8 Common STIs: Symptoms, How They Spread & How to Prevent Them

Sexually transmitted infections are common, but confusion about them is even more common.

Can you catch an STI from oral sex? Can someone have one without symptoms? Does using a condom protect against every infection? And which STIs can actually be cured?

There are more than 30 bacteria, viruses, and parasites known to be transmitted through sexual contact. This guide covers eight of the best-known infections, including their symptoms, how they spread, and how to reduce your risk. (WHO: Sexually transmitted infections)

First, remember this. No symptoms does not mean no infection. Someone can have an STI and pass it on without knowing it. Testing is much more reliable than trying to guess from appearances. You cannot look at someone and tell whether they have an STI. You just can't.
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Chlamydia

Chlamydia is a bacterial STI that can infect the genitals, rectum, and throat.

Possible symptoms are often none. When symptoms do occur, they may include unusual vaginal or penile discharge, burning when urinating, pelvic pain, or testicular pain. Untreated infection can cause complications, including infertility.

It spreads through vaginal, anal, or oral sex with an infected partner.

How to prevent it? Use condoms correctly, get tested when recommended, and make sure infected partners receive treatment. Chlamydia is curable with appropriate antibiotics. (CDC: Chlamydia)

The tricky part about chlamydia is that it's often silent. You can have it for months without knowing. That's why regular testing matters, especially if you have new or multiple partners.

Gonorrhea

Gonorrhea is a bacterial STI sometimes nicknamed the clap. It can infect the genitals, rectum, and throat.

Possible symptoms are often none, particularly in women and in throat or rectal infections. Symptoms may include burning during urination, yellow or green penile discharge, increased vaginal discharge, bleeding between periods, or rectal pain and discharge.

It spreads through vaginal, anal, or oral sex with an infected person.

How to prevent it? Use condoms, test when recommended, and ensure partners receive appropriate treatment. Gonorrhea is treatable, but antibiotic resistance is making some infections harder to treat. Never self-prescribe leftover antibiotics. That's a recipe for disaster. (CDC: Gonorrhea)

Syphilis

Syphilis is a bacterial STI that progresses through stages if left untreated and can eventually damage the brain, nerves, heart, and other organs.

Possible symptoms include an early sign that can be a firm, usually painless sore around the genitals, anus, or mouth. Later symptoms may include a rash, sometimes on the palms of the hands and soles of the feet, swollen lymph nodes, fever, or fatigue. Symptoms can disappear even while infection remains.

It spreads through direct contact with an infectious sore during vaginal, anal, or oral sex. It can also pass from a pregnant person to their baby.

How to prevent it? Condoms reduce risk, but sores can occur on skin they don't cover. Testing and prompt antibiotic treatment are important. Syphilis is curable with appropriate treatment. (CDC: Syphilis)

Syphilis is sometimes called the great imitator because its symptoms can look like so many other things. That's why testing is so important if you have any reason to suspect exposure.

Genital Herpes (HSV-1 and HSV-2)

Genital herpes is a viral infection that can cause oral or genital herpes. HSV-1, often associated with cold sores, can also cause genital herpes.

Possible symptoms include many people having no symptoms or only mild ones. Others develop clusters of blisters that break into painful sores, itching, tingling, or flu-like symptoms during an initial outbreak.

It spreads through direct oral, genital, or anal skin contact, including contact with infected areas when no visible sores are present. Oral herpes can spread to the genitals through oral sex.

How to prevent it? Avoid sexual contact during outbreaks, use condoms or barriers, and discuss treatment with a healthcare professional. These measures reduce risk but cannot eliminate it entirely. Antiviral medicines can control outbreaks and reduce transmission risk. Herpes currently has no cure. (CDC: Genital herpes)

Here's the thing about herpes. Most people who have it don't know they have it. And you can pass it on even when you don't have any visible sores. That's not meant to scare you. It's meant to inform you. Knowing your status is power.

Human Papillomavirus (HPV)

HPV is a large family of viruses. Some types cause genital warts. Others can cause cancers, including cervical, anal, penile, and certain throat cancers.

Possible symptoms are usually none. Some types cause genital warts, while cancer-associated HPV infections can persist for years without obvious symptoms.

It spreads through intimate genital skin-to-skin contact and vaginal or anal sex. Transmission can occur without penetration.

How to prevent it? HPV vaccination is one of the most effective preventive measures. Condoms reduce risk but cannot cover every area of potentially infected skin. Follow recommended cervical screening guidelines if you have a cervix. Most HPV infections clear naturally, but not all do. (CDC: Genital HPV)

The HPV vaccine is a game-changer. If you're eligible and haven't gotten it, talk to your doctor. It prevents the types of HPV most likely to cause cancer.

Trichomoniasis

Trichomoniasis is a common STI caused by a tiny parasite, often shortened to trich.

Possible symptoms include most infected people having no symptoms. Others may experience genital itching, burning during urination, discomfort during sex, or unusual vaginal discharge that may smell different or appear yellow-green. Men can also become infected, often without noticeable symptoms.

It spreads mainly through sexual contact involving infected genital areas, commonly penis-to-vagina or vagina-to-vagina sex.

How to prevent it? Condoms help reduce transmission. Testing and prescription treatment are important, and current partners generally need treatment too to prevent reinfection. Trichomoniasis is curable with appropriate medication. (CDC: Trichomoniasis)

HIV

HIV is a virus that attacks the immune system. Without treatment, it can progress to AIDS, the most advanced stage of HIV infection.

Possible symptoms include some people developing flu-like symptoms within weeks of infection, such as fever, rash, sore throat, and swollen lymph nodes. Others have no noticeable symptoms for years.

It spreads through certain body fluids, including blood, semen, pre-seminal fluid, rectal fluids, and vaginal fluids, which must reach susceptible tissue or enter the bloodstream. Sexual transmission primarily occurs through vaginal or anal sex. Sharing contaminated injection equipment is another route.

How to prevent it? Use condoms, consider PrEP if you may be exposed, and seek PEP urgently after a possible exposure. PEP must be started within 72 hours. HIV has no current cure, but effective treatment allows people to live long, healthy lives.

An especially important fact is that a person taking HIV treatment who maintains an undetectable viral load does not transmit HIV through sex. This is known as U=U: Undetectable equals Untransmittable. (CDC: HIV prevention) (CDC: PEP and HIV risk reduction)

U=U is one of the most important breakthroughs in HIV prevention. It means that people living with HIV who are on effective treatment can have sex without fear of passing the virus to their partners. That's huge.

Hepatitis B

Hepatitis B is a viral infection that attacks the liver. It can be short-term or become chronic, potentially causing cirrhosis and liver cancer.

Possible symptoms include many people having none. Symptoms can include fatigue, nausea, abdominal discomfort, dark urine, pale stools, and yellowing of the skin or eyes.

It spreads through infected blood, semen, and certain other body fluids, including during sex. It can also pass from an infected mother to her baby at birth.

How to prevent it? Get vaccinated. The hepatitis B vaccine is a highly effective prevention method. Condoms reduce sexual transmission risk, and testing is important because chronic infection can remain unnoticed. Chronic hepatitis B can be managed with medical care, although not everyone clears the virus completely. (CDC: Hepatitis B prevention)

How to Protect Yourself From STIs

You do not need to be afraid of sex. You need accurate information and a prevention plan that fits your life.

Use condoms and barriers correctly. External or internal condoms reduce the risk of many STIs during vaginal and anal sex. Condoms and barriers also reduce risk during oral sex, although protection varies by infection. They are less effective against infections spread through uncovered skin, such as herpes, HPV, and some syphilis sores.

Get tested instead of guessing. Testing recommendations depend on your age, sexual activities, partners, and local guidelines. Depending on your exposure, testing may involve urine, blood, or swabs from genital, throat, or rectal sites.

Consider vaccination. HPV and hepatitis B vaccines prevent important sexually transmitted infections and related health problems. Ask a healthcare professional which vaccines you need.

Talk openly with partners. Discuss recent testing, protection, and any diagnosis. A person can look and feel perfectly healthy while carrying an STI.

Get treatment and prevent reinfection. Many bacterial and parasitic STIs are curable. If you test positive, follow the treatment instructions, notify relevant partners, and avoid sexual contact for the period recommended by your healthcare professional. (CDC: STI prevention and testing)

When Should You Get Tested?

Consider an STI test if you have had sex without a barrier with a new or untested partner, learn that a partner has an STI, develop unusual sores or discharge, experience burning during urination, or have another potential exposure.

Don't wait for symptoms if you know you may have been exposed. Some infections are silent, and the best time to test depends on the infection and test used. A clinician can advise whether testing now and repeating it later is appropriate.

Seek prompt medical care if you have severe pelvic or testicular pain, fever with genital symptoms, or significant pain or swelling. If a possible HIV exposure occurred within the last 72 hours, seek urgent advice about PEP rather than waiting for symptoms. PEP is time-sensitive. The sooner you start, the better it works.

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If you're sexually active, getting tested isn't something to be ashamed of. It's something to be proud of. It means you're taking responsibility for your health and your partners' health. It means you're being an adult about it.

Don't rely on someone telling you they're clean. That word means nothing. People can be honest and still not know their status. Get tested. Ask your partners to get tested. Use condoms. Get vaccinated. And if you do test positive for something, don't panic. Most STIs are treatable or curable. The worst thing you can do is ignore it and let it get worse.

Talk to your doctor. Talk to your partners. And don't let shame stop you from taking care of yourself. Your health is worth more than your embarrassment.
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-GITMPLAYBOOK: Best Sex Toys for Vulva Owners: Beginner Buying Guide
-GITMPLAYBOOK: Penis Stimulation for Beginners: Guide to Solo Pleasure
GITMPLAYBOOK, GUIDE YOU THROUGH.

The Bottom Line

STIs are not proof that someone is dirty, unfaithful, or irresponsible. They are infections, and many are preventable, treatable, or curable.

The three habits that matter most are simple. Protect yourself. Get tested when appropriate. Get treatment when needed.

And remember that a clean-looking body, a trusted partner, or the absence of symptoms cannot confirm STI status. Knowing your status is far more useful than guessing. Your health is in your hands. Take care of it.

Disclaimer: This article is for educational purposes only and does not constitute medical advice. If you are experiencing symptoms of an STI, have had a potential exposure, or have concerns about your sexual health, please consult a qualified healthcare provider or sexual health clinic.

References

World Health Organization (WHO). Sexually Transmitted Infections: Fact Sheet.
Centers for Disease Control and Prevention (CDC). Chlamydia: Prevention and Testing.
Centers for Disease Control and Prevention (CDC). Gonorrhea: Prevention and Treatment.
Centers for Disease Control and Prevention (CDC). Syphilis: Prevention and Treatment.
Centers for Disease Control and Prevention (CDC). Genital Herpes: Prevention and Management.
Centers for Disease Control and Prevention (CDC). Genital HPV: Prevention and Vaccination.
Centers for Disease Control and Prevention (CDC). Trichomoniasis: Prevention and Treatment.
Centers for Disease Control and Prevention (CDC). HIV Prevention and Treatment.
Centers for Disease Control and Prevention (CDC). PEP and HIV Risk Reduction.
Centers for Disease Control and Prevention (CDC). Hepatitis B Prevention and Vaccination.
Centers for Disease Control and Prevention (CDC). STI Prevention and Testing Guidelines.