Viral vs. Bacterial STDs: What's the Difference?

Bacterial STDs are caused by bacteria — microscopic, single-celled organisms. When bacteria infect the body, they can affect specific areas (like the reproductive tract, throat, or rectum).

The good news: the body doesn't hold onto bacteria permanently. With the right antibiotic treatment, common bacterial STIs such as chlamydia, gonorrhea, and syphilis can be cured.^[1]

One major risk with bacterial STDs is not knowing you have one. Many cause few or no symptoms, which means many people may not know they're infected. Left untreated, infections such as chlamydia, gonorrhea, and syphilis can lead to serious complications even without noticeable symptoms.^[3]

Common Bacterial STDs

Chlamydia

Chlamydia is the most frequently reported STD in the United States.^[4] It's caused by the bacterium Chlamydia trachomatis and often causes no symptoms at all. When symptoms do occur, they may include unusual discharge, burning during urination, or pelvic pain. Untreated chlamydia can spread to the uterus and fallopian tubes, potentially causing pelvic inflammatory disease (PID) and long-term fertility problems. It can be cured with prescription antibiotics. Doxycycline is commonly used, while other regimens may be recommended in certain situations, including pregnancy.^[4]

Gonorrhea

Gonorrhea is caused by Neisseria gonorrhoeae and can infect the genitals, rectum, and throat. Like chlamydia, it's frequently asymptomatic — particularly in women. When symptoms appear, they may include burning when urinating, white, yellow, or green discharge, or rectal discomfort. Untreated gonorrhea can cause PID and epididymitis, and it can increase the chance of acquiring or transmitting HIV.^[5] Treatment typically includes a ceftriaxone injection. If chlamydia has not been ruled out, a clinician may also recommend treatment for chlamydia.^[6]

Syphilis

Syphilis is caused by the bacterium Treponema pallidum and progresses through distinct stages if untreated. The first sign is usually a painless sore (chancre) at the infection site. Without treatment, syphilis advances to a secondary stage (rash, flu-like symptoms), then a latent period with no symptoms, and finally a tertiary stage that can cause severe damage to the heart, brain, and other organs. Early-stage syphilis is easily cured with a penicillin injection; later stages require more intensive treatment.^[7]

Trichomoniasis

Trichomoniasis (trich) is caused by a microscopic protozoan parasite — Trichomonas vaginalis — not technically a bacterium, but it behaves similarly in that it's curable with antibiotics.^[8] It is one of the most common curable STIs in the United States. CDC estimated that more than 2 million people had trichomoniasis in 2018.^[8] Most people with trich have no symptoms, but when symptoms appear, they can include genital itching or irritation, discomfort when urinating, and changes in discharge.^[8] Trich is treated with prescription oral medication, and current partners should be treated at the same time to help prevent reinfection.^[9]

Viral STDs are caused by viruses — microscopic infectious agents that reproduce inside the body's cells.. Their long-term course varies by infection: most HPV infections clear on their own, hepatitis C can be cured, and HIV, HSV, and chronic hepatitis B can be managed but are not currently cured.^{[2, 10, 11, 12, 13]}

That said, "incurable" doesn't mean "unmanageable." Treatment depends on the infection: antiretroviral therapy can control HIV, antiviral medications can reduce genital herpes outbreaks, and medication can help manage chronic hepatitis B. Vaccines can help prevent new HPV and hepatitis B infections, but they do not treat an infection that is already present.^{[11, 12, 13, 14, 15]}

Common Viral STDs

Human Papillomavirus (HPV)

HPV is a very common STD in the United States. Nearly every unvaccinated person who is sexually active will get HPV at some point in their life.^[10] Most HPV infections clear on their own within 1–2 years without causing any problems. But some high-risk strains can cause cervical cancer, as well as cancers of the throat, anus, vagina, vulva, and penis. Other strains cause genital warts.^[10]

There's no treatment for the virus itself, but related health problems can be managed. Genital warts can be treated, and recommended cervical cancer screening can help find cell changes that may need follow-up or treatment.^[10] The HPV vaccine is recommended for everyone through age 26 if they have not been adequately vaccinated. Some adults ages 27 to 45 may decide to get vaccinated after discussing it with a clinician. The vaccine prevents new HPV infections but does not treat an infection that is already present.^[11]

Herpes Simplex Virus (HSV)

There are two types: HSV-1, which primarily causes oral herpes (cold sores), and HSV-2, which primarily causes genital herpes — though either type can infect either location.^[12] After infection, HSV remains in the body and can reactivate later, causing outbreaks of sores or blisters.^[12]

Many people with herpes never have noticeable symptoms, or mistake them for something else. For people with recurrent genital HSV-2, daily antiviral medication can reduce outbreak frequency. Daily valacyclovir can also lower, but not eliminate, the risk of passing HSV-2 to a partner.^[12]

HIV (Human Immunodeficiency Virus)

HIV attacks the immune system by destroying CD4 T-cells, the cells that help the body fight infection. Without treatment, HIV can progress to AIDS (Acquired Immunodeficiency Syndrome), at which point the immune system is severely compromised. Early HIV can cause flu-like symptoms that can be mistaken for other illnesses, followed by a long asymptomatic period during which the virus continues to replicate.^[14]

While there's no cure for HIV, antiretroviral therapy (ART) is highly effective. People on ART can reach an "undetectable" viral load — meaning the virus is suppressed to levels so low it cannot be transmitted to partners (U=U: Undetectable = Untransmittable).^[15] With consistent treatment, people with HIV can expect a near-normal lifespan.^[16]

Hepatitis B

Hepatitis B is a viral infection that attacks the liver. It's spread through sexual contact, shared needles, and from mother to baby at birth. Most adults clear acute hepatitis B infection on their own, while fewer than 5% develop chronic hepatitis B. Chronic infection can lead to cirrhosis and liver cancer over time.^[13] A highly effective vaccine prevents hepatitis B entirely, and antiviral medications are available to manage chronic infection.^[13]

Hepatitis C

Hepatitis C is primarily a bloodborne infection, although it can be transmitted through sex. Direct-acting antiviral medications can cure more than 95% of people with hepatitis C, usually within 8 to 12 weeks. It is most often spread through contact with infected blood, commonly by sharing injection equipment. Sexual transmission is uncommon, but risk can be higher for people with HIV, other STIs, multiple sexual partners, or anal sex. Hepatitis C often causes no symptoms, and chronic infection can quietly damage the liver over time.^{[2, 17]}

The most clinically important distinction between bacterial and viral STDs comes down to curability:

• Bacterial STDs such as chlamydia, gonorrhea, and syphilis can be cured with the right antibiotic treatment. Treatment clears the infection, though it may not reverse complications that have already developed. You can still get reinfected after treatment because it does not provide immunity.^[1]
• Viral STDs do not all behave the same way. HIV, HSV, and chronic hepatitis B can be managed but are not currently cured. Many HPV infections clear on their own, while hepatitis C can be cured with direct-acting antiviral medication.^[1,2,10]

Neither category is automatically more serious. Both bacterial and viral STIs can cause serious complications when they are not diagnosed and treated or managed. Early testing and appropriate care can help prevent complications and reduce transmission.^[1,7]

Testing methods vary depending on the infection:

Because many STDs — both bacterial and viral — have no obvious symptoms, routine testing is a reliable way to know your status. The CDC recommends that all sexually active women under 25 get tested for chlamydia and gonorrhea every year, and that all adults between 13 and 64be tested for HIV at least once. If you have new or multiple partners, more frequent testing is recommended.^[18]

Both bacterial and viral STDs carry serious risks when left untreated. Some of the most significant complications:

• Pelvic inflammatory disease (PID): Untreated chlamydia or gonorrhea can spread to the uterus and fallopian tubes, causing PID — a major cause of infertility, chronic pelvic pain, and ectopic pregnancy.^[4,6]
• Infertility: Chlamydia and gonorrhea can affect fertility. In women, they can lead to PID; in men, they can cause epididymitis, which may affect fertility.^[4,6]
• Cancer: HPV causes the majority of cervical cancers, as well as cancers of the throat, anus, vagina, vulva, and penis. Chronic hepatitis B and C can lead to liver cancer.^[2,10,13]
• Increased HIV risk: Having an active STD — especially one that causes sores (like herpes or syphilis) — increases both the risk of contracting HIV and transmitting it.^[1,12]
• Pregnancy complications: SomeSTDs can be passed from mother to baby during pregnancy or childbirth, causing stillbirth, low birth weight, eye infections, pneumonia, and neonatal herpes.^[1,12]
• Neurological and organ damage: Chronic hepatitis B or hepatitis C can lead to cirrhosis, liver cancer, and liver failure over time.^[2,7,13,14]

• Use condoms consistently. Condoms reduce the risk of many bacterial and viral STDs including fluid-transmitted infections (HIV, chlamydia, gonorrhea) but do not eliminate risk.. They offer less protection against infections such as HPV and herpes when infected skin is outside the area covered by the condom.^[19]
• Get vaccinated. Vaccines are available for HPV and hepatitis B — two viral STDs that can cause cancer. If you haven't been vaccinated, talk with a healthcare provider about whether vaccination is recommended for you.^[11,13]
• Get tested regularly. Because many STDs cause no symptoms, routine testing is a reliable way to know your status and catch infections before they cause complications.^[18]
• Discuss status with partners. Knowing your own status — and your partner's — allows you to make informed decisions about protection.
• Consider PrEP if you may beat risk for HIV. Pre-exposure prophylaxis (PrEP) is a medicine that is highly effective at preventing HIV infection in people who are HIV-negative.^[20]
• Limit the number of sexual partners. Fewer partners means fewer opportunities for exposure — for both bacterial and viral infections.^[19]

Whether you're concerned about a bacterial or viral STD, testing is always the right first move. Most STDs have no symptoms — meaning the only way to know your status is to test.

Everlywell's at-home STD test screens for the most common bacterial and viral STDs — including chlamydia, gonorrhea, trichomoniasis, HIV, syphilis, and hepatitis C — all from a single at-home collection. Mail your sample to a certified lab and get secure, confidential results online within days. No waiting room required.

If you have symptoms or received a positive result and need to talk to a provider, Everlywell also offers online STI treatment consultations in 2 hours or less. A licensed provider can evaluate your situation and send a prescription to your pharmacy if appropriate.

Taking care of your sexual health is one of the most important things you can do. Everlywell makes it easy to do it on your own terms.