Medically reviewed by
Dr Nicholas Comninos, General Practitioner, Western Sydney Local Health District
What are sexually transmitted infections?
A sexually transmitted infection (STI) is an infection you get or give during sexual activity. STIs can be caused by viruses (e.g. human immunodeficiency virus, herpes), bacteria (e.g. gonorrhoea, syphilis) or parasites (e.g. pubic lice).
The prevalence of all STIs is not known because the infections aren’t always diagnosed. In 2024 there were more than 86,000 cases of Chlamydia, Gonorrhoea and Syphilis among Australian males. STI rates are higher in men aged in their 20s and 30s than in other age groups. Aboriginal and Torres Strait Islander males have higher rates of these infections than non-indigenous males. The rates of some STIs (eg Gonorrhoea and Syphilis) have been rising steadily in Australia for over 10 years.
Symptoms of STIs
The symptoms of STIs depend on the bacteria, virus or parasite that cause them.
Some STIs don’t have any symptoms, so you may not know you have one and might pass it on to someone else without knowing.
Causes of STIs
STIs are caused by bacteria, viruses or parasites that are transmitted during oral, anal or vaginal sex. For some infections, transmission can occur by close skin to skin contact (e.g. sexual intercourse).
Diagnosis of STIs
To diagnose an STI, your doctor will ask about your sexual history and practices, examine you if relevant to your care, and order tests to look for infections.
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Treatment of STIs
The treatment for STIs depends on what causes them. Usual treatments include antibiotics, antiviral medications and creams.
Health effects of STIs
Apart from the short-term effects, some STIs can impact on your reproductive system and even affect your ability to have children. STIs are readily treatable, but some infections can have lasting effects on your health and require long term medication / treatment.
What to do about STIs
The best way to deal with STIs is to practise safe sex so you avoid infection in the first place.
You should have regular sexual health checks. These should be more frequent if you’re sexually active and have new or different partners.
If you have symptoms of an STI, see your doctor straight away. You should avoid sexual contact with someone else in case you give the infection to them.
You should also speak to your sexual partner(s) to let them know you might have an STI so they can arrange to see their doctor.
Useful websites
STI testing
Testing for sexually transmissible infections
