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What is an opportunistic infection?
Opportunistic infections (OIs) are infections that occur more often or are more severe in people with weakened immune systems than in people with healthy immune systems. People with weakened immune systems include people living with HIV or people receiving chemotherapy.
OIs are caused by a variety of germs (viruses, bacteria, fungi, and parasites). OI-causing germs can spread in the air; in saliva, semen, blood, urine, or feces (poop); or in contaminated food and water. Here are examples of common HIV-related OIs:
- Herpes simplex virus 1 (HSV-1) infection—a viral infection that can cause lesions (sores) on the mouth and face
- Salmonella infection—a bacterial infection that affects the intestines (the gut)
- Candidiasis (or thrush)—a fungal infection of the mouth, esophagus, or vagina
- Toxoplasmosis—a parasitic infection that can affect the brain
What are the most common opportunistic infection?
In the early years of the AIDS epidemic, OIs caused a lot of sickness and deaths. Once people started taking strong antiretroviral therapy (ART), however, a lot fewer people got OIs. It’s not clear how many people with HIV will get a specific OI.
In women, health problems in the vaginal area may be early signs of HIV. These can include pelvic inflammatory disease and bacterial vaginosis, among others. See fact sheet 610 for more information.
The most common OIs are listed here, along with the disease they usually cause, and the CD4 cell count when the disease becomes active:
- Candidiasis (Thrush) is a fungal infection of the mouth, throat, or vagina. CD4 cell range: can occur even with fairly high CD4 cells.
- Cytomegalovirus (CMV) is a viral infection that causes eye disease that can lead to blindness. CD4 cell range: under 50.
- Herpes simplex viruses can cause oral herpes (cold sores) or genital herpes. These are fairly common infections, but if you have HIV, the outbreaks can be much more frequent and more severe. They can occur at any CD4 cell count.
- Malaria is common in the developing world. It is more common and more severe in people with HIV infection.
- Mycobacterium avium complex (MAC or MAI) is a bacterial infection that can cause recurring fevers, general sick feelings, problems with digestion, and serious weight loss. CD4 cell range: under 50.
- Pneumocystis pneumonia (PCP) is a fungal infection that can cause a fatal pneumonia. CD4 cell range: under 200. Unfortunately, this is still a fairly common OI in people who have not been tested or treated for HIV.
- Toxoplasmosis (Toxo) is a protozoal infection of the brain. CD4 cell range: under 100.
- Tuberculosis (TB) is a bacterial infection that attacks the lungs, and can cause meningitis. CD4 cell range: Everyone with HIV who tests positive for exposure to TB should be treated.
Preventing opportunistic infection
The best ways to prevent getting an OI are to get into and stay on medical care and to take HIV medications as prescribed. Sometimes, your health care provider will also prescribe medications specifically to prevent certain OIs. By staying on HIV medications, you can keep the amount of HIV in your body as low as possible and keep your immune system healthy. It is especially important that you get regular check-ups and take all of your medications as prescribed by your care giver. Taking HIV medications is a life-long commitment.
In addition to taking HIV medications to keep your immune system strong, there are other steps you can take to prevent getting an OI.
- Use condoms consistently and correctly to prevent exposure to sexually transmitted infections.
- Don’t share drug injection equipment. Blood with hepatitis C in it can remain in syringes and needles after use and the infection can be transmitted to the next user.
- Get vaccinated your doctor can tell you what vaccines you need. If he or she doesn’t, you should ask.
- Understand what germs you are exposed to (such as tuberculosis or germs found in the stools, saliva, or on the skin of animals) and limit your exposure to them.
- Don’t consume certain foods, including undercooked eggs, unpasteurized (raw) milk and cheeses, unpasteurized fruit juices, or raw seed sprouts.
- Don’t drink untreated water such as water directly from lakes or rivers. Tap water in foreign countries is also often not safe. Use bottled water or water filters.
- Ask your doctor to review with you the other things you do at work, at home, and on vacation to make sure you aren’t exposed to an OI. For more information on international travel.
Diagnosis and Treatment
You can get lab tests to find out which germs are already in your body. This will help your doctor know how to treat you and which infections you should focus on preventing.
Keep a record of your symptoms, and pay attention to:
- Fever for more than 2 days
- Weight loss
- A change in vision
- Problems with your mouth, skin, or breathing
Call your doctor when you have new or unusual symptoms. Don’t wait for your next scheduled visit.
Because the HIV virus makes copies of itself more quickly when you have an opportunistic infection, early treatment is important. It will help you avoid the serious consequences of infection, as well as preserve your immune system.
Follow through with all of the treatment. Don’t quit early. Your doctor might also prescribe medication to prevent the infection from coming back, and if your immune system recovers, you may be able to stop taking that.