The human immunodeficiency virus (HIV) is a retrovirus that causes AIDS (acquired immune deficiency syndrome). The retrovirus primarily attacks the body's immune system, making the patient extremely vulnerable to opportunistic infections.
Opportunistic infections are conditions that occur in individuals who have a weakened immune system. The organisms (bacteria, fungi or viruses) that cause these infections do not cause illnesses in patients who have healthy immune systems because they are able to fight off the infection.
HIV and AIDS patients are vulnerable to opportunistic infections like Pneumocystis jiroveci pneumonia (formerly called Pneumocystis carinii pneumonia or PCP), mycobacterium avium complex (MAC), toxoplasmosis and tuberculosis. Individuals with a CD4 cell (immune cells that HIV primarily infects and destroys) count lower than 200 cells per microliter of blood have the greatest risk of developing opportunistic infections. Certain infections are considered AIDS-defining illnesses. This means that when HIV-infected patients develop the infection, their condition has progressed to AIDS.
Preventative treatment is taken when HIV-infected patients are at risk of developing these infections, or if they recently had an opportunistic infection.
HIV is transmitted from person to person via bodily fluids, including blood, semen, vaginal discharge and breast milk. It can be spread by sexual contact with an infected person, by sharing needles/syringes with someone who is infected, or, less commonly (and rare in countries like the United States where blood is screened for HIV antibodies), through transfusions with infected blood.
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General: The most common opportunistic infections associated with HIV and AIDS are Pneumocystis jiroveci pneumonia, mycobacterium avium complex (MAC), toxoplasmosis and tuberculosis. Patients at risk of developing these infections typically receive medication to prevent infections
pneumonia: Pneumocystis jiroveci pneumonia (formerly called Pneumocystis carinii or PCP) is the most common opportunistic infection among HIV patients. Originally, researchers thought a one-cell organism called Pneumocystis carinii caused the disease. However, recent research suggests that a fungus called Pneumocystis jiroveci is the cause. The condition is still commonly referred to as Pneumocystis carinii pneumonia (PCP).
According to the National Centers for Disease Control and Prevention (CDC), PCP is considered an AIDS-defining illness. This means that when HIV-infected patients develop PCP, their condition has progressed to AIDS. Individuals with a CD4 cell (helper T-cells that help fight against disease and infection) count lower than 200 cells per microliter of blood have the greatest risk of developing PCP. In addition, people who have CD4 cell counts lower than 300 and have already had another opportunistic infection have an increased risk of developing PCP.
This infection almost always affects the lungs, causing a type of pneumonia. The first signs of PCP are difficulty breathing, fever, and a dry cough. Other common symptoms include chest discomfort, weight loss, chills, tachypnea (rapid breathing), tachycardia (fast heart rate), mild crackles (bubbling or rattling sounds that occur when air moves through fluid-filled airways), cyanosis (bluish discoloration of the skin), nasal flaring and intercostal retractions (visible use of muscles between the ribs, which indicates labored breathing). The patient may also spit up blood, although this is considered a rare symptom.
Historically, mortality ranged from 20-40%, depending on the severity of the disease when it was diagnosed. Today, however, mortality rates range between 10-20%.
Today PCP is almost entirely preventable, and it can be treated effectively with medication. Unfortunately, PCP is still common in patients who are infected with HIV for a long time before they begin antiretroviral therapy (ART). In fact, 30-40% of HIV patients develop PCP if they begin treatment when their CD4 cell counts are around 50.
Mycobacterium avium complex (MAC): Mycobacterium avium complex (MAC), or mycobacterium avium intracellulare (MAI), is a bacterial infection that is caused by either Mycobacterium avium or Mycobacterium intracellulare. These bacteria are commonly found in water, soil, dust and food. In fact, these bacteria are present in almost every human. However, a healthy immune system will prevent the bacteria from causing an infection. Therefore, HIV/AIDS patients are at risk of developing MAC.
According to the CDC, MAC is considered an AIDS-defining illness. It is estimated that up to 50% of individuals with HIV/AIDS develop MAC, especially if their CD4 count is lower than 50 cells per microliter of blood. MAC rarely causes infections in patients who have CD4 cell counts higher than 100 cells per microliter of blood.
MAC infections may be localized (limited to one part of the body) or disseminated (spread throughout the entire body, sometimes called DMAC). MAC infection often occurs in the lungs, intestines, bone marrow, liver and spleen.
Common symptoms of MAC include weight loss, fever, chills, night sweats, swollen glands, abdominal pain, diarrhea, inflammation and a general feeling of overall weakness. MAC usually affects the intestines and inner organs first.
The most common complication of DMAC is anemia (low levels of red blood cells), which may require a blood transfusion. If the infection involves many organs, it may lead to respiratory failure and death. Patients who have localized infections have a low mortality rate.
Toxoplasmosis: Toxoplasmosis (toxo) is a parasitic infection that is caused by a single-celled parasite called Toxoplasma gondii.
Toxoplasma gondii is one of the most common parasites, found all over the world. Individuals may be exposed to the parasite in soil, cat feces or in raw or undercooked meat (especially lamb, pork or venison). There have also been rare reports of toxoplasmosis infection as a result of organ transplantation or blood transfusion.
It is estimated that more than 60 million Americans carry the parasite. However, 80-90% of infected patients are carriers (experience no symptoms) because the body's immune system prevents the parasite from causing illness. Toxoplasmosis is considered an AIDS-defining illness, according to the CDC.
HIV patients often experience symptoms such as headache, confusion, poor coordination, seizures, ocular toxoplasmosis (severe inflammation of the retina), as well as lung problems that are similar to tuberculosis or pneumocystis pneumonia (lung infections).
Tuberculosis: Tuberculosis (TB) is a bacterial infection of the lungs, which is caused by the microorganism Mycobacterium tuberculosis. Symptoms may include cough, shortness of breath, pleurisy (pain with breathing or coughing), fever, weight loss, night sweats, chills and loss of appetite. The disease can cause serious respiratory problems, which can be life threatening, especially if left untreated.
Tuberculosis is highly contagious. The disease is transmitted through airborne droplets when a person with the infection coughs, talks or sneezes.
About 10 to 15 million Americans have latent TB infection, which means they are not sick, but they carry the bacterium that causes the disease. Only 10% of individuals with latent TB ever develop the infection.
While tuberculosis is not considered an AIDS-defining illness, HIV patients have an increased risk of developing TB because they have weakened immune systems. The risk of developing active TB increases 7-10% in HIV patients who have latent TB. HIV patients are more likely to experience symptoms in areas of the body other than the lungs. This is called extrapulmonary TB. The disease may affect the bones, joints, nervous system or urinary tract. Also, TB appears to make HIV infection worse. Researchers have found that HIV replicates faster when tuberculosis is also present.