Also called

  • STI, STD, sexually transmitted infection, sexually transmitted disease


  • Anyone who is sexually active can catch an STI.
  • Correct use of condoms and dams can help reduce the risk of catching an STI.
  • Not all STIs show symptoms, so it is important to have an STI check if you have changed sexual partners.
  • Medical treatment can cure some STIs or help relieve symptoms for others.
  • If you have been diagnosed with an STI, let your sexual partners know and encourage them to attend a clinic for testing and treatment.

Sexually transmissible transmitted infections (STIs, previously known as sexually transmitted infections) are common all around the world. They may be caused by bacteria, viruses or parasites. You may think that only other people get STIs and that you are not at risk of catching one, but anybody who is sexually active can get an STI if they do not practice safe sex. STI can also be passed from mother to child during pregnancy and at birth.

You can’t tell just by looking at a person that they have an STI. If you have unprotected sex with a person who has an STI, you are at high risk of catching that infection.

Sexually transmissible infections include, among others, chlamydia, herpes, gonorrhoea, syphilis, Mycoplasma genitalium, genital herpes, scabies, pubic lice (crabs), hepatitis and HIV.

If you think you have been exposed to an STI, it’s a good idea to talk to your GP or sexual health service about having a check-up, even if you do not have any signs or symptoms of an STI. Don’t try to diagnose your symptoms yourself, and remember that not all genital signs and symptoms are caused by an STI.

Symptoms of STIs

There are many different STIs and there are many signs that mean you may have contracted one, but sometimes, there are no signs at all. When STIs do produce symptoms, they usually develop on the genital area. Your sexual contacts may also experience symptoms.

Generally, the symptoms of STIs can include: 

  • unusual discharge from the penis, vagina or anus
  • pain during urination
  • sores, blisters, ulcers, warts or rashes in the genital area
  • pain in the scrotum or testicles
  • lumps and bumps on the genitals.

Many people who have an STI do not develop any symptoms and may not be aware they have an infection that can be passed on to their sexual partners. This is why check-ups are so important.

STIs are passed on during sex

The most common sexual activities that can spread an STI from one partner to another include: 

  • vaginal sex – the man’s penis in the woman’s vagina 
  • anal sex – the man’s penis in the partner’s anus (the partner can be either male or female)
  • oral sex – the man’s penis in the partner’s mouth, or the partner’s mouth or tongue in the woman’s vagina
  • oro-anal sex – one partner’s mouth or tongue on the other partner’s anus.

STIs can also be passed from mother to child during pregnancy and at birth.

Diagnosis of STIs

The only way to find out if you have an STI is to have a sexual health check-up. GPs deal with sexual health problems on a daily basis, so don’t be embarrassed to ask for help.

Sexual health check-ups are easy to do. In most cases, it involves only a simple urine test. Some infections can be diagnosed on the day and treated at the time of your visit. Other results may take up to a week. 

Testing for STIs

For people with no symptoms, testing for STIs depends on how sexually active you are and whether you use condoms consistently. It is recommended that you get tested: 

  • after any sexual contact with a new or casual sexual partner 
  • after any sex, if you know or suspect that your partner has had other sexual partners
  • after any unwanted or non-consensual sexual contact
  • after any sexual contact in countries where HIV and other STIs are common
  • if your partner tells you that they have been diagnosed with an STI.

If you are a gay man or a man who has sex with other men, it is important to get regular check-ups for STIs, including HIV and syphilis, at least every year. Have more frequent (three-monthly) check-ups if you have an increased number of sexual partners (for example, more than 10 partners in three months).

If you are planning or having a family, it is also important that you and your partner have an STI test to prevent any infections being passed onto your baby.

How to reduce your risk of STIs

You can prevent most STIs by using barrier protection such as condoms, female condoms and dams (a thin piece of latex placed over the anal or vaginal area during oral sex). 

Most people are familiar with condoms for men. The female condom is a 14 cm, pre-lubricated sheath that fits loosely into the vagina and can be put in up to eight hours before sex. Female condoms should not be used together with male condoms because the friction between the two may cause the condoms to break. 

Dams are rectangular sheets of latex that can be used to cover the vagina or anus to prevent the exchange of bodily fluids during oral sex. They are sometimes called dental dams because they are also used during dental surgery.

Condoms for men can be bought from supermarkets, pharmacists and other outlets. Female condoms and dams are available through Family Planning Victoria and may be available from selected shops. Latex-free condoms are also available from some outlets. Male condoms and lubricant are available free from the Melbourne Sexual Health Centre. Female condoms and dams are available on request. 

Using condoms and dams

Condoms and dams are effective in helping prevent the spread of most STIs if they are used every time you have sex.

Some tips for correct use include: 

  • Use well-known brands and check the expiry date.
  • Store in a cool, dry place away from direct sunlight.
  • Make sure the condom or dam is free of holes or breakage before use.
  • Use water-based lubricants such as KY. Don’t use Vaseline, baby oil or massage oils, which can weaken and split condoms or dams.
  • Use each condom or dam once only.
  • Use dams for oral sex only – do not use as protection for anal or vaginal sex.

Treatments for STIs

Many STIs are easily treated once they are diagnosed. Treatments for the different types of infections can include: 

  • bacteria (including chlamydia, gonorrhoea, Mycoplasma genitalium and syphilis) require treatment with antibiotics 
  • parasites (including pubic lice and scabies) require treatment with medicated shampoos
  • viruses – (including genital herpes, HIV, hepatitis B and human papillomavirus (HPV)) do not have a cure. In most cases, there are treatments to help control the growth of the virus and help prevent symptoms.

Contacting sexual partners

Your sexual contacts may or may not experience signs and symptoms of an STI. If you have an STI it is important to contact any sexual partners you have had in the last three to six months, so they can get tested and have treatment if necessary. This is an essential part of reducing the spread of STIs in our community. 

Most people will prefer to be told that they might have an STI, as often they are unaware of it. Your GP or sexual health service can help you contact partners or you can contact them anonymously via Let Them Know. Let Them Know can send an anonymous email or text message informing a person that they have been a sexual contact of someone with an STI.

Where to get help


More information

Sexually transmissible infections

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This page has been produced in consultation with and approved by: Melbourne Sexual Health Centre

Last updated: February 2018

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