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Queensland Health

Sexually transmissible infections (STI's)

Sexually transmissible infections (STIs) are infections that can be passed on from one person to another during sex. The most common STIs in Australia are genital herpes, genital warts, chlamydia, trichomoniasis, gonorrhoea, hepatitis B, syphilis, and HIV.

Find out more about these and other STIs

How do you get an STI?

If you have had unprotected sex, you may be at risk of an STI.

STIs can be passed from person to person through:

  • vaginal, oral and anal sex
  • close skin-to-skin sexual contact (eg. foreplay, touching the genitals, mutual masturbation)
  • direct blood-to-blood contact
  • pregnancy or childbirth (from mother to child)
  • sharing injecting drug equipment.

Using condoms reduces the spread of many STIs (including HIV) but some STIs can spread from person to person even when condoms are used. For example, if your partner has genital herpes or warts, the condom may not cover the lesions or sores on his/her genitals and you may be at risk.


Many STIs have no obvious symptoms, so a person can often have an STI without knowing it. A person with an STI may look and feel perfectly healthy.

While some infections appear to go away without treatment, they actually stay active in the body (eg. in the bloodstream or lining of your throat, cervix or anus). This means that you can pass an STI onto other sexual partners and even your baby without knowing that you are infected.

Girls may notice:

  • itching, sores, blisters or lumps inside and/or around the vagina or anus
  • pain low in the tummy
  • pain during sex
  • unusually heavy periods, bleeding between periods, or bleeding after sex
  • unusual vaginal discharge
  • pain/burning when passing urine and/or frequent urge to pass urine
  • rectal pain/discharge.

Guys may notice:

  • discharge from the penis
  • sores, blisters or lumps on the penis, pubic area or around the anus
  • pain/burning while passing urine and/or frequent urge to pass urine
  • pain in the scrotum
  • rectal pain/discharge.

These symptoms have many causes and do not necessarily mean you have an STI. However, many STIs have no obvious symptoms! If you think you have put yourself at risk then see your local doctor, family planning or sexual health clinic.

What to do

If you have had unprotected sex or are concerned you have an STI, it is best to talk it over with your local doctor, family planning clinic or sexual health clinic as soon as possible.

More info