Sexually transmitted diseases (STDs) are caused by sexually transmitted infections (STIs). They are usually transmitted during sexual activity through an exchange of bodily fluids or skin-to-skin contact where the infection is active. Non-sexual activities in which bodily fluids are exchanged can also transmit STIs

According to the World Health Organization (WHO), More than 1 million sexually transmitted infections (STIs) are acquired every day worldwide, the majority of which are asymptomatic.

In 2020, WHO estimated 374 million new infections with 1 of 4 STIs: chlamydia (129 million), gonorrhoea (82 million), syphilis (7.1 million) and trichomoniasis (156 million). More than 490 million people were estimated to be living with genital herpes in 2016, and an estimated 300 million women have an HPV infection, the primary cause of cervical cancer and anal cancer among men who have sex with men. An estimated 296 million people are living with chronic hepatitis B globally.

STIs are caused by bacteria, viruses or parasites. A sexually transmitted infection may pass from person to person in blood, semen, or vaginal and other bodily fluids.

Sometimes sexually transmitted infections are spread in ways other than sexual contact. For example, STIs can spread to infants during pregnancy or childbirth. STIs also can spread through blood transfusions or shared needles

An infection which is when bacteria, viruses, or parasites attack the body comes before a disease.

And while an infection may result in zero symptoms, a disease usually always comes with clear signs.

STD symptoms

Many people in the early stages of an STD have no symptoms. That’s why screening is important to prevent complications

If an STD starts with a symptomatic STI, you might first experience:

• pain or discomfort during sexual activity or urination
• sores, bumps, or rashes on or around the vagina, penis, testicles, anus, buttocks, thighs, or mouth
• unusual discharge or bleeding from the penis or vagina
• painful or swollen testicles
• itchiness in or around the vagina
• unexpected periods or bleeding after sexual activity

But remember that not all STIs have symptoms.

If an STI progresses to an STD, symptoms can vary. Some of them may be similar to the above, such as pain during sexual activity, pain during urination, and irregular or painful periods.

But other symptoms can be quite different and depend on the STD. They can include:

• fever
• recurring pain
• fatigue
• memory loss
• changes to vision or hearing
• nausea
• weight loss
• lumps or swellings

Underlying STD causes

All STDs are caused by an STI.

These infections are usually transmitted through sexual contact, including through bodily fluids or skin contact via vaginal, oral, and anal sex.

Some of them never become a disease, especially if they’re treated, and they can even go away on their own.

But if the pathogens that caused the infection end up damaging cells in the body and disrupting its functions, an STI will progress to an STD.

Types of STDs

While the list of STIs is pretty lengthy, there are fewer STDs.

They range from pelvic inflammatory disease (PID), caused by STIs like chlamydia and gonorrhea, to some forms of cancer, caused by human papillomavirus (HPV).

Pelvic inflammatory disease

Gonorrhea, chlamydia, and trichomoniasis are common STIs that can lead to PIDTrusted Source if left untreated.

But not all cases of PID are caused by an STI, as other bacterial infections can play a role.

Around 2.5 million womenTrusted Source in the United States have a reported lifetime history of being diagnosed with PID, according to the Centers for Disease Control and Prevention (CDC).

Although this infection of the female reproductive organs is classified as a disease, some people have no symptoms.

Those who do have symptoms may experience:

• pelvic or lower abdominal pain
• pain during penetrative vaginal sex or when urinating
• irregular, heavy, or painful vaginal bleeding
• unusual vaginal discharge
• nausea
• high temperature

Antibiotics can successfully treat PID if it’s diagnosed early enough. However, they won’t treat any scarring on the fallopian tubes that may have occurred.

This scarring can make an ectopic pregnancy more likely and has also been linked to infertility, with around 1 in 10 people with PID becoming infertile as a result.

Tertiary syphilis

The early stages of syphilis a relatively uncommon infection are considered an STI.

The infection first appears as one or more small round sores on the genitals, anus, or mouth. If left untreated, syphilis will move to the latent phase, which has no symptomsTrusted Source.

However, around a quarter of people will go on to develop tertiary syphilis from here 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:

• loss of vision
• loss of hearing
• memory loss
• mental health conditions
• infections of the brain or spinal cord
• heart disease

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.

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

Cancer

Although some strains of HPV tend to cause no disease, other strains can cause abnormal cell changes.

This can lead to cancer, including:

• oral cancer
• cervical cancer
• vulvar cancer
• penile cancer
• anal cancer

HPV causes almost all cervical cancers, as well as over 90% of anal cancers, 75% of vaginal cancers, and over 60% of penile cancers.

Symptoms of these cancers vary, depending on where in the body they affect. Swellings and lumps, bleeding, and pain can be common.

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

Some screening tests exist to detect pre-cancerous cell changes caused by HPV.

Genital warts

Some lower-risk strains of HPV can cause a disease called genital warts.

These skin-colored or white bumps show up on the genitals or anus, with over 350,000 people developing them every year.

They are treatable, but not curable, as the virus that causes them may remain. (In some cases, HPV disappears on its own.)

Genital warts can also go away by themselves, but they can also come back.

If you want to get them removed, options range from freezing or burning them off to applying a chemical cream or liquid.

AIDS

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 lead to AIDS, where the body becomes vulnerable to serious infections and illnesses.

People with AIDS may experience:

• rapid weight loss
• extreme fatigue
• sores
• infections
• neurologic disorders
• cancers

No cure is available for AIDS. And due to the variety of diseases that can be contracted as a result of a severely weakened immune system, life expectancy without treatment is around 3 years

Tips for STD prevention

The best way to avoid an STD is to prevent STIs. And the only foolproof way to do that is to avoid sexual contact.

But there are ways to make sex safer and reduce the risk of contracting an STI:

• Have an open discussion about sexual history with a new partner before engaging in any sexual activity, and decide what you’re each comfortable with.
• Get tested regularly for STIs, especially if you have a new partner or multiple partners. Ask any partners to do the same.
• Use a condom properly during vaginal, anal, and oral sex to help prevent STIs that spread through fluids. Dental dams can also provide protection during oral sex.
• Consider getting vaccinated for HPV and hepatitis B.
• If you’re at a higher risk for contracting HIV, think about taking PrEP medication every day.

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