It’s likely to get an STD when you’re having sexual contact. One in two people who are engaging in sexual activity contract a sexually transmitted infection by the age of 25. But let’s get into the details of your risk from just one time of having unprotected sexual contact.

You won’t always know if someone has an STD, so you won’t necessary know when you’re at risk from an infected person. The person may not even know they have an STD, especially if they don’t experience symptoms, which is common.

Yet you probably know that simply having a sexual encounter puts you at risk of an STD. Is this risk really such a big deal or just fear-mongering? Let’s talk about the likelihood you could get some kind of STD from just one unprotected sexual act.

Chances of Getting an STD from a One Night Stand: What are the Odds?

This section will break down the odds of getting an STD in general, as well as your risk of some specific types of STDs.

Chances of Getting an STD from One Unprotected Encounter

It’s understandable to wonder about the odds of getting an STD, including from a one night stand or other unprotected encounter. You might wonder whether it’s really such a big deal to have unprotected sexual contact. Of course, this is probably more of a concern for you if you recently had an unprotected encounter and are now unsure of whether you could have been exposed to an STD. Even if the person you were with didn’t say anything about having an STD, it’s reasonable to wonder about the odds of catching an STD from that one encounter you had.

While it won’t necessarily happen, it only takes one time coming in contact with an infected person to acquire a sexually transmitted disease. STDs can be spread from person to person through body fluids and/or skin contact, depending on the type. Because of this, the odds of catching an STD are high from just one time. You only need to come in contact with that infection to get it. The risk goes up from unprotected sex with multiple partners, but it’s still there from one partner and one encounter.

Even from having unprotected sexual intercourse one time, you have about a 30 percent chance of getting gonorrhea, chlamydia or syphilis from someone who’s infected. So you can see that the chances of STD from one encounter are not 100 percent but that there are pretty good odds of getting one from just one time without protection.

You reduce the odds of getting an STD by using protection such as condoms, but you still don’t take away the risk completely. Condoms are very effective at reducing the odds of getting the types of STDs that spread through body fluids, such as gonorrhea or chlamydia. They are not as effective at reducing the risk of STDs that spread through skin contact, including HPV, syphilis or herpes. For condoms to be effective, you need to use them correctly, use them every time and use latex or polyurethane condoms without oil-based lubricants that could reduce their integrity.

Odds of Getting Herpes from One Encounter

Although herpes can have noticeable symptoms, you won’t necessarily know the person you’re with has herpes. It’s actually likely to get it without seeing symptoms. That’s because approximately 70 percent of the times herpes is spread it happens when the person is going through an asymptomatic period when symptoms are not present.

What are the chances of getting herpes from one unprotected encounter? The risk of getting herpes is about 10 percent for a woman catching it from a man or about four percent for a man getting it from a woman. Using condoms tends to reduce the risk of spreading herpes by about 30 percent. Condoms don’t help as much for herpes as they do for STDs that only pass through bodily fluids because you can get herpes through skin contact.

Probability of Getting HIV from One Encounter

You have much higher odds of getting HIV from a blood transfusion than from unprotected sex. Nonetheless, unprotected sex definitely comes with risk and can cause you to get HIV from just one time with an infected person. How likely is it to get HIV from one encounter? The odds of getting HIV from vaginal sex to the female are 1 in 1,250 in high-income countries and 1 in 333 in low-income countries. For men, it’s 1 in 2,500 in high-income countries and 1 in 263 in low-income countries.

You also have the chance of HIV infection from one encounter through anal sex. For this type of penetrative sex, there are certain factors that impact the risk. The risk is 1 in 70 for the receptive partner with ejaculation or 1 in 154 without ejaculation. For the insertive partner, the odds are 1 in 161 when uncircumcised or 1 in 909 when circumcised.

Chances of Getting Gonorrhea

You can also contract gonorrhea from one time of sexual activity. As mentioned above, the odds of getting gonorrhea from one unprotected encounter are about 30 percent.

Chances of Getting an STD from Oral

Various STDS are able to spread through oral sex just as they can through vaginal intercourse and through anal sex. There can be increased risk if you don’t use protection during oral sex, even if you do use them during other types of sex. Since pregnancy won’t happen by oral sex and people may find it more pleasurable without protection, it may be likely that you wouldn’t use protection during this type of sexual act. But the lack of protection makes you more vulnerable to contracting STDs.

It’s possible to get an STD of the mouth or throat from oral sex or to spread an STD from the mouth or throat to the genitals, rectum or anus, but it depends on the type of STD as to how it can spread and where in your body you can get it. You could also have an STD that shows itself both on the mouth/throat area and the genital area.

It’s hard to know whether your odds are higher with oral or penetrative sex. That’s because there haven’t been many studies on it and because people often have both types of sex, so it’s hard to separate them. It’s best to assume that you could get an STD from any type of sexual contact, which is true. When any type of sexual contact is unprotected, the risk is higher.

You have an STD oral sex risk from these STDs:

  • Herpes
  • HIV
  • Chlamydia
  • Gonorrhea
  • Human papillomavirus (HPV)
  • Trichomoniasis
  • Syphilis

It’s also possible to get hepatitis A from oral sex, and this infection is sometimes considered an STD because it can be spread through sexual contact as well as through other means.

Chances of STD from Oral

It’s not a cookie cutter response of your chances of contracting STD through oral sex. That’s because the answer varies by the type of STD you’re talking about and other factors that impact STD oral sex risk.

You reduce your chance of STD from oral if you use a condom or dental dam, or similar barrier method, when you have oral sex. Unprotected oral sex brings a risk of STD transmission every time, even just from one encounter.

Chances of Gonorrhea from Oral

Oral sex can cause the STD gonorrhea to spread from the genital, rectum and urinary tract area to the throat or vice versa. This is true for either males or females. So you have good chances of getting gonorrhea from oral sex.

Nonetheless, as you saw above, gonorrhea is not the only STD that can be passed through oral sex, so your probability of getting STD from oral is impacted by the many different STDs you could come in contact with. Chlamydia is similar in that it can spread from the throat to the genitals, rectum or urinary tract, and vice versa. HPV can also go from the throat to the genitals, anus or rectum and vice versa. HPV transmission can include the vagina and cervix.

Giving oral sex could give you syphilis, or you could give syphilis to someone if you have a syphilis infection on your lips, mouth or throat. It can impact the genitals, anus or rectum. Herpes can spread back and forth between the lips, mouth and throat to the genitals, anus, rectum or buttocks.

HIV can also spread through oral sex. The risk is lower of spreading HIV in this way than through other types of sex but it can still happen and repeated encounters without protection increase the risk. The odds to the receptive partner, such as giving oral sex to a man, are 0 to 1 in 2,500, while the odds for the insertive partner, such as a man getting oral sex, are close to zero.

Other Risk Factors?

Having unprotected sex is one of the risk factors that increases your chances of getting an STD from sexual activity. You also have greater risk if you try to use condoms but use them incorrectly or inconsistently. For example, maybe you use condoms every time but then skip them one time. That one time is enough to get an STD.

Some of the other factors that increase the likelihood of getting an STD include:

  • Engaging in sexual activity with numerous people; the risk goes up as the number of partners goes up
  • Being sexually assaulted
  • Currently having an STD or having one in the past, which makes you more vulnerable to catching another one
  • Being between 15 and 24, which are the ages with the highest STD rates
  • Using alcohol or drugs, which lowers inhibition

There’s a higher likelihood that you could spread STDs through oral sex if you have certain factors. These include genital or mouth sores, poor oral health or being exposed to pre-ejaculate or ejaculate of an infected person.

Factors Involved in the Chance of Contracting HIV from a Single Encounter

There are certain factors that greatly increase or decrease your one time unprotected encounter HIV risk. It’s significantly less likely for a man to get it when circumcised, and the risk is much lower with condoms, pre-exposure prophylaxis or treatment as prevention. On the other hand, you have a much higher risk during an HIV single encounter when there is an acute infection, about 12 weeks after first getting HIV, which makes the risk 26 times more likely.

Unprotected Sex STD Risk

There is a significant likelihood of STD transmission from a single time of unprotected sex. As you can see, protection also does not completely take away the chances of contracting STD from one encounter. Abstinence is the only way to prevent the transmission completely. Nonetheless, you have a higher risk when you don’t use protection, even just from one encounter.

It’s best to assume that you have chances of STD transmission every time you have sex. Take precautions to prevent the spread by using protection every time. Also, you can greatly reduce the risk if you only have sexual contact with one other person, with both of you having been tested with negative results.

The only way to know for sure if you’ve picked up an STD from an unprotected sexual encounter is to get tested. If the person you were with told you they have a specific STD such as herpes or gonorrhea, it makes sense to get tested for that. But since you’re not truly sure what STDs the person could have, you may want to do a complete STD test to be sure about your state of health. If you discover that you do have an STD, it’s nothing to be ashamed of. It’s simply something that could impact your health in a negative way, especially if it goes untreated. It’s important to find out if you have an STD so you can be treated.