Sex Myths: STDs Are Transmitted Every Time You Have Sex

A lot of sex myths revolve around how to tell whether you have a cheating partner. One particularly poisonous idea is the myth that if your long-term partner is suddenly diagnosed with a new sexually transmitted disease (STD) infection, it must mean they're cheating.

After all, if you were the source of the STD, your partner would have been infected a long time ago. Right?

Wrong! There is a simple, incorrect assumption lurking behind this sex myth. That assumption is that if you have an STD, it will be transmitted every time you have sex. But that isn't actually true.

In fact, there are a number of factors that can affect the likelihood of any particular STD being spread. The risk can be quite different depending on the circumstances surrounding any encounter where you are having sex.

STDs aren't transmitted every time you have sex, but they can be transmitted any time you have sex.

You can get an STD the first time you have sex. But there are no STDs that will always be transmitted every time someone has sex.

Also, a new STD diagnosis doesn't mean that the person recently got the STD or was cheating in the current relationship: There can be asymptomatic shedding of a virus or an active infection with no signs, which can lead to STD transmission without someone being aware.

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Factors Affecting STD Transmission

A number of factors might affect whether you'll pass on an infection during a sexual encounter. These include:

  • The type of infection
  • The amount of virus/bacteria in your blood or in your genital secretions (the severity of your infection)
  • Whether you or your partner have any open sores or other wounds on your genitals, or whether you have broken skin in other areas where you'll have skin-to-skin contact during sex
  • The presence of other STDs in either you or your partner, as other STDs can increase the risk of spreading an infection or getting an infection 
  • How much time you spend having sex
  • Whether you have safe sex, and whether you have it correctly 
  • Whether you use sexual lubricants
  • The type of lubricants you use
  • The gender of the infected partner
  • The gender of the uninfected partner
  • The types of sex you are having (e.g. anal, vaginal, oral)
  • The overall health of you and your partner, especially regarding your immune system
  • Whether you have an infection at the time of exposure to another STD

Uncertain Timing of STD Transmission

Just because your partner has only recently been diagnosed with an STD when the two of you have been together for a long time, it does not necessarily mean that they have been cheating on you.

In such a circumstance, there are actually several possible alternate explanations. These can be difficult to choose between. That's particularly true if you weren't both screened for STDs before getting into the relationship.

For example, many STDs can have no symptoms in you or your partner, even if most cases do come with symptoms. Imagine if you turn out to be asymptomatically infected with the same STD but weren't screened before getting together. In that case, there is a possibility that you were infected the whole time.

Other possibilities include:

  • You may have only recently transmitted the disease to your partner.
  • Your partner may only have recently developed symptoms.
  • You both could have been infected since before your relationship started.
  • You may simply not have recognized the symptoms until just now.
  • Your partner may not have symptoms but switched to a doctor who does routine testing.

Protecting Your Sexual Health

STDs aren't necessarily transmitted every time you have sex. However, that doesn't mean you can assume they won't be transmitted during any particular time you are having sex. An STD can be transmitted the first time you have sex with someone or it may not be transmitted until the 50th.

Is your health something you want to trust to luck? Probably not. Therefore, it's your responsibility to minimize your risk. Ensuring that testing is done for both partners at the beginning of the relationship is always helpful.

Practicing safe sex is a lot more reliable than relying on probability or prayer. That's particularly true when safe sex is combined with appropriate testing.

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Article Sources
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  1. Koelle DM, Wald A. Herpes simplex virus: the importance of asymptomatic sheddingJ Antimicrob Chemother. 2000;45 Suppl T3:1‐8. doi:10.1093/jac/45.suppl_4.1

  2. Dembo R, Belenko S, Childs K, Wareham J, Schmeidler J. Individual and community risk factors and sexually transmitted diseases among arrested youths: a two level analysisJ Behav Med. 2009;32(4):303‐316. doi:10.1007/s10865-009-9205-8

  3. Centers for Disease Control and Prevention. STDs and HIV – CDC fact sheet. Updated October 8, 2019.

  4. Gorbach PM, Weiss RE, Fuchs E, et al. The slippery slope: Lubricant use and rectal sexually transmitted infections: A newly identified risk. Sex Trasm Dis. 2012;39(1):59-64. doi:10.1097/OLQ.0b013e318235502b

  5. Johnson LF, Alkema L, Dorrington RE. A Bayesian approach to uncertainty analysis of sexually transmitted infection modelsSex Transm Infect. 2010;86(3):169‐174. doi:10.1136/sti.2009.037341

  6. Lee KC, Ngo-Metzger Q, Wolff T, et al. Sexually transmitted infections: Recommendations from the U.S. Preventive Services Task Force. Am Fam Physician. 2016;94(11):907-915.

  7. Morales A, Espada JP, Orgilés M, Escribano S, Johnson BT, Lightfoot M. Interventions to reduce risk for sexually transmitted infections in adolescents: A meta-analysis of trials, 2008-2016PLoS One. 2018;13(6):e0199421. Published 2018 Jun 28. doi:10.1371/journal.pone.0199421

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