How Are STDs Spread?

Medically reviewed by Rosanna Sutherby, PharmD on October 13, 2020. To give you technically accurate, evidence-based information, content published on the Everlywell blog is reviewed by credentialed professionals with expertise in medical and bioscience fields.

How are STDs spread and how do you get STDs? These are good questions to ask if you want to prioritize your sexual health: by knowing how STDs are spread, you can take more proactive steps toward prevention.

In this guide, you’ll discover how sexually transmitted infections spread, along with key information on symptoms, potential complications associated with untreated STDs, prevention tips, and more—so let’s get started.

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How STDs are spread

Sexual contact

Sexually transmitted infections are typically spread through sexual contact. They’re caused by bacteria, viruses, or parasites that spread from one person to another in semen, blood, or vaginal and bodily fluids. An STD can be passed through vaginal sex, anal sex, and oral sex. Note that ejaculation does not have to occur for an STI to be transmitted from one partner to another.

Nonsexual transmission

Some STDs can also be spread non-sexually through blood transfusions and shared needles. Unsterile body piercings or tattooing equipment can transmit some infections like HIV, hepatitis B, and hepatitis C.

Mother to baby

STD transmission can occur from a mother to the baby during pregnancy or childbirth. These infections include gonorrhea, chlamydia, HIV, and syphilis.

Skin-to-skin contact

Infections that can cause genital ulcers, including genital herpes, syphilis, and human papillomavirus (HPV), are often transmitted through skin-to-skin contact with an infected sore.

Three main causes of STDs

  • Bacteria: including chlamydia, gonorrhea, and syphilis
  • Viruses: including HIV, herpes simplex virus, human papillomavirus, hepatitis C virus, cytomegalovirus (CMV), and Zika
  • Parasites: such as Trichomonas vaginalis or insect-like organisms such as crab lice or scabies mites

How unprotected sex spreads STDs

Many people wonder, “Can you get an STD with a condom?” The answer is “yes.” Here we’ll discuss what condoms can protect against as well as their limits for certain infections.

Condom effectiveness

Condoms are 98% effective at protecting against most STDs like chlamydia and gonorrhea. When used consistently and correctly, condoms are highly effective at preventing HIV transmission, which is the virus that causes AIDS.

The latex condom reduces the risk of other sexually transmitted infections as well, such as those transmitted by genital secretions.

Condoms can also help to protect against infections associated with genital ulcers. They may reduce the risk for human papillomavirus (HPV) infection along with the conditions linked to HPV, such as genital warts and cervical cancer.

What condoms don’t always protect against

Some people are surprised to hear that condoms do not always protect against all STDs. This raises the question: how do you get STDs if you use condoms? The answer is that some STDs can spread through skin-to-skin contact. In the case of genital herpes or syphilis, for example, you can contract or spread the infection even when you’re wearing a condom. This is because a condom may not cover all areas of the skin that can be exposed to or transmit the infection.

That being said, consistent condom usage does greatly reduce the risk of getting or transmitting infections like genital herpes or syphilis—so, in general, it’s a good idea to consistently use protection when having sex.

Symptoms of STDs

When learning how STDs are spread, it can help to know the symptoms associated with sexually transmitted infections. These symptoms can appear a few days after exposure to the infection, or—in some cases—it can take years before they show up.

Here are some STD symptoms to be aware of:

  • Sores or bumps in the mouth, rectal area, or on the genitals
  • Pain or burning during urination
  • Penile discharge
  • Vaginal discharge that is unusual or odd-smelling
  • Unusual vaginal bleeding
  • Experiencing pain during sexual intercourse
  • Sore, swollen lymph nodes (particularly in the groin)
  • Pain in the lower abdomen
  • Fever
  • A rash over the trunk of your body, your hands, or your feet

Sexually transmitted diseases (STDs) or sexually transmitted infections (STIs) don’t always lead to noticeable symptoms. In some cases, people may have an infection and not even be aware of it (all the more reason why learning how often to get tested for STDs is a great way to take charge of your sexual health). In some cases, an STD may go undiagnosed until health complications develop or a partner receives a diagnosis.

Left untreated, some STDs—including chlamydia, gonorrhea, HIV, and HPV—can result in serious health complications, including:

  • Pelvic inflammatory disease (PID)
  • Complications during pregnancy and delivery
  • Inflammation of the eyes
  • Arthritis
  • Infertility
  • Heart disease
  • Certain cancers, like HPV-associated cervical cancer and rectal cancers

STD prevention

The only way to avoid STD transmission is to not have sex with someone who is infected. Because it can be difficult to know if a person is infected (especially if they show no symptoms and haven’t been tested recently), adopting the following safe sex practices can help reduce your risk of getting infected:

  • Use a condom consistently when you have sex—and make sure it’s used correctly
  • Have a sexual relationship with only one long-term, mutually monogamous partner who has been tested and has no infections
  • Limit your number of sexual partners, and/or be sure to frequently test for STDs (talk with your healthcare provider to learn what testing schedule they recommend for you—and be sure you’re open about the number of sex partners you have)

Talking about STDs with your partner(s)

Now that you know how you could get STDs, work toward having open and honest conversations about STDs and sexual health with your partner(s). It can be uncomfortable to talk about STDs with a new partner, but remember that wanting to prevent STDs is nothing to be ashamed of. It’s your body and your sexual health, after all. (Related content: How to ask your partner to get tested for STDs)

Here are some questions to consider discussing with your sex partner as you look toward having safe sex and preventing the spread of STDs:

  • How many partners have you had?
  • Do you currently have other partners besides me?
  • Do you know if you have any STDs currently?
  • When was the last time you were tested for STDs?
  • Have you ever been treated for an STD?
  • How many sex partners have you had since your last test?
  • Have you ever been tested for HIV?
  • Have you ever injected drugs?
  • How often do you use protection?
  • Do you always use protection when you’re with a new sexual partner?
  • What kind of protection do you use?
  • If you use condoms, what kind of condoms do you use?

We know that pulling out a list of questions is the least romantic thing to do when you’re in-the-moment. So, if you’re thinking about being sexually active with a new partner, set up a time to talk before you have sex. Try to navigate the conversation with reassuring phrases like “Let’s talk about how we can protect each other” or “Let’s get tested together.”

STD diagnosis

STDs are typically diagnosed by a healthcare professional. They will usually ask questions about your sexual history. They may take a sample of fluid from your vagina or penis, or run a blood test. Certain laboratory tests can show which bacterial or viral STDs you may have.

STD statistics

Relevant to the discussion of how STDs are spread are some key statistics related to the transmission and prevalence of various sexually transmitted infections. According to the World Health Organization:

  • More than 1 million sexually transmitted infections are contracted daily around the globe
  • Each year, there are approximately 376 million new infections of chlamydia, gonorrhea, syphilis, or trichomoniasis
  • An estimated 500 million people have genital herpes
  • Human papillomavirus (HPV) is the most common STD, and over 290 million women have an infection
  • With the majority of STD cases, individuals don’t have any symptoms or have very discreet symptoms
  • Certain STDs, including herpes type 2 and syphilis, can put an individual at increased risk of acquiring HIV
  • 988,000 pregnant women were infected with syphilis in 2016, which resulted in more than 350,000 adverse birth outcomes

Testing for STDs at home

Testing for STDs is one of the most important steps you can take to protect your sexual health, and—fortunately—STD testing can be easy and straightforward: our at-home STD Test for men and STD Test for women lets you check for 6 sexually transmitted infections from the convenience of home. Plus, if positive results are detected, you’ll have the option to connect with our independent physician network (at no extra cost) to talk through your results and potentially receive a prescription for medication, if appropriate.


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3. Tattoos: Understand risks and precautions. Mayo Clinic. URL. Accessed November 13, 2020.

4. Fact Sheet for Public Health Personnel. Centers for Disease Control and Prevention. URL. Accessed November 13, 2020.

5. What are Sexually Transmitted Infections (STIs) or Diseases (STDs)? Urology Care. URL. Accessed November 13, 2020.

6. Sexually transmitted infections (STIs). WHO. URL. Accessed November 13, 2020.

7. Genital HPV Infection - Fact Sheet. Centers for Disease Control and Prevention. URL. Accessed November 13, 2020.

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