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Patient education: Preventing opportunistic infections in HIV (Beyond the Basics)

John G Bartlett, MD
Paul E Sax, MD
Section Editor
Martin S Hirsch, MD
Deputy Editor
Jennifer Mitty, MD, MPH
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Infection with HIV reduces the immune system's ability to fight infections. Certain bacteria, viruses, fungi, and other organisms, which do not usually cause infections in healthy people, can cause infections in people with a weakened immune system; these are called "opportunistic" infections. One way to measure the strength of the immune system of a patient with HIV is to measure the T cell count (also called the CD4 count). When the T cell count is below 200 cells/microL, the patient has developed AIDS and is at risk for opportunistic infections. However, many opportunistic infections can be prevented by taking certain antibiotics and antifungal medications. HIV medications can also boost the T cell count, so the risk of opportunistic infections declines with ongoing treatment. An explanation of T cell counts is available separately. (See "Patient education: Initial treatment of HIV (Beyond the Basics)".)

Other topic reviews about the treatment of HIV are available separately. (See "Patient education: Initial treatment of HIV (Beyond the Basics)" and "Patient education: Tips for taking HIV medications (Beyond the Basics)".)


Specific treatments to prevent opportunistic infections are recommended in the following cases:

HIV-infected people with a T cell count <200 cells/microL to prevent pneumocystis pneumonia (PCP).

HIV-infected people with a T cell count <150 cells/microL who live in areas where there are a large number of cases of histoplasmosis.

HIV-infected people with a T cell count <100 cells/microL who have a positive blood test for Toxoplasma to prevent reactivation of this infection.

HIV-infected people with a positive skin or blood test for tuberculosis, regardless of CD4 cell count.

More detailed information about these situations, as well as other infections that can affect people with HIV, is below.


Although the best way to prevent opportunistic infections is to improve your immune system, certain infections can be prevented by taking antibacterial or antifungal medications. In most cases, these medications can be discontinued after your immune system has significantly improved for at least 3 months.

Pneumocystis — Pneumocystis (pronounced new-mow-SIS-tis) jirovecii pneumonia (formerly called Pneumocystis carinii pneumonia or PCP) is an opportunistic infection of the lungs. It is the leading AIDS-related cause of pneumonia and death. It is possible to prevent most cases of PCP by taking an antibiotic.

Preventive treatment is very effective in preventing this type of pneumonia, and it is strongly recommended for people with a low T cell count (usually less than 200 cells/microL), a history of PCP pneumonia, or a history of thrush (a yeast infection in the mouth).

People who begin antiretroviral therapy for HIV may discontinue PCP preventive therapy when their T cell count is greater than 200 cells/microL for at least three months. However, lifelong preventive treatment may be recommended for people who developed PCP when the T cell count was greater than 200 cells/microL.

Histoplasmosis — Histoplasma is a fungus that grows in soil and areas contaminated with bat or bird droppings; it is more common in certain areas, such as the Mississippi, Ohio, and St. Lawrence River valleys, the Caribbean, southern Mexico, and certain parts of Central and South America, Africa, and Asia. It can cause pneumonia in people with HIV who have a low T cell count and who live in an area where there is a high risk of infection.

People who visit or live in these areas should avoid high risk activities, such as disturbing soil under bird roosting sites, demolishing old buildings, or exploring caves.

A preventive antifungal treatment may be recommended to people who have a low T cell count (generally less than 150 cells/microL) who are at high risk of becoming infected; this would include people who live in areas where the infection is common.

Toxoplasma — Toxoplasmosis is an infection that is found worldwide and usually causes infection without any major symptoms. However, the parasite persists in the body and can cause a life-threatening infection in the brain in people with AIDS. A blood test is recommended after HIV is diagnosed to determine if a person has been exposed to the Toxoplasma parasite previously. Preventive treatment is recommended if the T cell count is less than 100 cells/microL. Certain antibiotics used to prevent PCP can also prevent toxoplasmosis.

If the blood test shows that the patient has never had toxoplasmosis infection in the past, it is important to avoid exposure. Common sources of the parasite include raw or rare meats (in particular lamb, beef, pork, or venison), cat stool, and soil.

If an HIV-infected person has not previously been exposed to Toxoplasma, measures to prevent infection are sometimes recommended, including the following:

Do not eat raw or rare lamb, beef, pork, or venison. Meat that is pink inside indicates that the meat is not adequately cooked; the internal temperature should be at least 165ºF.

Avoid changing cat litter; if someone cannot assist you, use gloves and wash hands when finished. Avoid touching stray cats.

Wash hands after gardening.

Wash hands and counter tops after preparing raw meat or poultry.

Wash fruits and vegetables well before eating them raw.

Mycobacterium avium complex (MAC) — Mycobacterium avium complex (MAC) is an opportunistic infection that can develop in people with HIV who have T cell counts below 50 cells/microL. MAC can cause high fevers, abdominal pain, and weight loss.

Mycobacterium avium can be found throughout the environment; it is not possible to prevent infection through personal protective measures. Certain antibiotics can help reduce the risk of developing MAC infection, and in the past, an antibiotic was given to people with HIV when their T cell count was less than 50 cells/microL. However, many providers no longer routinely prescribe antibiotics to prevent MAC infection in people who are initiating antiretroviral therapy for HIV. If antibiotic treatment was already started, it can generally be stopped when the person's T cell count is greater than 100 cells/microL for at least three months.

Candida (yeast) — Candida (yeast) infections of the mouth and vagina are more common in people with HIV. Yeast infections can also develop in other areas, such as in skin folds, in the groin, and around the anus.

Preventive treatments for candida are not usually recommended unless you have frequent infections. Yeast infections in women are discussed in detail in a separate topic review. (See "Patient education: Vaginal yeast infection (Beyond the Basics)".)

Cryptococcus — Cryptococcus is a fungus that is found in the environment, particularly in soil frequented by birds. Infection with this fungus can lead to a lung infection called cryptococcosis (pronounced crip-toe-cah-COH-sis) and/or a severe brain infection (called cryptococcal meningitis). This infection is more common in people with a T cell count less than 100 cells/microL.

Cryptococcal infection is the fourth most common opportunistic infection in people with AIDS. The number of cases of cryptococcosis has declined since effective antiretroviral treatments (ART) became available, although this infection is still a relatively common AIDS-defining illness in people who do not take HIV medications.

Treatments to prevent cryptococcosis are not recommended because they have not been shown to improve survival.

Coccidioides — Coccidioides is a fungus that can cause an infection, called coccidioidomycosis (pronounced cox-SID-ee-oh-doe-my-coe-sis). The most common type of coccidioidomycosis is a type of pneumonia known as Valley Fever. People who are infected with HIV are at risk for a serious body-wide coccidioidomycosis infection, known as disseminated coccidioidomycosis.

The majority of cases of coccidioidomycosis in the United States occur in the southwestern part of the country, primarily Arizona and California. The fungus is normally found in the soil, and most people become infected after inhaling spores of the fungus.

Treatments to prevent infection with Coccidioides are not usually recommended because they have not been shown to improve survival. However, people with HIV who live in areas where the fungus is common are advised to stay indoors during dust storms and to avoid activities that could expose them to dust or desert soil (eg, construction work, farming, gardening).

People who are HIV-positive who become infected with Coccidioides are generally treated as soon as possible with an antifungal medication; this can reduce the risk of developing serious complications.

Cytomegalovirus — Cytomegalovirus (CMV) is a virus that commonly causes infection in persons worldwide. CMV can lead to a mild illness with fever and body aches, but most of the time, this infection does not cause any symptoms.

However, CMV persists in the body, and in a patient with AIDS, CMV can lead to disease in the eyes, digestive system, brain, and spinal cord. Infection of the eye (retina) is the most common opportunistic CMV infection and can cause blurring and progressive loss of vision, and even blindness in people with AIDS.

Past exposure to CMV infection is common, with approximately 50 percent of the adults in the United States having been exposed at some point during their life. If a blood test in an HIV-infected patient demonstrates past infection, a routine eye examination should be done to look at the retina in people with T cell counts less than 250 cells/microL, whether or not they have any eye symptoms.

Treatment to prevent infection with CMV is not usually recommended because this has not been shown to improve survival. However, anyone with early signs of CMV retinitis (eg, blurry vision, blind spots, flashing lights, or floaters) should contact their healthcare provider immediately because treatment for this condition is effective if given promptly.

Cryptosporidium — Cryptosporidium (pronounced crip-toe-spore-ID-ee-um) is a parasite that can infect people who consume contaminated drinking and swimming water. The parasite can also be spread through contact with feces from infected pets or humans. Infection with the parasite is called cryptosporidiosis, and is a common cause of diarrhea in people with HIV.

All people are susceptible to infection, but HIV-infected persons with T counts less than 100 cells/microL can have an unusually severe and prolonged illness. To reduce the risk of infection, HIV infected people should wash hands after diaper changing or contact with pets or soil. Close contact with people who are infected with cryptosporidium should be avoided. During outbreaks that are thought to be related to contamination of the municipal water supply, drinking bottled water or boiling tap water can reduce the risk of becoming infected.

There is no proven preventive treatment for Cryptosporidium. However, the preventive antibiotics used for Mycobacterium avium complex (MAC) may protect against cryptosporidial infection. Symptoms of infection usually resolve when T cells are boosted with HIV medications.

Streptococcus pneumoniae — People with HIV infection are at increased risk of developing infection (such as pneumonia) caused by the bacteria Streptococcus pneumoniae. Vaccines are recommended to prevent this infection. There are 2 types of pneumococcal vaccines, and people with HIV should get one of each type.

Tuberculosis — Tuberculosis (TB) is a disease caused by the bacteria Mycobacterium tuberculosis. It most commonly affects the lungs, although it can affect other parts of the body. Some people are exposed to TB but do not have an active infection (this is called "latent tuberculosis infection," or LTBI). People with LTBI should be treated with a medication or medications to kill the latent bacteria and prevent active TB later in life. (See "Patient education: Tuberculosis (Beyond the Basics)".)


Preventive treatment for Pneumocystis pneumonia and toxoplasmosis is usually discontinued when the T cell count is >200 cells/microL for three months.

If preventive treatment for Mycobacterium avium complex was started, it is usually discontinued when the T cell count is >100 cells/microL for three months.


Treatments to prevent opportunistic infections are recommended for some people with HIV, especially when the T cell count is low. The risk of each infection varies by the T cell count. Although the best type of prevention is recovery of the immune system through the use of antiretroviral therapy, certain antibacterial and antifungal medications can help prevent infection in people with CD4 cell counts less than 200 cells/microL. These medications can usually be stopped when the immune system has sufficiently improved.


Your healthcare provider is the best source of information for questions and concerns related to your medical problem.

This article will be updated as needed on our web site (www.uptodate.com/patients). Related topics for patients, as well as selected articles written for healthcare professionals, are also available. Some of the most relevant are listed below.

Patient level information — UpToDate offers two types of patient education materials.

The Basics — The Basics patient education pieces answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials.

Patient education: HIV/AIDS (The Basics)
Patient education: Vaccines for adults with HIV (The Basics)
Patient education: Pneumocystis pneumonia (PCP) (The Basics)

Beyond the Basics — Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are best for patients who want in-depth information and are comfortable with some medical jargon.

Patient education: Initial treatment of HIV (Beyond the Basics)
Patient education: Tips for taking HIV medications (Beyond the Basics)
Patient education: Vaginal yeast infection (Beyond the Basics)

Professional level information — Professional level articles are designed to keep doctors and other health professionals up-to-date on the latest medical findings. These articles are thorough, long, and complex, and they contain multiple references to the research on which they are based. Professional level articles are best for people who are comfortable with a lot of medical terminology and who want to read the same materials their doctors are reading.

Approach to the HIV-infected patient with pulmonary symptoms
Cryptococcus neoformans infection outside the central nervous system
Diagnosis and treatment of disseminated histoplasmosis in HIV-uninfected patients
Diagnosis and treatment of pulmonary histoplasmosis
Immune reconstitution inflammatory syndrome
Immunizations in HIV-infected patients
Mycobacterium avium complex (MAC) infections in HIV-infected patients
Overview of Candida infections
Overview of prevention of opportunistic infections in HIV-infected patients
Pneumococcal immunization in HIV-infected adults
Toxoplasmosis in HIV-infected patients
Treatment of AIDS-related cytomegalovirus retinitis
Treatment and prevention of Pneumocystis infection in HIV-infected patients

The following organizations also provide reliable health information.

Centers for Disease Control and Prevention (CDC)

     Toll-free: (800) 311-3435

CDC (Centers for Disease Control and Prevention) National AIDS Hotline

     English: (800) 342-2437
     Spanish: (800) 344-7432

National Institute of Allergy and Infectious Diseases (NIAID)


HIV/AIDS Treatment Information Service

     Toll-free: (800) 448-0440

AIDS Clinical Trials Information Service (ACTIS)

     Toll-free: (800) 874-2572

Patient support — There are a number of online resources where patients can find information and support:

The Body: The Complete HIV/AIDS Resource

AIDSinfo: Understanding HIV/AIDS



Literature review current through: Nov 2017. | This topic last updated: Thu Nov 16 00:00:00 GMT+00:00 2017.
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  1. Kovacs JA, Masur H. Prophylaxis against opportunistic infections in patients with human immunodeficiency virus infection. N Engl J Med 2000; 342:1416.
  2. Panel on Opportunistic Infections in HIV-Infected Adults and Adolescents. Guidelines for the prevention and treatment of opportunistic infections in HIV-infected adults and adolescents: recommendations from the Centers for Disease Control and Prevention, the National Institutes of Health, and the HIV Medical Association of the Infectious Diseases Society of America. Updated May 7, 2013. http://aidsinfo.nih.gov/contentfiles/lvguidelines/adult_oi.pdf (Accessed on July 29, 2013).

All topics are updated as new information becomes available. Our peer review process typically takes one to six weeks depending on the issue.