HIV and Opportunistic Infections: What They Are and How to Prevent Them

HIV weakens the body's immune system by destroying the white blood cells that fight infection. That leaves people with HIV open to opportunistic infections (OIs): infections that occur more often, or are more severe, in people with weakened immune systems than in people with healthy ones. Others with weakened immunity — people with cancer, or who have had organ transplants — face them too.

Kinds of opportunistic infection

OIs are caused by viruses, bacteria, fungi and parasites, spread in many ways — through the air, body fluids, or contaminated food or water. MedlinePlus lists:

NIH's HIVinfo adds candidiasis and Salmonella infection. Sometimes an inactive infection, such as latent tuberculosis, becomes active as the immune system weakens. Many OIs — certain forms of pneumonia and TB among them — and some cancers are "AIDS-defining conditions," which are life-threatening in people with HIV.

HIV can also make infections harder to treat, and people with HIV are more likely to have complications from common illnesses such as the flu.

Why they still happen

Without treatment, HIV multiplies, damages the immune system and can gradually destroy it, progressing to AIDS. HIV medicines prevent that damage. Because they are widely used in the United States, OIs are less common than they once were, but they still affect many people with HIV, usually because:

• they don't know they have HIV and so are not being treated — an OI may be the first sign;
• they know they have HIV but are not getting treatment;
• they are being treated, but the medicines are not controlling their HIV.

Prevention

The best protection is to take HIV medicines exactly as prescribed and to keep follow-up appointments, to make sure the treatment is working. Other steps help too:

• practise safe sex — use condoms every time;
• wash your hands well and often;
• cook food thoroughly.

Detailed guidance is in the federal Guidelines for the Prevention and Treatment of Opportunistic Infections in Adults and Adolescents With HIV.

Sources

• MedlinePlus, U.S. National Library of Medicine, "HIV and Infections." https://medlineplus.gov/hivandinfections.html
• HIVinfo, National Institutes of Health, "What is an Opportunistic Infection?" (last reviewed March 31, 2025), used for the definition, how OIs spread, further examples, AIDS-defining conditions, why OIs still occur and the role of follow-up care: https://hivinfo.nih.gov/understanding-hiv/fact-sheets/what-opportunistic-infection
• Rewritten in hubnx's own words.