity of trained healthcare workers, lack of political will and significant international investment, and stigma surrounding treatment all conspire to prevent universal access to ARV treatment in the developing world. In such a setting, the burden of opportunistic infections remains high. Therefore, prevention and treatment of these diseases may allow for decreased morbidity and mortality.
AIDS; AIDS—Living with AIDS; AIDS-Related Malignancies; National Center for HIV, STD, and TB Prevention (NCHSTP); Tuberculosis.
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