(Last updated 6/14/2016; last reviewed 6/14/2016)
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:
Once a person is infected with HIV, the virus begins to multiply and to damage the immune system. A weakened immune system makes it harder for the body to fight off HIV-related OIs.
HIV medicines prevent HIV from damaging the immune system. But if a person with HIV does not take HIV medicines, HIV infection can gradually destroy the immune system and advance to AIDS. Many OIs, for example, certain forms of pneumonia and tuberculosis (TB), are considered AIDS-defining conditions. AIDS-defining conditions are infections and cancers that are life-threatening in people with HIV.
Before HIV medicines were available to treat HIV infection, OIs were the main cause of illness and death in people with HIV. HIV medicines are now widely used in the United States so fewer people with HIV get OIs. By preventing HIV from damaging the immune system, HIV medicines reduce the risk of OIs.
However, OIs are still a problem for many people with HIV. Some people with HIV get OIs for the following reasons:
For people with HIV, the best protection against OIs is to take HIV medicines every day.
People living with HIV can also take the following steps to reduce their risk of getting an OI.
Avoid contact with the germs that can cause OIs.
The germs that can cause OIs can spread in the feces of people and animals. To prevent OIs, don’t touch animal feces. Wash your hands with warm, soapy water after touching anything soiled with human feces, for example, a dirty diaper.
Ask your health care provider about other ways to avoid the germs that can cause OIs.
Be careful about what you eat and drink.
Food and water can be contaminated with OI-causing germs. To be safe, don’t eat or drink the following foods:
Only drink tap water or bottled water. Don’t drink water directly from a lake or river.
If you are visiting a foreign country, avoid eating food and drinking water that could make you sick. Before you travel, read this CDC fact sheet on travel abroad for people living with HIV.
Vaccines are products that protect people from diseases such as chicken pox, influenza (flu), and polio. Some vaccines can prevent HIV-related OIs. For example, people with HIV can get vaccinated to prevent pneumonia.
To learn more, read the AIDSinfo fact sheet on HIV and Immunizations.
There are many medicines to treat HIV-related OIs, including antiviral, antibiotic, and antifungal drugs. The type of medicine used depends on the OI.
Once an OI is successfully treated, a person may continue to use the same medicine or an additional medicine to prevent the OI from reoccurring (coming back).
The AIDSinfo Drug Database includes information on many of the medicines used to prevent and treat OIs.