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Opportunistic Infections

Reviewed by: HU Medical Review Board | Last reviewed: September 2019

We are exposed to potentially infectious agents every day. However, our body’s immune system has many built-in defenses to protect us. This is why we aren’t constantly sick or have severe reactions to everything.

What are opportunistic infections?

An opportunistic infection is an infection that normally wouldn’t severely affect an individual with a healthy immune system, but can significantly affect someone who has a problem with their immune system or who has a weakened immune system. Individuals with a weakened immune system are considered to be “immunosuppressed”, meaning their immune system is not working to the best of its ability. Opportunistic infections can be bacterial (caused by bacteria), viral (caused by a virus), parasitic (caused by a parasite), or fungal (caused by a fungus).1

How are opportunistic infections related to HIV?

HIV infects cells in the body called CD4 cells (a type of T cell). CD4 cells are cells that are part of the immune system and help our bodies fight off infections and other foreign invaders. A normal CD4 count in a healthy individual can be anywhere from 500-1,500 cells/microliter; however, this number can be very low in individuals with advanced HIV.

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The lower an individual’s CD4 count, the weaker their immune system is and the more susceptible they are to infections. This is why individuals with HIV are at a higher risk of infection. Once CD4 counts get very low, normally non-infectious invaders can cause severe problems (opportunistic infections).1-6

Examples of opportunistic infections

As mentioned, opportunistic infections are infections that individuals with a healthy immune system would not normally be affected by (or would not be as severely affected by) in comparison to someone who is immunosuppressed.

Common infections that can be opportunistic and more severe in individuals with HIV include, but are not limited to:

  • Candidiasis (thrush) in the mouth, throat, lungs, or of the vagina
  • Herpes simplex virus (HSV) around the mouth, genitals, or anus
  • Salmonella in the gastrointestinal tract (gut)
  • Toxoplasmosis in the brain
  • Tuberculosis in the lungs (but can spread to other locations in the body)
  • Widespread fungal infections with fungi called cryptosporidiosis, histoplasmosis, and coccidioidomycosis
  • Widespread cytomegalovirus (CMV) including cytomegalovirus retinitis in the eye
  • Pneumonia (pneumocystis jirovecci pneumonia) in the lungs1,2

What are signs of an opportunistic infection

The signs of these infections are many of the same signs often associated with late-stage HIV (AIDS) since this is when an individual’s CD4 count is the lowest.

Several of these include, but are not limited to:

  • Recurring fever
  • Extreme tiredness
  • Rapid weight loss
  • Recurring night sweats
  • Long-term diarrhea
  • Pneumonia
  • Persistent cough
  • Long-term swelling of lymph nodes in the neck, groin, or armpits
  • Neurological issues such as depression or memory loss
  • Sores in or around the mouth, genitals, or anus
  • Purple, brown, red, or pink blotches inside the mouth or nose, under or on the skin, or around the eyelids2-6

Treatment of opportunistic infections

The treatment for an opportunistic infection depends on the cause of the infection. If an individual has thrush, a fungal infection, antifungal treatments are used. If the infection is bacterial, antibiotics are used. Antivirals may be used to treat some types of viruses. Past treatment history may also play a role in determining what medications may be used to fight an opportunistic infection. Additionally, some of these treatment options may be used on a regular basis to prevent an opportunistic infection from occurring in the first place, or from coming back.1

Prevention of opportunistic infections

The development and regular use of antiretroviral medications (ART) have decreased the frequency of opportunistic infections amongst people with HIV. Taking ART every day, exactly as prescribed, is an important step in preventing opportunistic infections.

Other prevention methods include typical infection-preventing behaviors, such as practicing regular hand washing, especially before eating or after going to the bathroom, keeping up to date with vaccinations, limiting time around individuals who are sick, cooking all meat, fish, and eggs or egg-containing products before eating them, washing fruits and vegetables thoroughly before eating, and drinking water from safe, clean sources (including when traveling).1