Can you pass on Syphilis without a sore?

Syphilis is a bacterial infection caused by a bacterium called Treponema pallidum. These transmit from person to person mostly through sex but also through routes like other blood-to-blood contact, such as by sharing needles.

Once thought to be an infection of the past, going the way of smallpox and the plague, Syphilis has made a resurgence in recent years as the bacteria people become less concerned about its transmission, thinking it’s so uncommon. Also it has a predilection for anal sex as its preferred route of transmission and unprotected anal sex is more common than 20 years ago. This STI is one of the most common in Australia. We see more antibiotic resistance than before in some syphilis strains.

If left untreated, Syphilis can cause a host of negative health outcomes. It has an uncanny ability to remain latent in your body for long periods of time. When it does show symptoms, they can be confused with other medical problems and people infected may not see medical help. Although it’s easy to stop Syphilis in its tracks with penicillin, if symptoms are left to progress the final stage may cause damage to vital organ systems like the brain, heart, bones, eyes, and nervous system. even blindness, deafness, heart disease, and eventually death.

Although easy to treat with antibiotics, you can catch Syphilis more than once – there is no lifelong immunity against the bacteria.

In the initial stages of a Syphilis infection, the infected person may develop a sore or ulcer at the site of infection – usually the genitals, anus, or mouth. These sores are known as chancres.

Chancres tend to be firm, round, and painless. Although the size of the chancre can vary from person to person, it tends to be fairly small. Because it is painless, it often goes unnoticed. An infected person usually has just one chancre, but sometimes there may be more than one.

Chancres appear after a minimum of 10 days of contracting the infection but can appear as late as 90 days after getting it. They tend to go away three to six weeks after they first appear, even with no antibiotic treatment. But this doesn’t mean the patient is cured, rather that it is moving round the body.

The appearance of chancres is usually followed several weeks later by other symptoms, such as:

• A generalised skin rash that looks a bit like measles
• Rarely., a skin rash on the palms of the hands or soles of the feet
• Fever
• Weight loss
• Fatigue
• Muscles aches
• Headaches
• Swollen lymph nodes
• Unexplained hair loss

These symptoms usually resolve within a few weeks, again, without treatment. After that, if left untreated, the infection enters its advanced where it may eventually damage various organ systems.

Syphilis is very contagious and is easily passed between people through sexual activity, especially unprotected vaginal, anal, and oral sex.

Person-to-person contact with a chancre is one of the most effective ways of contracting the infection. Although genital-to-genital contact is most often the case, any physical contact with a chancre has been described as potential ways to spread the infection.

One of the things that makes STIs so pernicious is their ability to go undetected. Most STIs don’t cause any symptoms, and many cause symptoms that are so mild they go unnoticed or are confused with other, less serious infections.

Just because you do not notice any symptoms of an STI doesn’t mean you don’t have one. That’s why all sexually active people need to get tested regularly.

In the stage with a generalised infection and skin rashes (secondary Syphilis), the patient is very infectious but has not sores at all.

Syphilis is treated using antibiotics – usually penicillin in the form of an injection. Even though we mentioned earlier that some strains of syphilis as now resistant to other antibiotics, thankfully they are all easily treated with penicillin. Syphilis infections are simple to cure when they’re caught in the early stages. More developed cases of Syphilis may require a longer course of antibiotics or special regimes.

Syphilis can be contagious for a short time after treatment. Most people may need to wait a week or more after they finish treatment before they can think of engaging in any sexual activity. Engaging in sexual activity before this time may result in spreading the infection. Generally, it may be a good idea to wait until you have no symptoms at all before starting to have sex again.

Most people wish to get added testing after treatment to ensure they’re free of the infection. This is to ensure the treatment has been effective and that they are no longer contagious. We usually wait a few months to do this test, but in the meantime, the chance your treatment had failed and that you could pass on the infection is close to zero.

If you suspect you may have an STI, or you think you may have been exposed to one, you should get tested.

Call the number at the top of this page to speak to one of Better2Know’s trained Sexual Health Advisors. They can talk to you about your situation and help you come up with a plan of action that will protect your sexual health.

Or, if you would like to book an appointment online, click the button below to secure a sexual health screening at a clinic near you.

This article has been medically reviewed by Dr. Steve Chapman, 29/04/2025.