An STD (sexually transmitted disease), also referred to as an STI (sexually transmitted infection), occurs when a virus, bacteria, or parasite is transmitted through sexual contact. STIs denote the infection stage, while STDs refer to the resulting disease. Though the terms are often used interchangeably, it’s helpful to distinguish between them. Today, STDs are extremely common, with approximately 20 million new cases each year, especially among adolescents, young adults, and men who have sex with men.

Viral STDs

Human Papillomavirus (HPV) is the most common STD in the U.S. Many infected people experience no symptoms, but some strains cause genital warts or increase cancer risk. Screening through Pap or HPV tests is essential, and prevention is available via vaccination.

Human Immunodeficiency Virus (HIV) attacks the immune system and, if untreated, progresses to AIDS. Modern antiretroviral therapy (ART) keeps the viral load low, enabling people with HIV to live healthy lives.

Genital Herpes (HSV‑1 and HSV‑2) can cause painful cold sores or blisters on the genitals or mouth, though many show no symptoms. There is no cure, but antiviral medications reduce outbreaks.

Viral Hepatitis (A, B, C) can be sexually transmitted. All forms inflame the liver; some are preventable by vaccines, and most are treatable with antiviral medications.

Zika Virus is primarily mosquito-borne, but can be sexually transmitted. It causes fever and joint pain, and can lead to birth defects. Prevention includes avoiding travel to outbreak zones and using protection during sex.

Bacterial STDs

Chlamydia (Chlamydia trachomatis) often shows no symptoms but can cause discharge, pain, and fever. Left untreated, it may lead to pelvic inflammatory disease (PID). Antibiotics effectively cure it.

Gonorrhea (Neisseria gonorrhoeae) causes painful urination and discharge. It may also infect the throat or rectum, leading to PID. Treated with antibiotics, but resistance is a growing concern.

Syphilis (Treponema pallidum) begins with a painless sore (chancre) but can progress to systemic disease including neurological, cardiac, or congenital complications. Penicillin remains the standard treatment.

Trichomoniasis (Trichomonas vaginalis) is a parasitic infection that causes irritation, odor, and discharge. It’s linked to preterm birth and low birth weight. Easily treated with antibiotics.

Mycoplasma genitalium (Mgen) causes similar symptoms to chlamydia and gonorrhea. Untreated, it can lead to urethritis or pelvic infection. Treated with specific antibiotics.

Pelvic Inflammatory Disease (PID) isn’t an STD itself, but is often caused by untreated chlamydia or gonorrhea. It results in pelvic pain, fever, and serious consequences such as infertility and abscesses.

Lymphogranuloma Venereum (LGV) is caused by certain chlamydia strains. It leads to genital swelling, ulcers, and enlarged lymph nodes. Treated with antibiotics.

Chancroid (Haemophilus ducreyi) is rare in developed countries. It causes painful genital ulcers and lymph node swelling, which increases HIV risk. Antibiotics are effective.

Bacterial Vaginosis (BV) isn’t always sexually transmitted, but is linked to sexual activity. An overgrowth of vaginal bacteria causes odor and discharge; untreated BV increases PID and preterm birth risks.

Parasitic STDs

Pubic Lice (“Crabs”) are tiny insects that cause intense itching. They cling to pubic hair and lay eggs (nits). Treatment involves lice-killing lotions and washing bedding and clothing thoroughly.

How STDs Are Detected

Most STDs are diagnosed through testing. Common methods include:

  • Urine tests or swabs for chlamydia, gonorrhea, trichomoniasis, and M. genitalium.

  • Blood tests for HIV, syphilis, and viral hepatitis.

  • Visual inspection for genital warts or chancroid.

  • Microscopic exam for trichomonas and pubic lice.

It’s important to get tested regularly if you’re sexually active, especially with new or multiple partners. Many STDs show no symptoms, meaning you may not know you have one.

Symptoms of STDs

Symptoms vary by infection:

  • Discharge from genitals or anus

  • Burning during urination

  • Genital sores, warts, or ulcers

  • Itching or irritation

  • Rash (e.g., secondary syphilis)

  • Fever, fatigue, headache, achiness (common with HIV or viral hepatitis)

Some infections, like HIV or chlamydia, can be asymptomatic for years—making testing and early detection critical.

Potential Complications

If left untreated, STDs may lead to serious health problems:

  • Infertility (e.g., from PID, HIV, or syphilis)

  • Cancer (from HPV or prolonged hepatitis B/C)

  • Birth defects (from congenital syphilis, Zika, or untreated STDs during pregnancy)

  • Increased HIV transmission risk due to sores or ulcers

  • Chronic illness (e.g., HIV, hepatitis)

  • Social, emotional, or financial stress

Treatment Options

  • Antibiotics cure bacterial and parasitic STDs (e.g., chlamydia, gonorrhea, syphilis, trichomoniasis, LGV, chancroid, BV, pubic lice).

  • Antivirals manage viral infections (e.g., HIV, herpes, hepatitis). HIV treatment includes lifelong antiretroviral therapy; herpes outbreaks are reduced with antivirals.

  • Supportive care (rest, hydration) for mild viral infections like Zika, when no specific treatment exists.

Timely treatment not only resolves infection but also prevents complications and reduces transmission.

Prevention Strategies

  • Use condoms or dental dams consistently and correctly.

  • Limit sexual partners and prioritize mutual monogamy.

  • Routine testing for both you and your partners.

  • Vaccinations: HPV and hepatitis A/B.

  • Avoid sharing needles or intimate items that can transmit infection.

  • Abortive treatment reduces transmission risk, as does immediate therapy following diagnosis.

Living with an STD

Having an STD can be alarming, but most are treatable or manageable. People with HIV, for example, can have long, healthy lives with treatment. Managing ongoing conditions like herpes involves medications and lifestyle adjustments.

Getting an STD diagnosis doesn’t define you—it’s an opportunity to protect your health and foster better awareness and communication with partners.

Conclusion

STDs encompass a wide range of sexually transmitted infections—from viruses like HPV and HIV to treatable bacterial and parasitic infections. Early detection through regular testing, safe sexual practices, and prompt treatment are essential. Education and communication help prevent spread, protect your health, and reduce complications. If you suspect you have an STD or have a new partner, speak with a healthcare provider for evaluation and care.