Some sexually transmitted infections (STIs) can lead to pelvic inflammatory disease (PID), anal or genital warts, and certain cancers.

All STDs are caused by an STI. STIs are usually transmitted through genital fluids or skin-to-skin contact during anal, oral, or vaginal sex.

Many infections do not become diseases, especially with prompt diagnosis and treatment. STDs occur when the pathogens that cause the infection begin to damage cells and disrupt bodily functions.

This article will focus on conditions that you may not necessarily associate with sexual activity.

PID occurs when bacteria in the vagina or cervix move up into the uterus, ovaries, or fallopian tubes. It’s typically caused by undiagnosed or untreated gonorrhea and chlamydia.

PID is also linked to bacterial vaginosis, a vaginal infection that’s more common among people who are sexually active.

Symptoms of PID may include:

Oral, intravenous (IV), or injection antibiotics are often the first course of treatment. Although antibiotics can cure the underlying infection, surgery may be needed to remove any abscesses that have formed.

The longer that PID goes untreated, the more likely scarring is to occur. Scarring is irreversible and increases the risk of chronic pelvic pain, ectopic pregnancy, and infertility.

Some strains of HPV can cause internal or external warts. A single bump or group of bumps may form:

  • on the vulva or around the vaginal opening
  • inside the vaginal canal or on the cervix
  • on the tip or along the shaft of the penis
  • on the scrotum
  • between the genitals and the anus (perineum)
  • in or around the anal opening

Warts may be:

  • darker than the surrounding skin, skin-colored, red, or whitish
  • itchy or irritated
  • raised or flat
  • soft or firm

Warts inside the vagina or rectum can also cause unexpected bleeding or discharge.

In some cases, warts may clear within 6 months without medical intervention. However, warts can come back until your body clears the underlying virus.

A healthcare professional may recommend a topical treatment, cryotherapy, or surgery to remove persistent or recurrent warts.

Some strains of HPV can cause abnormal cell changes that become cancerous over time. According to the National Cancer Institute, HPV is responsible for:

You may be more likely to develop HPV-related cancer if you have a weakened immune system, smoke cigarettes, vape fluids with nicotine, or use other tobacco products.

Talk with a healthcare professional about your individual risk for HPV and related cancers. If you’re at risk for cervical cancer, they may recommend more frequent pap smears or HPV tests.

There aren’t standardized screening measures for other cancers, so your healthcare professional may help you develop a personalized schedule. Digital rectal exams and anal pap smears, for example, can help detect changes.

If cancer is diagnosed early, it’s often easier to treat with chemotherapy, radiation, or surgery.

An estimated 25% to 40% of untreated syphilis cases progress to this stage — a process that can take between 10 and 30 years after the initial infection.

This disease can have serious consequences for several organ systems in the body, leading to:

The earlier syphilis is diagnosed and treated, the less damage it does.

While penicillin injections are typically used to treat tertiary syphilis and remove the bacteria from the body, they can’t reverse any damage that’s already occurred.

If the disease causes problems with major organs, like the heart, other medications and procedures may be required.

HIV can damage the immune system and increase the risk of contracting other viruses or bacteria and developing certain cancers.

With today’s treatments, many people with HIV live long, healthy lives. But if left untreated, the virus can progress to stage 3, where the body becomes vulnerable to serious infections and illnesses.

You may experience:

The best way to reduce your risk is to practice safer sex. You can:

Many STDs are treatable, but not all of them are curable. Some can be life threatening, while others have less serious effects.

They are, however, all caused by an STI. So the best way to prevent them is to get regularly screened and practice safer sex. And if you test positive for any STI, seek treatment as soon as possible.