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Sexually transmitted infections (STIs)
Find out more about the most common STIs.
Caroline avatar
Written by Caroline
Updated over a week ago

According to the World Health Organisation, more than 1 million STIs are acquired every day. Transmitted through sexual contact, they aren't always symptomatic and many people can have an STI without ever knowing. There are eight STIs which are seen as the most common, four of which are curable and four which aren't. So before you hop into bed with someone new, it's important to get an STI check-up and make sure you're aware of these common infections.


Chlamydia is considered to be the most common STI in Australia, with nearly 97,000 cases reported in both men and women each year. It's transmitted through unprotected sex and while some people may show symptoms, a lot of people don't, and you won't know that you or your partner have it. If symptoms do appear, they usually pop up around seven to 14 days after you have unprotected sex.

Symptoms can include:

  • Abnormal discharge

  • A burning or stinging when urinating

  • Pain during sex

  • Bleeding or spotting between periods

  • Sore or swollen testicles

Chlamydia can be treated with a single dose of antibiotics, if left untreated it may lead to pelvic inflammatory disease in women which can cause infertility.

You can find out more information about chlamydia here.


Gonorrhoea, or commonly called the 'clap', is spread through unprotected sex and can often go undetected in women with no symptoms. There's also the chance where the infection can affect the throat, resulting in oral gonorrhoea.

Symptoms can include:

  • Unusual discharge

  • Pain or burning sensation while urinating

  • Pain during sex

  • Sore or swollen testicles

Gonorrhoea can also be treated with a dose of antibiotics and may lead to pelvic inflammatory disease in women, which may result in infertility if no treatment is sought out.

You can find out more information about gonorrhoea here.


Syphilis can be transmitted through unprotected oral, vaginal or anal sex and can spread through skin-to-skin contact if a syphilis rash is present on the body.

There are three stages of a syphilis infection. Stage one usually happens over four to 12 weeks where a painless sore appears, usually on the genital area. The second stage happens around two to four months after acquiring the syphilis infection if treatment isn't sought out.

Symptoms can include:

  • Swollen lymph nodes

  • Joint pain

  • Flu-like illness

  • A red skin rash that may present on the soles of your feet and palms of your hands, but it can also cover your whole body.

The third stage of a syphilis infection can happen 10 to 30 years after the first infection and can affect various organs, causing serious complications which could result in death. Penicillin is used to treat syphilis, and it's important to have repeat blood tests done to check that the treatment has worked and that the syphilis infection has gone away.

You can find out more information about syphilis here.

Human Papillomavirus (HPV)

HPV is an extremely common incurable STI and according to Family Planning NSW, it's estimated that up to 80% of people in Australia will have HPV at some time in their lives. HPV is spread by skin to skin contact during sexual activity and can cause genital warts and certain types of cancers such as cervical cancer.

Most people don't know that they have HPV as it usually doesn't cause any symptoms, but genital warts can occur depending on what kind of HPV is present. High-risk types of HPV may lead to different types of cancer if left untreated, including cervical, anal and vaginal cancer, cancer of the vulva and penis, and cancers that affect the back of the throat.

While there is no treatment for HPV, the virus will usually leave the body over time, generally around a year or so. You'll need to get retested to see if the virus has gone from your system. You can also get vaccinated to protect yourself from getting the high-risk strains of HPV that most commonly cause cancer, but the vaccine doesn't protect you from them all.

You can find out more information about HPV here.

Genital Herpes

Genital herpes is a common STI that's caused by the herpes simplex virus (HSV). There are two types of the virus: HSV-1 and HSV-2.

HSV-1 is most commonly associated with cold sores on the lips or face and doesn't have to be transmitted solely through sexual contact for it to spread. According to Family Planning NSW, up to 80% of Australians carry HSV-1.

HSV-2, is mainly responsible for genital herpes. It transmits through unprotected sex, with one in eight sexually active Australians carrying the virus.

Genital herpes is transmitted through skin-to-skin contact, though it can also be spread asymptomatically when there are no sores present on the skin. Outbreaks can last for seven to 10 days and most people find that the outbreaks become less frequent over time. It can even be inactive in the body for long periods of time without any outbreaks and people may not know that they actually carry the virus.

If symptoms are present, they may include:

  • Stinging or tingling in the affected area

  • Small fluid-filled blisters or sores

While genital herpes can't be cured, there are treatments to manage the symptoms which may arise when your body is under stress. Antiviral tablets are given to help control any outbreaks that may occur and can be used to lessen the chance of asymptomatic shedding.

You can find out more information about genital herpes here.


Trichomoniasis is a common infection that's transmitted through sexual contact. It's more common in women than in men and while some may not have any symptoms, others may.

Symptoms can include:

  • An unpleasant odour

  • Vaginal itching

  • A yellow green discharge

Antibiotics are used to treat the infection and while it should get rid of it, there is a chance that trichomoniasis can reoccur. In this case, your doctor may prescribe a longer course of medication to get rid of it fully.

You can find out more information about trichomoniasis here.

Hepatitis A

Hepatitis is a viral infection that affects the liver and there are several different types of hepatitis that can be spread multiple different ways. The most common ones that are sexually transmitted are Hepatitis A, B and C.

Hepatitis A can be seen in the faecal matter and blood of someone that has the virus. While there are multiple other ways to contract the virus, it's commonly transmitted through sexual intercourse. If you do have the virus, you may see symptoms between 15 and 50 days after the initial infection.

Symptoms may include:

  • Nausea

  • Fever

  • Dark urine

  • Yellow skin

Hepatitis A does not cause long term liver disease, but it can cause inflammation and damage. There is a vaccine available to protect yourself from Hepatitis A and while it is an incurable condition, you can recover from the infection over a period of weeks or months.

You can find out more information about hepatitis A here.

Hepatitis B

Hepatitis B is spread mainly through unprotected sex and causes liver inflammation. It's spread through bodily fluids such as blood and semen, and left untreated can cause long term effects such as liver scarring, liver cancer and death.

Symptoms may include:

  • Nausea

  • Vomiting

  • Fever

  • Pain in the liver

  • Loss of appetite

Some people who contract hepatitis B can recover from the condition, though for others it can become chronic. The virus can't be cured but it can be prevented by vaccines. While there is no treatment for acute hepatitis B, chronic hepatitis B can be treated with medication, which will slow the progression of liver scarring and liver cancer.

You can find out more information about hepatitis B here.

Hepatitis C

Hepatitis C is a virus that causes damage to the liver and is spread through blood-to-blood contact. While it's more commonly spread through the use of drug injecting equipment, it can sometimes be spread through sexual contact. If left untreated, it can cause scarring of the liver and in small cases can lead to liver cancer.

Symptoms may include:

  • Tiredness

  • Nausea

  • Vomiting

  • Fever

  • Joint pain

  • Loss of appetite

Most people who are infected with Hepatitis C don't clear the infection from their bodies and carry the virus for more than six months, which leads to chronic hepatitis C. There's no vaccine available for hepatitis C, but it is treated with antiviral medications to try and clear it from the body.

You can find out more information about hepatitis C here.

Human Immunodeficiency Virus

Human Immunodeficiency Virus (HIV) is a virus that impacts the immune system, making it harder for the body to fight off infections. HIV can be spread through multiple ways, with one way being through unprotected sex. It's transmitted through bodily fluids including, blood, semen, vaginal fluid and breast milk.

Symptoms can include:

  • Fatigue and extreme tiredness

  • Fever, sweats or chills

  • Swollen lymph glands in the neck, underarm or groin areas

  • Weight loss

  • Diarrhoea

  • Skin rashes

  • Sore muscles and joints

If no treatment is sought, most people will develop severe immune deficiency within 10 years. This can lead to Acquired Immunodeficiency Syndrome (AIDS), where people will be more likely to develop diseases and serious conditions.

While there is no vaccine or cure for HIV, there are treatments (such as PrEP and PEP) that can help to prevent the transmission of HIV and the occurrence of AIDS, allowing people to live a near-normal life expectancy.

Antiretroviral therapy (ART) is another treatment that stops the virus from reproducing itself. By taking it daily, HIV can become a manageable chronic condition.

You can find out more information about HIV here.

How can STIs be prevented?

To avoid contracting an STI, it's important you're practicing safe sex, this includes the following:

  • Know the STI status of your sexual partner, ask them when the last time was that they were tested, what their results were, and make sure you get tested as well. Remember not everyone knows they have an STI and you can't determine if someone has one just by looking.

    • It's also important to know that not every STI is tested for in a normal STI check. The genital herpes virus isn't normally included and HPV can only be detected by a pap smear. There is also no test for men to find out if they test positive for HPV.

  • Use a condom or other barrier methods every time you have vaginal, anal or oral sex.

  • Get vaccinated against STIs, such as Hepatitis A and B and HPV.

  • Consider PrEP, a medication that someone who is HIV negative can take to reduce their risk of contracting HIV from a HIV positive partner.

If you think you have symptoms of an STI, make sure you visit your GP or have a confidential chat to one of our Sonder team members who can help provide support and advice. Or you can access one of these sexual health helplines below for more information.

Sexual health helplines

  • Sexual Health Helpline - 1800 198 205

  • HealthDirect Hotline - 1800 022 222

  • NSW Sexual Health Infolink - 1800 451 624

  • WA Sexual Health Helpline - 1800 198 205

  • Shine SA Sexual Health Helpline - 1300 883 793

  • QLD Sexual Helpline - 13 43 25 84

  • TAS Public Health Hotline - 1800 671 738

  • VIC 1800 My Options - 1800 696 784

Related readings:

If you have any questions or need extra support, we're here to help you anytime in any language. Simply start a chat with us via the home screen of the Sonder app.

Image credit: Parks and Recreation

All content is created and published for informational purposes only. It is not intended to be a substitute for professional advice. Always seek the guidance of a qualified health professional.

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