The top 5 STIs in Australia, and how to protect yourself

STIs remain a significant public-health challenge in Australia, and stigma and low awareness mean many cases go undetected. STIs can be caused by viruses, bacteria or parasites, and are usually spread during sexual activity. There are many types, but five are the most common here. Knowing the basics helps you protect your health.

Chlamydia

Chlamydia is the most common STI in Australia, particularly in people aged 15 to 29. It’s caused by the bacterium Chlamydia trachomatis and can affect the urethra, throat, anus, eyes, cervix and testicles.

How you get chlamydia

It spreads through skin-to-skin contact during vaginal, anal or oral sex with someone who has it, and can also pass on by sharing sex toys or rubbing genitals together. It’s transmitted when infected genital fluids reach a mucous membrane, such as those lining the vagina, penis or rectum.

Symptoms of chlamydia

Most people notice nothing at all. When symptoms do appear, they can include:

• smelly or unusual discharge from the penis, vagina or anus
• burning or discomfort when passing urine
• pain in the lower abdomen, testicles or rectum
• pain during sex, or bleeding from the vagina after sex
• redness at the opening of the penis, or conjunctivitis.

Complications and treatment

Left untreated, chlamydia can cause pelvic inflammatory disease (PID), infertility, chronic pain or ectopic pregnancy in women, and testicular pain, infertility or reactive arthritis in men. It’s cured with antibiotics, but you don’t become immune, so re-infection is possible. See our full guide to the long-term risks of chlamydia, or book a chlamydia test.

Syphilis

Syphilis is caused by the bacterium Treponema pallidum and has risen sharply in Australia over the past decade, but it’s easily treated in its early stages. It spreads through skin-to-skin contact during vaginal, anal or oral sex, through rubbing genitals or sharing sex toys, and can pass to a baby in pregnancy.

The four stages of syphilis

Syphilis progresses through stages, and the symptoms change at each one:

• Primary: one or more painless sores (an ulcer, or “chancre”) where the infection entered — often the genitals, anus or mouth. These heal on their own, with or without treatment.
• Secondary (about 4 to 10 weeks later): a rash, classically on the palms and soles but also the chest and back; white or grey lesions in the mouth or genital area; swollen lymph nodes; fever; fatigue; headache; and patchy hair loss.
• Latent: no symptoms, but the infection is still present and can progress.
• Tertiary (late): if untreated, serious damage to the heart, brain, nerves and other organs — including heart disease, neurological problems (headaches, poor coordination, paralysis, numbness, dementia), vision loss, and soft growths on the skin, bones or organs.

Complications and treatment

Untreated syphilis can cause permanent organ damage, neurological problems, or even death, and in pregnancy it can lead to miscarriage, stillbirth or serious harm to the baby. It’s treatable with antibiotics, but you don’t develop immunity, so re-infection is possible. A syphilis test detects it early, when treatment is simplest.

Gonorrhoea

Gonorrhoea is caused by the bacterium Neisseria gonorrhoeae. It’s highly contagious, has climbed steeply over the past decade, and affects Aboriginal and Torres Strait Islander peoples around five times as often as non-Indigenous people. It can affect the urethra, rectum, throat, eyes and cervix, and spreads through vaginal, anal or oral sex, sharing sex toys or genital-to-genital contact.

Symptoms of gonorrhoea

Symptoms differ between men and women, and many people have none. Women may notice:

• unusual vaginal discharge
• pain when passing urine, or pelvic pain
• irregular vaginal bleeding, or pain during sex.

Men may notice discharge from the penis, pain passing urine, pain or swelling of the testicles, or redness at the opening of the penis. If the anus is infected, either can have rectal pain.

Complications and treatment

Untreated, gonorrhoea can cause PID, chronic pelvic pain, infertility and ectopic pregnancy in women (and can pass to a baby at birth), and testicular pain, prostate inflammation and infertility in men. Rarely, it spreads to the skin, joints, blood and other organs. It’s treated with antibiotics, usually an injection plus oral antibiotics because of rising resistance. See how it compares in chlamydia vs gonorrhoea, or book a gonorrhoea test.

HPV and genital warts

HPV (human papillomavirus) is very common, with more than 200 types. Some cause genital warts, while a few high-risk types are linked to cancers, particularly cervical cancer. Most sexually active people will get at least one type at some point, and it usually passes on when someone has no symptoms and doesn’t know they carry it.

Symptoms and complications

Most people have no symptoms. When present, some types cause genital warts (flesh-coloured lumps in the genital area), itching or discomfort, or abnormal bleeding. The immune system clears most HPV infections within about two years, and clearing one type usually gives immunity to it (though you can still catch others). A small number of persistent high-risk infections can lead to cancer over time, which is what cervical screening is designed to catch.

Treatment and prevention

Warts are treated by freezing (liquid nitrogen), prescription creams, or occasionally laser. Prevention is strong: the HPV vaccine is free for young people aged around 12 to 13 under the National Immunisation Program, with free catch-up up to age 26, and cervical screening — now a simple self-collect test — checks for high-risk HPV.

Genital herpes

Genital herpes is caused by the herpes simplex virus, usually HSV-1 (which also causes cold sores) or HSV-2. It spreads through skin-to-skin contact with the affected area during vaginal, anal or oral sex, or through rubbing genitals or sharing sex toys.

Symptoms of herpes

Most people never notice symptoms. When they occur they can include:

• painful blisters or sores on the genitals, anus or mouth
• burning, itching or tingling in the area
• splits or cracks in the genital skin
• pain passing urine, or pain during sex
• fever and swollen glands.

Complications and treatment

Once you have HSV, the virus stays in the nerve pathways and outbreaks can recur, often when you’re stressed, run down or unwell. There’s no cure, but antiviral medication manages outbreaks well. Herpes needs care in pregnancy, as it can rarely be passed to a newborn during birth. A herpes test and a chat with a Specialist GP can help you understand and manage it.

How to avoid an STI

STIs are common in Australia, but most are preventable with two simple habits: safer sex and regular testing.

Safer sex

Use condoms and dental dams with new or casual partners for vaginal, anal and oral sex, avoid sharing sex toys (and wash them thoroughly after use), and talk openly about testing and prevention, letting partners know if you’re ever diagnosed.

Regular testing

Because so many STIs cause no symptoms, a regular STI test is the only way to be sure. It’s worth testing with a new partner, if a condom slips or breaks, if you have symptoms, or if you’re pregnant or planning to be — and routinely (more often if you have multiple partners, or you’re a man who has sex with men).