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HIV / AIDS Opportunistic Infections and Symptoms

Medically reviewed by Leigh Ann Anderson, PharmD. Last updated on Sep 22, 2019.

Introduction | AIDS Defined | HIV Symptoms | List of AIDS-Defining Illnesses | List of Opportunistic Infections (OIs) | Table: HIV Symptoms in Children | Details of OIs | Prevention of OIs

What is HIV infection?

Once the Human Immunodeficiency Virus (HIV) has entered the body, the immune system comes under attack. The HIV virus multiplies and slowly begins to destroy the CD4 lymphocytes (T-cells), which are the white blood cells that are important to help fight off infections. Even if the person with HIV feels well with no symptoms, HIV is still invading the CD4 cells. The immune system weakens progressively over time and becomes susceptible to bacterial, viral, fungal and parasitic infections, also called "opportunistic" infections.

As more serious symptoms and complications appear, the HIV infection may then meet the official definition of AIDS:

  • a positive HIV-antibody ELISA followed by a confirmatory Western Blot test or other HIV virologic test (HIV nucleic acid test, HIV p24 antigen test, HIV viral culture)
  • and either:
    • the onset of an "AIDS-defining" illness, such as an infection or cancer
    • or a CD4 T-cell count of 200 cells/mm3 (a normal count ranges from 600 to 1000 cells/mm3) or a CD4 T-cell percentage of total lymphocytes of <14.

Antiretroviral therapy (ART) is the backbone of HIV treatment today and is necessary to help prevent possible life-threatening opportunistic infections and AIDS-related illnesses and cancers. 

Learn More: HIV and AIDS Medications and Drug Classes

How is AIDS defined?

If a person infected with HIV has:

  • CD4 count of less than 200 cells/mm3
  • a CD4 T-lymphocyte percentage of total lymphocytes of less than 14%
  • and/or an AIDS-defining illness

they are said to have AIDS. In order for a patient who is infected with HIV to have AIDS, the immune system must be severely damaged. The severity of the immune system damage is measured by a CD4 lymphocyte (white blood cell) count. Patients are at greatest risk of developing opportunistic infections when the CD4 count gets below 200 cells/mm3.

The difference between AIDS-defining illness and opportunistic infection

AIDS-defining illnesses are directly linked with the damage of the immune system as a result of HIV infection. AIDS-defining illnesses tend to occur in the later stages of the disease in patients who have not received antiretroviral treatment (ART) for HIV infection and who have a very low CD4 count. HIV may be initially diagnosed when these patients present to the doctor to the first time with one of these infections or cancers. When a person gets one of these illnesses, he or she is diagnosed with the advanced stage of HIV infection known as AIDS.

Opportunistic infections occur more often or more frequently when the immune system is weak, as with HIV/AIDS. People with weakened immune systems include people living with HIV/AIDS, but might also include people with cancers of the immune system like leukemia or multiple myeloma, or immune-complex diseases like viral hepatitis.

Common HIV symptoms

It is common to develop a brief flu-like illness 2 to 6 weeks after being infected with HIV. The symptoms may include:

  • fever
  • headache
  • sore throat
  • swollen lymph glands
  • rash

These symptoms are similar to many other diseases and may not be recognized as HIV infection initially.

Initial infection with the HIV virus may produce little to no symptoms. The length of time between initial HIV infection and the development of AIDS varies greatly and some people may remain without symptoms for years. Many people remain symptom free for 10 years or longer but during this time the virus continues to multiply and destroy their immune cells for people who are not on antiretroviral therapy (ART). However, even though a person does not have symptoms, they can still transmit the virus to others. 

The Centers for Disease Control (CDC) states the following may be warning signs of HIV infection but cautions that any of these symptoms can be related to other illnesses. Only an HIV blood test can be used for an accurate diagnosis of HIV:

  • rapid weight loss
  • dry cough and shortness of breath
  • recurring fever or profuse night sweats
  • profound and unexplained fatigue
  • swollen lymph glands in the armpits, groin, or neck
  • diarrhea that lasts for more than a week
  • white spots or unusual blemishes on the tongue, in the mouth, or in the throat
  • pneumonia
  • red, brown, pink, or purplish blotches on or under the skin, or inside the mouth, nose, or eyelids
  • memory loss, depression, or other neurological disorders.

During the last phase of HIV, which can occur up to 10 or 11 years after the initial infection, the immune system will have been severely damaged, making the body highly susceptible to a large number of bacterial, viral, fungal and parasitic (also called opportunistic) infections.

The symptoms of some of these infections may include:

  • shaking chills or fever higher than 100 F for several weeks
  • soaking night sweats
  • dry cough and shortness of breath
  • chronic diarrhea
  • persistent white spots or unusual lesions on the tongue or in the mouth
  • persistent headaches
  • blurred and distorted vision
  • weight loss
  • persistent, unexplained fatigue
  • swelling of lymph nodes for more than three months

People with HIV infection are also at greater risk of developing certain cancers, especially Kaposi's sarcoma, cervical cancer and lymphoma.

List of AIDS-defining illnesses in HIV and AIDS

The following list are conditions that are "AIDS-defining", as published by the CDC. The CDC now refers to this list as "AIDS-defining conditions". Many other illnesses and corresponding symptoms may develop in addition to those listed here:

  • Bacterial infections, multiple or recurrent
  • Candidiasis of bronchi, trachea, or lungs
  • Candidiasis of esophagus
  • Cervical cancer, invasive
  • Coccidioidomycosis, disseminated or extrapulmonary
  • Cryptococcosis, extrapulmonary
  • Cryptosporidiosis, chronic intestinal (>1 month's duration)
  • Cytomegalovirus disease (other than liver, spleen, or nodes), onset at age >1 month
  • Cytomegalovirus retinitis (with loss of vision)
  • Encephalopathy, HIV related
  • Herpes simplex: chronic ulcers (>1 month's duration) or bronchitis, pneumonitis, or esophagitis (onset at age >1 month)
  • Histoplasmosis, disseminated or extrapulmonary
  • Isosporiasis, chronic intestinal (>1 month's duration)
  • Kaposi sarcoma
  • Lymphoid interstitial pneumonia or pulmonary lymphoid hyperplasia complex
  • Lymphoma, Burkitt (or equivalent term)
  • Lymphoma, immunoblastic (or equivalent term)
  • Lymphoma, primary, of brain
  • Mycobacterium avium complex or Mycobacterium kansasii, disseminated or extrapulmonary
  • Mycobacterium tuberculosis of any site, pulmonary, disseminated, or extrapulmonary
  • Mycobacterium, other species or unidentified species, disseminated or extrapulmonary
  • Pneumocystis jirovecii pneumonia
  • Pneumonia, recurrent
  • Progressive multifocal leukoencephalopathy
  • Salmonella septicemia, recurrent
  • Toxoplasmosis of brain, onset at age >1 month
  • Wasting syndrome attributed to HIV

List of common opportunistic infections in HIV and AIDS

The symptoms of AIDS are primarily the result of infections known as opportunistic infections (OIs) that do not normally develop in individuals with healthy immune systems. OIs are less common today because of advances in HIV treatments and the ability to help keep a person's immune system stronger.

  • Candidiasis (fungal infection) of the bronchi, trachea, esophagus, or lungs 
  • Coccidioidomycosis - a type of fungal pneumonia due to Coccidioides immitis 
  • Cryptococcosis - fungal infection due to Cryptococcus neoformans 
  • Cryptosporidiosis - diarrheal disease is caused by the protozoan parasite Cryptosporidium
  • Cytomegalovirus (CMV) diseases - may affect eye (can lead to blindness with CMV retinitis), lungs, stomach 
  • Encephalopathy, HIV-related - brain disease 
  • Herpes simplex virus infection (HSV): chronic ulcer(s) (greater than one month’s duration); or bronchitis, pneumonitis, or esophagitis 
  • Histoplasmosis - fungal lung infection due to Histoplasma capsulatum 
  • Isosporiasis, chronic intestinal (greater than one month’s duration) 
  • Invasive cervical cancer 
  • Kaposi's sarcoma (KS)
  • Lymphoma, multiple forms 
  • Mycobacterium avium complex (MAC), or Mycobacterium kansasii, disseminated or extrapulmonary, or other Mycobacterium infections 
  • Pneumocystis jiroveci pneumonia (PCP) - fungal lung infection (previously called Pneumocystis carinii
  • Pneumonia, recurrent 
  • Progressive multifocal leukoencephalopathy 
  • Salmonella septicemia, recurrent 
  • Toxoplasmosis of the brain - caused by the parasite Toxoplasma gondii 
  • Tuberculosis (TB) - due to Mycobacterium tuberculosis
  • Wasting syndrome due to HIV

are some of the most common HIV-related opportunistic infections seen in clinical practice, as noted by the CDC.

HIV symptoms in children

As reported in 2019, about 12,000 children, teens and young adults in the U.S. have had HIV since they were born. Common symptoms due to HIV in a child can vary depending upon age (infant, child, or adolescent). Most babies with HIV appear healthy at birth, but if the condition is left undiagnosed and untreated, signs or symptoms may appear within 2 to 3 months. 

HIV Symptoms in Children Description
Failure to thrive, weight loss Delayed bone growth and weight gain, common in infants with HIV; weight loss may occur in older children.
Swollen abdomen (stomach) Due to swelling of the liver and spleen. 
Swollen lymph nodes or parotid glands, fever, headache, tiredness May present as a flu-like illness within a month or two after exposure to the HIV virus.
Diarrhea May be ongoing or recurrent.
Pneumonia Often due to Pneumocystis jiroveci pneumonia.
Oral thrush or other systemic yeast infections Oral thrush is a fungal infection in the mouth that may be painful; can last for 2 months or more.
Constant or recurring ear infections Mild symptoms usually seen in children > 1 year old.
Constant or recurring sinus infections Mild symptoms usually seen in children > 1 year old.
Dermatitis Skin rashes or flaky skin
Hepatitis Liver inflammation usually in children > 1 year old
Complications due to chicken pox  Typically occurs in children > 1 year old

Due to advances in treatment, children who are diagnosed and receive appropriate medical care and medications early in life can have similar positive outcomes as seen in adults. As with adults, antiretroviral therapy (ART) is a key component of managing symptoms, opportunistic infections, and reducing the risk of transmission.

Learn More: How Can HIV and AIDS Be Prevented?

Details of Opportunistic infections

Tuberculosis (TB)

Tuberculosis is a common opportunistic infection that predominantly affects the lungs. However, it can spread through the blood and affect the larynx, lymph nodes, brain, kidneys, or bones in people with HIV. TB is caused by by the Mycobacterium tuberculosis bacterium and is common in people with HIV.

TB in the lungs causes a long-term cough that may produce blood and may also cause fever, weight loss, tiredness, and night sweats. The disease can strike people with HIV no matter what the level of their CD4 count, which means that TB can often occur years before other problems associated with HIV develop. 

Everyone who is HIV-positive should have a simple skin test for TB. If the test is positive, a chest X-ray and other tests will determine if the infection is active. If the TB is not active, preventative treatments are available.

Tuberculosis is more worrisome than many other opportunistic infections because of the ease with which it is spread (by coughing, sneezing, or speaking) from one person to another. Multi-drug Resistant-Tuberculosis (MDR-TB) is resistant to traditional treatments and is of particular concern to people with HIV and AIDS.

Anyone with HIV can get tuberculosis but it is more likely to occur in those with CD4 counts of less than 200 cells/mm3.

Herpes simplex virus (HSV)

Herpes Simplex virus (HSV), which usually causes genital herpes, may be transmitted during unprotected sex or from an infected mother during childbirth. Usually the symptoms and virus are inactive (latent) in people with health immune systems, but in HIV, stressful events, or trauma, the symptoms can appear. Initial symptoms include pain or irritated skin in the mouth, genital area, anus, and later sores that may erupt and ooze and bleed. Although these sores eventually heal, the virus periodically reappears, causing the same symptoms.

The symptoms of HSV are more severe in people with HIV and the sores may take longer to heal (over one month in duration). The herpes virus isn't usually life-threatening in adults, but it may cause brain damage, blindness or death in infants infected during delivery. In more advanced HIV, HSV can cause infection of the lungs such as pneumonia (infection of the lungs) or esophagitis (infection of the esophagus).

Anyone with HIV can get HSV, regardless of their CD4 count.

Candidiasis in HIV

Candidiasis (thrush) is a yeast infection of the mouth or genitals and is a very common HIV-related infection. The symptoms include inflammation and a thick white coating on the mucous membranes of the mouth, tongue, vagina or esophagus (Candida esophagitis). Children may have especially severe symptoms in the mouth or esophagus, which can make eating painful and difficult. Uncomplicated, severe or recurrent vulvovaginal candidiasis (in the genital area) may also occur.

Candidiasis of the bronchi, trachea, lungs or esophagus is considered opportunistic or "AIDS-defining", but oral or vulvovaginal candidiasis are not considered "AIDS-defining" in an HIV infected individual.

Anyone with HIV can get candidiasis but it is more dangerous in those with CD4 counts of less than 200 cells/mm3.

Read More: Candidiasis Health Guide

Lymphomas in HIV

Non-Hodgkin's Lymphoma (NHL) is a cancer of the lymph glands originating in the lymphocytes, a type of white blood cell involved in fighting infection. NHL usually starts in the lymph nodes but can also start in the liver, lungs or gastrointestinal tract. The most common symptom of NHL is swollen (usually painless) lymph nodes in the neck, armpit or groin. Other symptoms include fever, night sweats, fatigue, itchy skin and weight loss, aches, and sometimes coughing, difficulty breathing and chest pain.

Non-hodgkin lymphoma has become more common in the past few decades. This may be related to the rise in the number of people who have a suppressed immune system, such as people infected with HIV and those who have had an organ transplant and need to take drugs that alter the immune system.

Other AIDS-defining lymphomas include Burkitt lymphoma and brain lymphoma.

Anyone with HIV can get non-hodgkin's lymphoma but it is more likely in those with CD4 counts of less than 200 cells/mm3 .

Salmonella in HIV

Salmonellosis (food poisoning) is an infection caused by the salmonella bacterium, which is contracted from contaminated food or water. Symptoms include severe diarrhea, fever, chills, abdominal (stomach) pain and sometimes vomiting. The risk of contracting salmonellosis can be reduced by hand washing and by thoroughly cooking your meat and eggs.

Salmonella septicemia (a severe infection in the blood) usually is treated with antibiotics. Drug therapy may be required for life to prevent relapses. HIV patients should avoid having reptiles as pets due to the possible transmission of salmonella.

Anyone with HIV can get salmonellosis, regardless of their CD4 count.


Human Papillomavirus (HPV) is one of the most common causes of sexually transmitted disease. Some types of this virus cause common warts while others cause warts on the genitals. HPV infection is especially serious because it puts women at risk of invasive cervical cancer; the risk is further increased in women with HIV.

Anyone with HIV can get HPV but women with CD4 counts of less than 50 cells/mm3 are more likely to develop HPV-related growths in the cervix.

Cryptosporidiosis in HIV

Cryptosporidiosis is an infection contracted by ingesting contaminated food or water. The Cryptosporidium protozoan parasite grows in the intestines and bile ducts and can cause severe, watery diarrhea. Symptoms are chronic (long-lasting) in patients with AIDS, typically lasting longer than one month.

Anyone with HIV can get cryptosporidiosis; however, it is particularly dangerous for those with a CD4 count of 50 cells/mm3 or less.

Pneumocystis jiroveci pneumonia (PCP) in HIV

Pneumocystis jiroveci pneumonia, previously known as Pneumocystis carinii pneumonia (PCP) is one of the most common opportunistic infection that occurs with AIDS in the U.S. The fungus that causes the PCP infection is spread through breathing or coughing.

Symptoms include persistent dry cough, fever, trouble breathing (lips and nail-beds may become blue), fatigue, and weight loss. Medications such as sulfamethoxazole/trimethoprim (Bactrim) is frequently used to treat and prevent PCP.

PCP is particularly dangerous for those with a CD4 count of less than 200 cells/mm3 .

Recurrent pneumonia in HIV

Studies have shown that persons with HIV-related immunosuppression are at an increased risk of  pneumonia, an infection of the lungs that can be caused by bacteria, viruses, or fungi. Symptoms include cough, often with mucous production, fever, chills, and difficult breathing. Streptococcus pneumoniae, also called Pneumococcus, can be prevented with a vaccine that all HIV-infected people should receive.

Recurrent episodes of pneumonia (two or more episodes within a 1-year period) are more strongly associated with immunosuppression than are single episodes.

Patients with CD4 counts less 200 cells/mm3 may be at higher risk of recurrent episodes of pneumonia.

Kaposi's sarcoma (KS) in HIV

Kaposi's sarcoma (KS) is the most common AIDS-related cancer and is caused by a herpes virus. It is a cancer of the blood capillary vessel walls and leads to abnormal growth of these vessels. Common symptoms are pink, red or purple lesions on the skin and in the mouth. The first spots, sores or bumps usually appear on the face, nose, mouth, arms, upper body or legs. The lesions vary from pinhead size to the size of a large coin and may be painless. Sometimes the skin lesions are painful and can cause itching and sores in the mouth or throat may cause eating or swallowing problems.

Kaposi's sarcoma can also affect the internal organs, including the digestive tract, lymph nodes and lungs and be life-threatening.

Anyone with HIV can get Kaposi's Sarcoma, but it is more likely in those with CD4 counts of less than 200 cells/mm3.

Coccidioidomycosis in HIV

Coccidioidomycosis is a fungal infection that progresses to chronic localized disease of the lungs or other organs such as bone, skin, and meninges. It is caused by the fungus Coccidiodes immitis. Lung involvement is most common in patients with AIDS. It is often called desert fever, San Joaquin Valley fever, or valley fever. It is common in the Southwest part of the U.S. as well as Central and South America.

Learn More: Compare drugs associated with Coccidioidomycosis

Cryptococcal meningitis in HIV

Cryptococcal meningitis, caused by a fungus, is the most common central nervous system infection associated with HIV. Meningitis is an inflammation of the membranes and fluid surrounding the brain and spinal cord (meninges). Symptoms include headache, high fever, stiff neck, and sensitivity to light. Meningitis is a serious disease that can cause severe complications and even prove fatal in a short amount of time.

Cryptococcal Meningitis is particularly dangerous in those with a CD4 count of 50 cells/mm3 or less.

Toxoplasmosis in HIV

Toxoplasmosis, caused by a parasite spread primarily by cats, rodents, and birds, is the most common cause of brain lesions in people with advanced HIV disease. It is caused by the parasite Toxoplasma gondii. Humans can become infected by eating food or inhaling dust contaminated with the parasite. Gloves should always be worn when changing the cat litter box, and afterwards, hands should be thoroughly washed with soap and warm water.

Toxoplasmosis often leads to encephalitis, an infection of the brain. Symptoms may include disorientation, seizures, fatigue, headaches and difficulty walking or speaking. Infection can also occur in the lungs, eye, heart, pancreas, liver, colon, and testes.

Toxoplasmosis is particularly dangerous in those with a CD4 count of 100 cells/mm3 or less.

Progressive multifocal leukoencephalopathy (PML) in HIV

Progressive Multifocal Leukoencephalopathy (PML) is an extremely serious viral disease of the brain. PML causes a quick decline in cognitive (thinking) and motor functions (movement) of the body.

Symptoms vary and may include speech problems, weakness on one side of the body, loss of vision in one eye, or numbness in one arm or leg. PML is a late-stage disease that occurs only when the immune system is severely damaged.

Mycobacterium avium complex (MAC) in HIV

Mycobacterium avium complex (MAC) is a common AIDS infection caused by a bacterium related to tuberculosis, as well as Mycobacterium intracellulare or Mycobacterium kansasii. The mycobacteria are present in the soil and rarely cause issues for those with a healthy immune system.

Normally, the bacterium causes an infection of the respiratory tract but, in advanced HIV or AIDS, an infection can affect almost any internal organ, including the bone marrow, liver or spleen. MAC causes nonspecific symptoms such as cough, fever, night sweats, weight loss, fatigue, stomach pain, and diarrhea.

MAC is particularly dangerous in those with a CD4 count of 50 cells/mm3 or less.

Cytomegalovirus (CMV) in HIV

Cytomegalovirus infection (CMV) is a viral infection that can affect almost any organ system. A healthy immune system inactivates the virus and it therefore remains dormant in the body. If the immune system weakens, as in untreated HIV, the virus resurfaces. Pneumonia, intestinal tract infections, brain infections, and eye retina infections (which may lead to blindness) can occur. 

Symptoms include fatigue, fever, enlarged lymph nodes and pain in the muscles or throat. CMV can cause damage to the eyes (retinitis), digestive tract (diarrhea), lungs (pneumonia), liver (hepatitis), or other organs. CMV retinitis is a medical emergency as it can cause blindness.

CMV is particularly dangerous in those with a CD4 count of 50 cells/mm3 or less.

Learn More: Drug Treatment of AIDS Complications

Other Conditions and Complications

  • AIDS Related Wasting Syndrome - Extreme weight loss and anorexia caused by HIV.
  • AIDS Dementia - Worsening and slowing of mental function caused by HIV.
  • Encephalopathy, HIV-related - Damage to the brain due to HIV disease. It may result in a form of dementia in advanced HIV disease.
  • Histoplasmosisa fungal infection caused by Histoplasma capsulatum, which primarily affects the lungs or other organs.
  • Isosporiasis - caused by infection with a species of Isospora; can lead to intractable diarrhea.

Can you prevent opportunistic infections?

Opportunistic infections (OIs) are less common in the U.S. now than they were in the past due to advances in detection times and treatment options. If you have been diagnosed with HIV, the best way to prevent complications is to visit your doctor on a regular basis, take your medications as prescribed, and learn to help to protect your immune system.

  • Continue to use safe sex practices to help avoid getting other sexually transmitted diseases.
  • Do not share needles or other equipment that has been used by others. This can increase your risk for contracting hepatitis.
  • Get vaccinated - speak to your doctor about which vaccines you should get, and if you need them only once or on a regular basis.
  • Avoid foods that might be contaminated, such as unpasteurized or raw milk and cheese, unpasteurized fruits juices, raw seed sprouts, undercooked eggs (can transmits salmonella), undercooked or raw meats and seafood, or untreated water.
  • Do not touch animal feces that may spread germs that can lead to OIs. If you touch feces, be sure to wash your hands thoroughly with soap and water.

See Also


Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.