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Sexually transmitted diseases (STDs)

By Glenna C. Bailey

An STD passes from one person to another during sexual activity. This activity may include intercourse, oral sex, anal sex or sex play. 

STD is an older term. Sexually transmitted infection (STI) is the more common term today. This is because a person may have no symptoms, but they still have an infection that needs treatment.

What causes STIs?

The main causes of STIs are:

  • Bacteria: For example, chlamydia, gonorrhea and syphilis are caused by bacteria.
  • Viruses: For example, HIV and AIDS, herpes, “genital warts” (human papillomavirus, or HPV), viral hepatitis and Zika are caused by viruses. 
  • Parasites: For example, “trich” (trichomonas vaginalis) is caused by a parasite. 
  • Insects: For example, crab lice and scabies mites are caused by insects. 

How do STIs spread?

STIs can spread from one person to another through sexual contact with the:

  • Penis
  • Vagina
  • Mouth
  • Anus
  • Membranes lining the urinary or genital tract

Some infections can spread through close, nonsexual contact with skin. 

Who’s at risk for STIs?

Anyone who has sex can get an STI. Your risk goes up if:

  • You have more than one partner
  • Your partner has other partners
  • You or your partners have had sex with other people in the past 
  • You have an STI that increases your risk for new infections 

How can I prevent STIs?

You can help prevent STIs. Just start with these steps:

Talk with your partner

Protect yourself and your partner by talking about sex beforehand. This might feel awkward, but your health is worth it.

Use condoms

Use a condom every time. And use condoms the right way.

Have fewer partners

Agree with your partner to have sex only with each other. Get tested to be sure you’re both free of STIs. And if you have an STI, get treatment before having sex.

Get vaccines

HPV is the most common STI. You can help prevent HPV with a safe, effective vaccine. Children can get the vaccine at age 11 or 12 to help protect their long-term health. Catch-up vaccination is now recommended for those up to 26 years of age. 

Your doctor may also advise you to get the hepatitis A and B combination vaccine. These diseases can spread through sexual or close contact.

Abstain from sex

The best way to prevent STIs is to not have sex.

How do I know if I have an STI?

The only way to know for sure is to see your doctor. Watch for changes in your body and your partner’s body. People can have symptoms in or near the vagina, penis, rectum, mouth or throat. Some signs may include:

  • Unusual discharge
  • Lumps, bumps or rashes
  • Painful, itchy or painless sores
  • Itchy skin
  • Burning when you pee
  • Pain in the pelvis, abdomen or anus
  • Bleeding from the anus

Keep in mind that STIs don’t always have symptoms. If you do have an STI, be sure you and your partner both get treatment.

Protect your long-term health

Changes in your body can be scary. But don’t ignore them or put off seeing your doctor. Left untreated, some STIs can lead to serious problems, like:

  • Cancer
  • Sterility (not being able to have children)
  • Harm to unborn babies whose mothers are infected

What if I test positive?

Testing positive means you have an STI. Remember, all STIs are treatable, and many are curable. You’ll want to see your doctor. Both you and your partner should get treatment right away.


About the author

Glenna C. Bailey is a health literacy champion, fan of the Apostrophe Protection Society and staunch supporter of the serial comma. She loves writing about consumer health and making info easier to find, understand and act on.

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