HIV and Opportunistic Infections, Coinfections, and Conditions

What is an STI?

STI stands for sexually transmitted infection. STIs are infections that spread from person to person through sexual activity, including anal, vaginal, or oral sex. STIs are caused by bacteria, parasites, and viruses.

STIs were previously known as sexually transmitted diseases. However, the phrase STI is more appropriate because a person with an infection may have no symptoms but still require treatment. When left untreated, an STI can become a disease.

HIV is one of many STIs, but it can progress to a disease called AIDS when it is not treated with HIV medicines. Other examples of STIs include chlamydia, gonorrhea, human papillomavirus (HPV) infection, and syphilis.

What is the connection between HIV and other STIs?

The same behaviors that increase the chances of getting HIV can also increase the chances of getting other STIs. These behaviors include the following:

• Having sex without a condom
• Having sex with many partners, especially anonymous partners
• Having sex while using drugs or alcohol, which can affect a person's judgment regarding safer sex practices

Having an STI can make it easier to get or transmit HIV. For example, an STI like herpes simplex virus can cause a sore or a break in the skin, which can make it easier for HIV to enter the body. Having HIV and another STI may increase the risk of HIV transmission.

How can a person reduce the risk of getting an STI?

Sexual abstinence (never having vaginal, anal, or oral sex) is the only way to fully eliminate the chance of getting an STI. However, the steps below can help reduce the likelihood of getting an STI, including HIV.

Choose Safer Sex Practices

• Use condoms correctly every time you have sex.
• Limit the number of partners with whom you have sex.
• Do not drink alcohol or use drugs before and during sex.
• Only have sex with people who get tested regularly.

Get Vaccinated

• Vaccines are available for certain STIs, like HPV and the hepatitis B virus. Vaccines are also available for other infections that could spread during close physical contact, such as mpox. Talk to a health care provider to learn more about vaccines for STIs.

Get Tested Regularly

• Although testing may not prevent STIs, for people who have sex regularly with more than one partner, getting tested regularly is the best way to identify and treat STIs before they progress to a more serious condition.

People without HIV can take additional steps to prevent HIV. Pre-exposure prophylaxis (PrEP) is an HIV prevention option for people who do not have HIV but who are more likely to get HIV. PrEP involves taking a specific HIV medicine on a regular dosing schedule to reduce the chance of getting HIV through sex or injection drug use. To learn more, read the HIVinfo Pre-Exposure Prophylaxis (PrEP) fact sheet.

People without HIV can also seek post-exposure prophylaxis (PEP) soon after a possible exposure to HIV to prevent getting HIV. Read the HIVinfo Post-Exposure Prophylaxis (PEP) fact sheet for more information.

How can a person with HIV prevent passing it to others?

Take HIV medicines as prescribed. Treatment with HIV medicines (called antiretroviral therapy or ART) helps people with HIV live long, healthy lives. One of the goals of ART is to reduce a person's viral load to an undetectable level. People with HIV who maintain an undetectable viral load have effectively no risk of sexually transmitting HIV to a partner who doesn’t have HIV.

If a person’s viral load is not undetectable—or does not stay undetectable—using condoms and practicing safer sex can help protect others from getting HIV. In addition, people without HIV can take medicine to prevent getting HIV.

What are the symptoms of STIs?

Symptoms of STIs can vary depending on the STI, and not everyone will experience the same symptoms. Examples of possible STI symptoms include painful urination (peeing), unusual discharge from the vagina or penis, or fever.

STIs may not always cause symptoms. Even if a person has no symptoms from an STI, it is still possible to pass the STI on to other people. For example, some people may never experience HIV symptoms but can transmit the virus to others about one month after getting HIV.

People who could benefit from STI prevention (and their partners) should talk to a health care provider about getting tested for STIs. To find STI information and testing sites near you, call CDC-INFO at 1-800-232-4636 or visit CDC's GetTested webpage.

What is the treatment for STIs?

STIs caused by bacteria or parasites can be cured with medicine. There is no cure for STIs caused by viruses, but treatment can relieve or eliminate symptoms and help keep the STI under control.

Treatment for viral STIs also reduces the chance of passing on the STI to a partner. For example, although there is no cure for HIV, HIV medicines can prevent HIV from advancing to AIDS and nearly eliminate the chances of HIV transmission when taken as prescribed.

Untreated STIs may lead to serious complications. For example, untreated gonorrhea in women can cause pelvic inflammatory disease, which may lead to infertility. Without treatment, HIV can gradually destroy the immune system and advance to AIDS.

Because some STIs can go unnoticed before they advance to a more serious condition, it is important for sexually active people to get tested.

This fact sheet is based on information from the following sources:

From CDC:

• About Sexually Transmitted Infections (STIs)
• Sexually Transmitted Infections (STIs)
• Substance Use and Sexual Risk Behaviors
• Preventing HIV
• Living With HIV

From the Eunice Kennedy Shriver National Institute of Child Health and Human Development:

• Sexually Transmitted Diseases (STDs)
• About Sexually Transmitted Diseases (STDs)

Also see the HIV Source collection of HIV links and resources.