Sexually Transmitted Infections

What are sexually transmitted infections?

Sexually transmitted infections (STIs) are infections caused by some bacteria, viruses and other organisms. They can be passed from one person to another through any form of sexual activity, including vaginal, anal and oral sex. Some STIs can even be passed on just through close skin-to-skin contact.

This fact sheet gives a brief overview of each STI. For more detailed information, please see the individual fact sheets for each infection.

Chlamydia*

• Often has no symptoms.
• May cause the following symptoms:
  • Burning or pain when urinating (weeing)
  • Discharge from the penis or vagina
  • Pain in the testicles (balls)
  • Pain in the lower abdomen or pelvis
  • Bleeding between periods and/or after sex
  • Pain during sex
  • Pain or discharge from the anus (bottom)
• If chlamydia is left untreated, it can cause serious health problems such as:
  • Pelvic inflammatory disease (PID)
  • Swelling and pain in the testes (balls)
  • Infertility (difficulty getting pregnant)
• Diagnosed with a urine or swab test.
• Treated with antibiotics.

Gonorrhoea*

• Infections of the anus (bottom), throat or vagina often have no symptoms. Infection of the penis usually has symptoms.
• May cause the following symptoms:
  • Discharge from the penis or vagina
  • Burning or pain when urinating (weeing)
  • Pain during sex
  • Pain, irritation or discharge from the anus (bottom)
• If gonorrhoea is left untreated, it can cause serious health problems, such as:
  • Pelvic inflammatory disease (PID)
  • Swelling and pain in the testes (balls)
  • Infertility (difficulty getting pregnant)
• Diagnosed with urine and swab tests.
• Treated with antibiotics

HPV (Human Papilloma Virus)

• HPV is very common – anyone who has ever had any form of sexual contact can have HPV.
• May cause:
  • No symptoms
  • Lumps or warty growths in and around the anus (bottom) or genital area. These may be painless or cause some irritation/itch
• Certain types of HPV can cause cancer over a long period of time (for example, cervical cancer)
• Can spread through direct skin-to-skin contact.
• Vaccination can prevent some types of HPV.
• Visible warts can be removed by freezing them or applying a wart cream.

Genital Herpes Simplex Virus (HSV)

• Can be transmitted through vaginal, anal and oral sex, as well as skin-to-skin contact.
• Often causes painful sores or ulcers around the genitals or bottom, which scab over and heal
• The first episode is usually the most severe. Future episodes are usually milder and may be triggered by stress or illness. Some people never have another episode.
• Antiviral medication may be used to help prevent future outbreaks.

Mycoplasma Genitalium

• Often has no symptoms
• May cause the following symptoms:
  • Burning or pain when urinating (weeing)
  • Discharge from the penis or vagina
  • Pelvic pain or pain during sex
  • Bleeding in between periods and/or after sex
• If mycoplasma genitalium is left untreated, it can cause serious health problems including:
  • pelvic inflammatory disease (PID)
  • possible infertility (difficulty getting pregnant).
• Diagnosed with a urine or swab test.
• Treated with antibiotics.

Trichomonas

• Often causes no symptoms
• May cause the following symptoms:
  • Smelly, frothy vaginal discharge
  • Vulval itch, burning or soreness
  • Burning or pain when urinating (weeing)
• Diagnosed with a urine or swab test.
• Treated with antibiotics.

HIV (Human Immunodeficiency Virus)*

• HIV spreads through the exchange of body fluids (such as semen, vaginal discharge, or anal mucus during sex) or blood (for example, by sharing needles or injecting equipment).
• It can also be passed from a pregnant to a baby during pregnancy, childbirth or breastfeeding – but medications can greatly reduce this risk.
• Some people experience a flu-like illness soon after infection.
• Without treatment, HIV weakens the immune system over time.
• HIV is diagnosed with a blood test.
• Treatment and prevention:
  • There’s no cure yet, but antiretroviral medication can stop the virus from damaging the immune system.
  • With early and ongoing treatment, people with HIV can live long, healthy lives.
  • Post Exposure Prophylaxis (PEP) is a short course of HIV medication that can prevent infection if started within 72 hours of exposure (the sooner, the better). Call the PEP Hotline: 1800 022 226.
  • Pre Exposure Prophylaxis (PrEP) is a daily pill for HIV-negative people that greatly lowers the risk of getting HIV.

Syphilis*

• Mainly spread through direct contact with sores or rashes from someone who has the infection. It can also spread through contact between the mouth, genitals or anus (bottom).
• The first sign is often a painless sore(s) on the mouth or genitals.
• Later symptoms may include a skin rash, patchy hair loss, feeling unwell or moist lumps around the genitals or anus (bottom).
• If left untreated, these symptoms may go away but complications can develop months or years later, including severe skin sores, heart problems and brain/nerve damage.
• Syphilis can also be passed from a pregnant person to their baby.
• Diagnosis is made with a blood test (and sometimes a swab).
• Treated with antibiotics (usually an injection).

Hepatitis B*

• Hepatitis B is passed through blood and other bodily fluids. This can happen during unprotected sex, sharing needles or other injecting equipment, using unclean tattoo or piercing tools, or sharing personal items like toothbrushes, razors or nail clippers.
• Many people don’t have symptoms at first but can still pass the virus to others.
• A pregnant person can pass Hepatitis B to their baby.
• If not treated, it can cause serious liver problems, including liver failure or liver cancer.
• Medicines can help control the virus. Some people get rid of it naturally, but everyone with Hepatitis B should have regular liver check-ups.
• Diagnosed with a blood test.
• There is a safe vaccine that can prevent you from getting Hepatitis B.

Hepatitis A

• Hepatitis A can spread when tiny amounts of infected faeces get into the mouth, for example during anal-oral contact (directly or via fingers), or through contaminated food and water.
• It can affect the liver and cause tiredness, fever, nausea, stomach or joint pain, dark urine, yellowing of the skin or eyes (jaundice) and loss of appetite.
• People who have anal or oral sex are advised to get vaccinated to reduce the risk of infection.
• Diagnosed based on symptoms and a blood test.
• There is a safe vaccine that can prevent you from getting Hepatitis A.

Hepatitis C

• Hepatitis C affects the liver and can cause serious damage if not treated.
• It is mainly spread through blood-to-blood contact, such as sharing needles, or using unclean tattoo or piercing equipment. People who had blood transfusions before 1990 may also be at risk.
• Sexual transmission is rare but the risk is higher if HIV or other STIs are present.
• There is currently no vaccine for Hepatitis C.
• Diagnosed with a blood test.
• Medicines can cure most people with Hepatitis C.

* Notifiable STIs

Gonorrhoea, Syphilis, HIV and Hepatitis B are notifiable infections. This means that if a test comes back positive, the doctor or nurse must inform the Communicable Disease Control Branch (SA Health).

If you are diagnosed with one of these infections it is important to contact your sexual partners from the last 3-6 months (depending on the infection). If needed, there are websites that can assist you so these partners can be contacted anonymously to let them know they may be at risk and need testing or treatment.

This is a very important step as it will prevent these infections from being passed on to others.

Prevention of STIs

• Use condoms for vaginal, anal and oral sex.
• Talk about any past infections with your sexual partner/s.
• Get tested regularly – at least every year or with a new sexual partner.
• Don’t share needles, tattoo equipment, or anything that comes into contact with blood If you have sores, lumps, ulcers or unusual discharge around the mouth or genitals, avoid sex or any skin-to-skin contact with the affected area until it heals.

Non STIs

Some infections that are not sexually transmitted can also cause discharge, such as Bacterial Vaginosis or Candida (Thrush). These conditions do not always need treatment, but you should see a healthcare professional if you notice unusual changes or are concerned.

When to get an STI test

• If you notice any symptoms of an STI.
• If a sexual partner is diagnosed with an STI or has symptoms.
• Even without symptoms, you can get a check-up with your GP or sexual health clinic.
• Routine STI screening is recommended if you have a new sexual partner or if your partner has had a new sexual contact.

Updated December 2025.