Clinical health information Sexually transmitted infections (STIs) September 11 2019

We take a look at different types of sexually transmitted infections (STIs), and their possible causes, treatment and prevention.

A sexually transmitted infection (STI) is a disease that can be transmitted by skin-to-skin contact, blood, semen, or vaginal and other bodily fluids during unprotected sex with an infected partner. 

About STIs

For more than a decade, there’s been an increase in the rates of certain STIs in Australia. Chlamydia is the most common STI, particularly in younger people — in 2017, 73 percent of reported cases were in those aged 15–29 years. However, simple measures can help reduce your risk of getting an STI and in many cases treatment is available. So it’s important to be informed.

Symptoms of STIs

STIs don't always have obvious symptoms, so it can be possible to be infected and not realise it. If you do have symptoms they might include:

  • an unusual discharge from your vagina, penis or anus
  • unusual vaginal bleeding 
  • sores, blisters, warts, rashes, lumps, irritation or itching near your genitals, anus or mouth
  • pain or burning sensation on passing urine
  • pain during sex
  • pelvic or lower abdominal (tummy) pain
  • pain in the testicles or scrotum. 

It's important to be tested if you think you may have an STI. If untreated, some STIs may lead to complications and serious health problems, such as infertility or cancer.

Causes of STIs

Most STIs are caused by micro-organisms such as bacteria, viruses or parasites. These infections can be passed from one person to another during intimate physical contact, such as through sexual intercourse, non-penetrative genital contact, sharing sex toys with partners and oral sex. It’s also possible for some of these infections to be passed non-sexually (e.g. from mother to baby during pregnancy or childbirth, or via blood transfusions or shared needles).

Diagnosis of STIs

If you think you may have an STI, it’s important to see your GP to get tested. STI testing is also offered in many other places such as sexual health clinics, family planning clinics, women’s health centres and youth health centres. You don't have to ask your GP to refer you to a sexual health clinic or other health centre; you can make your own appointment. There are also some online services available in certain states (e.g. TESTme).

All visits are confidential — in Australia, healthcare professionals are required by law to keep your health information private. However, there are some situations where they may have to report information. For example, if they have serious concerns about your, or someone else’s, safety. If you’re unsure about how confidentiality in healthcare works, ask at the beginning of your consultation. 

STI testing usually involves a physical examination, which for women may include an internal examination. Swabs (to get cells or traces of infection) and blood, urine or saliva samples may also be taken. It may be possible to provide self-collected vaginal or anal swabs if you prefer. You may also be asked some questions about your general health and sexual health. 

If you do test positive for an STI, you should get treated as soon as possible (this is usually straightforward) and tell your sexual partner(s) so they can get tested and treated too.

Types of STIs and how they’re treated

Some common STIs are discussed in more detail below.


In Australia, chlamydia is the most common STI and it often affects people aged between 15 and 29 years, as they may be more likely to change sexual partners. It's caused by a type of bacteria that can infect the cervix (the neck of the womb), urethra (the tube that carries urine from your bladder and out through the penis or vulva), rectum (back passage), throat and/or eyes.

In women, symptoms include: 

  • lower abdominal pain
  • bleeding after sex 
  • bleeding in between periods
  • unusual vaginal discharge
  • pain when passing urine. 

In men, symptoms include: 

  • discharge from the penis
  • pain when passing urine
  • pain and swelling in the testicles. 

Symptoms usually occur one to two weeks after getting infected. However, it’s estimated that about 70 percent of women and 50 percent of men with the infection don't have any symptoms.

If you have a rectal infection there are rarely any symptoms, but you may have a discharge and it can be painful.

Chlamydia can be treated with antibiotics.

Genital herpes

Genital herpes is caused by the herpes simplex virus (HSV). A genital herpes infection usually causes painful ulcers or sores in or around the genital area, anus, buttocks or thighs. These may develop about 2 to 12 days after infection. You may also have pain when you pass urine, a stinging or tingling in your genital area or feel generally unwell (e.g. flu-like symptoms). Some people don't have any symptoms or have sores that aren't painful.

After the first or primary episode, you may have repeat attacks of herpes — this is because the virus lies dormant (sleeping) in your body for the rest of your life. Recurrences don't tend to be as severe as the first attack and or last as long.

There’s no treatment to remove the herpes virus from your body. However, your doctor can prescribe antiviral tablets. If taken early enough, these medicines can help the outbreak clear up faster and reduce the severity of your symptoms.

Genital warts

Genital warts are a very common STI and are caused by certain strains of the human papilloma virus (HPV). The warts are fleshy growths that usually appear on or around the genitals and anus.

They can also occur in the mouth and throat. 

They are usually painless but can itch and may bleed or become inflamed. It may take a few weeks or months for warts to appear after you're infected, but it can take much longer.

Warts sometimes disappear without treatment, but it may take many months. However, they can be treated with a chemical solution or liquid nitrogen (cryotherapy). Surgery or laser treatment are also options, although sometimes repeat treatments are necessary. These types of treatment only target the visible warts; they do not remove the virus from your system. 

The HPV vaccine can offer protection against some of the strains of HPV that cause genital warts, although its suitability will depend on a person’s age and sexual history.


Gonorrhoea is caused by bacteria that can infect the urethra, cervix, rectum, and, less commonly, the throat and eyes. Symptoms can appear within about 2 weeks of becoming infected or not until many months later.

In women, symptoms can include an unusual vaginal discharge, pain when passing urine, lower abdominal pain, bleeding between periods or heavier periods. However, around half of all women with gonorrhoea may not have any symptoms. Symptoms in men can include a white, yellow or green discharge from the tip of the penis and pain when passing urine. About 10 percent of men may not have any symptoms.

If your throat is infected you probably won't have any symptoms. This is also true if your rectum is infected, but occasionally it can cause discharge, pain or discomfort.
Gonorrhoea can be treated with antibiotics. As with chlamydia, gonorrhoea can cause serious health and reproductive problems if it isn't treated, so it is important to seek the advice of a healthcare professional.

Hepatitis B

Hepatitis B is caused by a virus (HBV) that is highly infectious. Symptoms of hepatitis B can appear about one to six months after you become infected and include dark urine, extreme tiredness, loss of appetite, feeling or being sick, abdominal pain, fever and jaundice (yellowing of the skin and eyes). HBV can also cause a chronic liver infection that can later develop into cirrhosis or liver cancer.

Some people with hepatitis B never have any symptoms. They are known as asymptomatic carriers as they are still infectious and can unknowingly pass on the disease to others.

Some people with acute hepatitis B may recover without treatment. If treatment is required, the type of medicine given depends on how long the person has been infected (i.e. whether the infection is acute or chronic). There are different medicines available such as antivirals or those that help your immune system fight the disease. A vaccine is also available to prevent the disease. 


The human immunodeficiency virus (HIV) attacks your immune system. Most people have flu-like symptoms within a few weeks of being infected.
Infection with HIV can lead to Acquired Immune Deficiency Syndrome (AIDS). If HIV infection is left untreated over a long period of time, it can damage a person's immune system and put them at high risk of developing related infections or cancers. At this advanced or late stage of HIV infection, a person is said to have AIDS. 

There is currently no cure for HIV infection. However, doctors can prescribe antiretroviral treatments to help reduce the level of virus in the blood — this aims to help the immune system repair itself and reduce further damage. 

There are also emergency HIV medicines available known as ‘post-exposure prophylaxis’ (PEP). PEP is not for everyday use, but for people who think they may have been exposed to HIV during high-risk scenarios. PEP must be started within 72 hours of HIV exposure and aims to help stop the infection taking hold. 

Pubic lice

Pubic lice mainly live in your pubic hair but they can infect other body hair including eyebrows and eyelashes. They lay eggs (nits) that stick to your hairs.

Symptoms include itchy red spots and you may also notice black powdery spots from the lice in your underwear. It can take several weeks after infection for symptoms to appear.

Pubic lice can be treated with lotions or shampoos.


Syphilis is a bacterial infection. It's less common in Australia, although rates have been increasing in certain populations.

The first sign of syphilis in the primary stage is a painless sore or lump usually found on or near the genitals, mouth or anus — wherever you were first infected. This can develop around two to three weeks after infection. In the secondary stage of the illness, you may feel generally unwell with flu-like symptoms and a rash. This stage may last for a few weeks or may come and go over several months.

These symptoms may gradually clear up on their own, but it's important to treat syphilis as soon as possible. Over time it can cause major health problems, such as damage to your heart, brain, nerves, eyes, blood vessels, liver, joints and bones.

Syphilis can be treated with antibiotics in tablet form or as an injection.

Prevention of STIs

Simple measures can help reduce your risk of catching an STI. Safer sex methods include using barriers such as male condoms for vaginal, anal and oral intercourse and when sharing sex toys.

Other options include female condoms for vaginal sex and dams — thin sheets of latex — for vaginal or anal oral sex. These can help prevent the spread of HIV and reduce the risk of many STIs.

In Australia, the HPV vaccine was introduced in 2007. It’s currently free for girls and boys aged 12 to 13 years; but may be given at certain other ages at a cost, depending on suitability.

Vaccination gives the best chance of protection against HPV infection later in life.

If you're diagnosed with an STI it's important to contact your previous partners who may be at risk, to help prevent them from spreading the infection to others. If you’re uncomfortable doing this personally, sexual health clinics can send anonymous notifications on your behalf. There are also websites that offer this anonymous service (e.g. Let Them Know).

If you think you could be at risk of catching an STI, consider having a check-up with your GP or at a sexual health clinic or other health centre every few months. Once diagnosed with an STI, it's important to get treated and wait until you’re given the all clear before you have sex again.

Further information 

Check Your Risk:

Family Planning Alliance Australia:


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