Opportunistic Infections

People with healthy immune systems can be exposed to certain viruses and have no reaction to them. But people living with HIV can face serious threats from opportunistic infections. These infections are called opportunistic because they take advantage of your weakened immune system, and they can still cause devistating illness. Antiretroviral therapy can help by increasing your number of CD4 cells, which will help protect you from OIS. You may also take medications used to prevent disease from occurring. (Prophylaxis)
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Opportunistic Infections and Their Relationship to HIV/AIDS

People with healthy immune systems can be exposed to certain viruses, bacteria, or parasites and have no reaction to them—but people living with HIV/AIDS can face serious health threats from what are known as “opportunistic” infections (OIs). These infections are called “opportunistic” because they take advantage of your weakened immune system, and they can cause devastating illnesses.

OIs are signs of a declining immune system. Most life-threatening OIs occur when your CD4 count is below 200 cells/mm3. OIs are the most common cause of death for people with HIV/AIDS.

The CDC developed a list of more than 20 OIs that are considered AIDS-defining conditions—if you have HIV and one or more of these OIs, you will be diagnosed with AIDS, no matter what your CD4 count happens to be:

  • Candidiasis of bronchi, trachea, esophagus, or lungs
  • Invasive cervical cancer
  • Coccidioidomycosis
  • Cryptococcosis
  • Cryptosporidiosis, chronic intestinal (greater than 1 month's duration)
  • Cytomegalovirus disease (particularly CMV retinitis)
  • Encephalopathy, HIV-related
  • Herpes simplex: chronic ulcer(s) (greater than 1 month's duration); or bronchitis, pneumonitis, or esophagitis
  • Histoplasmosis
  • Isosporiasis, chronic intestinal (greater than 1 month's duration)
  • Kaposi's sarcoma
  • Lymphoma, multiple forms
  • Mycobacterium avium complex
  • Tuberculosis
  • Pneumocystis carinii pneumonia
  • Pneumonia, recurrent
  • Progressive multifocal leukoencephalopathy
  • Salmonella septicemia, recurrent
  • Toxoplasmosis of brain
  • Wasting syndrome due to HIV

Because they can be so dangerous to your health, it is essential that you understand the signs, symptoms, prevention, and management of OIs.

Can I Prevent Opportunistic Infections?

One of the goals of HIV treatment is to lower your risk of getting OIs. Antiretroviral therapy can help by increasing your number of CD4 cells, which will help protect you from OIs. You may also take medications used to prevent disease from occurring (this is known as prophylaxis).

The Basics of Opportunistic Infections

OIs can occur all over the body and be relatively localized (meaning they affect only one part of the body) or systemic or disseminated (meaning they spread to other parts of the body and other body systems). Whether and when you become susceptible to OIs is often related to your CD4 count.

  • Greater than 500 cells/mm3
      • In general, people with CD4 counts greater than 500 cells/mm3 are not at risk for opportunistic infections. For people with CD4 counts around 500, however, the daily fluctuations in CD4 cell levels can leave them vulnerable to minor infections, such as candidal vaginitis or yeast infections.
  • 500 cells/mm3 to 200 cells/mm3
      • Candidiasis (Thrush)
        This is a fungal infection that is normally seen in patients with CD4 counts in this range. It is treatable with antifungal medications. A trained provider can usually diagnose thrush with a visual examination.

      • Kaposi’s Sarcoma (KS)
        KS is caused by Human Herpes Virus-8. Before the introduction of antiretroviral therapy, as many as 1 in 5 patients with AIDS had KS. It can cause lesions on the body and in the mouth. In addition, this virus can affect internal organs and disseminate to other parts of the body without any external signs. Treatment plans can include chemotherapy to shrink the lesions, as well as antiretroviral therapy to increase CD4 cell count. A diagnosis is typically made by inspecting a lesion and performing a direct biopsy on it.
      • Oral Symptoms include:
        • White patches on gums, tongue or lining of the mouth
        • Pain in the mouth or throat
        • Difficulty Swallowing
        • Loss of Appetite

        Vaginal Symptoms Include:
        • Vaginal Irritation
        • Itching
        • Burning
        • Thick, white discharge

        Signs and Symptoms of KS can include:
        • Appearance of a purplish lesion on skin
        • Appearance of a purplish lesion in the mouth
        • Occasionally gastrointestinal complaints with disseminated KS
  • 200 cells/mm3 to 100 cells/mm3
      • Pnuemocystis Jirovecii (Carinii) Pneumonia (PCP)
        PCP is a fungal infection and is the OI that most often causes death in patients with HIV. It is treatable with antibiotic therapy and close monitoring. If necessary, prophylaxis is available for patients who are at risk for PCP, but who are not ready to start antiretroviral medication. Diagnosing PCP usually involves a hospital stay to ensure proper testing and treatment without complications. For more information, see CDC’s You Can Prevent PCP.

        Histoplasmosis and Coccidioidomycosis
        These are fungal infections that are found in many regions of the United States. They often present as severe, disseminated illnesses in patients with low CD4 counts. Diagnosis consists of blood tests and evaluation for possible exposures related to geographical areas. For more information, see CDC’s Histoplasmosis or Coccidiodomycosis.

        Progressive Multifocal Leukoencephalopathy (PML)
        PML is a severe neurological condition that is caused by the JC virus and typically occurs in patients with CD4 counts below 200. While there is no definitive treatment for this disease, it has been shown to be responsive to antiretroviral therapy. In some cases, the disease resolves without any treatment. For more information, see the National Institute of Neurological Disorders and Stroke’s Progressive Multifocal Leukoencephalopathy Information Page.
      • Signs and Symptoms of PCP can include:
        • Shortness of Breath
        • Fever
        • Dry Cough
        • Chest Pain

        Signs and Symptoms of Histoplasmosis and Coccidioidomycosis can include:
        • Fever
        • Fatigue
        • Weight Loss
        • Cough
        • Chest pain
        • Shortness of Breath
        • Headache

        Signs and Symptoms of PML can include:
        • Dementia
        • Seizures
        • Difficulty Speaking
        • Confusion
        • Difficulty walking
  • 100 cells/mm3 to 50 cells/mm3
      • Toxoplasmosis
        Toxoplasmosis is caused by the parasite Toxoplasma gondii that can cause encephalitis and neurological disease in patients with low CD4 counts. The parasite is carried by cats, birds, and other animals and is also found in soil contaminated by cat feces and in meat, particularly pork. Toxoplasmosis is treatable with aggressive therapy, and prophylaxis is recommended for patients with low CD4 counts (usually less than 200). Diagnosis of this condition often requires imaging studies (CT or MRI) of the brain and a blood test. For more information, see CDC’s Toxoplasmosis and You Can Prevent Toxo.

        Cryptosporidiosis is a diarrheal disease caused by the protozoa Cryptosporidium, and it can become chronic for people with low CD4 counts. Symptoms include abdominal cramps and severe chronic diarrhea. Infection with this parasite can occur through: swallowing water that has been contaminated with fecal material (in swimming pools, lakes, or public water supplies); eating uncooked food (like oysters) that are infected; or by person-to-person transmission, including changing diapers or exposure to feces during sexual contact. Treatment and antiretroviral therapy are important. For more information, see CDC’s Cryptosporidiosis and You Can Prevent Cryptosporidiosis.

        Cryptococcal Infection or Cryptococcosis
        Cryptococcal infection is caused by a fungus thattypically enters the body through the lungs and can spread to the brain, causing cryptococcal meningitis. In some cases, it can also affect the skin, skeletal system, and urinary tract. This can be a very deadly infection if not caught and properly treated with antifungal medication. Although this infection is found primarily in the central nervous system, it can disseminate to other parts of the body, especially when a person has a CD4 count of less than 50. For more information, see CDC’s Cryptococcus (Cryptococcosis).
      • Signs and Symptoms of Toxoplasmosis can include:
        • Headache
        • Confusion
        • Motor Weakness
        • Fever
        • Seizures

        Signs and Symptoms of Cryptosporidiosis can include:
        • Chronic Watery Diarrhea
        • Stomach cramps
        • Weight loss
        • Nausea
        • Vomiting

        Signs and Symptoms of Cryptococcal Meningitis include:
        • Fever
        • Fatigue
        • Headache
        • Neck Stiffness
        • Some patients can have memory loss or mood changes
  • 50-100 Cells/mm3
      • Cytomegalovirus (CMV)
        CMV is an extremely common virus that is present in all parts of the world. It is estimated that a majority of the population have had CMV by the time they are 40 years-old. CMV can be transmitted by saliva, blood, semen and other bodily fluids. It can cause mild illnesses when first contracted and many people may never have symptoms. However, it does not leave the body when someone is infected with CMV. In patients with HIV and low CD4 counts it can cause infections in the eye and gastrointestinal system. For more information, see CDC's You can prevent CMV.
      • Signs and Symptoms of CMV:
        • Sore Throat
        • Swollen Glands
        • Fatigue
        • Fevers

        In people with low CD4 counts it can cause:
        • Blurred vision (if there is CMV infection is in the eye)
        • Painful Swallowing
        • Diarrhea
        • Abdominal Pain
  • Less than 50 Cells/mm3
      • Mycobaterium Aviam Complex (MAC)
        MAC is a type of bacteria that can be found in soil, water, and many places in the environment. These bacteria can cause disease in people with HIV and CD4 Counts less that 50. The bacteria can infect the lungs or the intestines, or in some cases, can become “disseminated”. This means that it can spread to the blood stream and other parts of the body. If this occurs, it can be a life threatening infection. If a persons CD4 count is below 50, then medications are available to prevent this infection from occurring. For more information, see CDC's You can prevent MAC.
      • Signs and Symptoms of MAC:
        • Fevers
        • Night sweats
        • Abdominal Pain
        • Fatigue
        • Diarrhea

Frequently Asked Questions

I noticed that some of the symptoms of opportunistic infections are similar to other things, like the flu. How do I know if I might have an OI or if it’s just the flu?

If you are concerned, check with your healthcare provider. There are some infections (pneumonia, sinus infections, skin infections, etc.) that can be associated with a weakened immune system--these will not get better until you get treatment. In general, if you are in good health, with a CD4 count above 400-500, you are not at risk for the more dangerous OIs. However, if you are unsure of your CD4 count, have had an OI before, or your symptoms worsen instead of improving over time, you should contact your care provider immediately.

Last revised: 11/16/2010