Cases of infectious syphilis have increased in the past year by 45%, with 736 cases reported in New Zealand in 2023.

It’s the highest number of cases ever recorded in the Institute of Environmental Science and Research’s (ESR) yearly STI surveillance reports, up from 508 cases the previous year, according to a release from the New Zealand Sexual Health Society.

The report shows case numbers have nearly doubled among gay and bisexual men, while the numbers also show a rise in cases among women of reproductive age. The rates of infection for Māori and Pasifika people were double those of other ethnicities.

Auckland, Waikato and Canterbury have seen the most infections - and experts say there are likely many more cases that have gone unreported.

Infectious disease and sexual health doctor Massimo Giola told RNZ this week, “It is alarming, and unfortunately I think this is just the tip of the iceberg, so the problem out there is even bigger. First of all because not all syphilis cases are notifiable, and ESR only records the notifiable cases, so my best guess is [there’s] probably two to three times more syphilis around than those numbers indicate.”

Giola said it showed there was not enough testing taking place in communities around New Zealand.

Over a third of women diagnosed in 2023 were pregnant at the time, raising concerns for their reproductive health.

“Given that approximately only 5% of women in the reproductive age group are pregnant at any given time, this suggests there is a lot of undiagnosed syphilis.”

New Zealand Sexual Health Society president Dr Jeannie Oliphant said the infection could be “devastating” in pregnancy, “with around 40% of infected babies stillborn or dying soon after birth”.

“Given that approximately only 5% of women in the reproductive age group are pregnant at any given time, this suggests there is a lot of undiagnosed syphilis.”

Here, Sexual Wellbeing Aotearoa medical director Dr Beth Messenger explains the signs and symptoms of syphilis, how it’s diagnosed and treated, and how you can prevent infection from occurring.

What is syphilis?

“Syphilis is a sexually transmissible infection caused by a bacteria,” Messenger explains.

“It may start with an ulcer - although many people have no symptoms.”

While people who have unprotected sex are more likely to get other STIs - chlamydia, gonorrhoea or genital warts - syphilis is a very infectious STI.

“You can get syphilis from having unprotected vaginal sex, anal sex, oral sex, or close skin-to-skin contact with someone.”

How is it diagnosed and treated?

As many as half the people who have syphilis won’t have symptoms, meaning a blood test is required for diagnosis. It can take from 10 days to three months for signs or symptoms to become apparent, Messenger explains.

“This delay in symptoms becoming apparent is why it is so important to get regular STI tests,” she says. “If syphilis is left untreated, it can cause damage to the heart, brain and spinal cord.”

Test results typically take about a week to come back. If you are pregnant, you will be offered a blood test for syphilis among other STIs early on in your pregnancy.

Syphilis is treated with antibiotics, usually by penicillin injection.

What are the risks of getting syphilis?

Messenger says Kiwis “should be concerned” about the rise in syphilis and STIs in general.

“Untreated STIs can have long-term consequences for people and contribute to poor health,” she explains.

“Syphilis can be passed from a pregnant person to their pēpi through the placenta. It can cause miscarriage, stillbirth, or infection in the pēpi if it’s not treated.”

Due to health regulations in New Zealand, nurses at Sexual Wellbeing Aotearoa can’t order tests that require a blood test, meaning GPs need to sign off these requests.

“This puts real pressure on our doctors to oversee these nurse requests. A change to the regulations allowing nurses to request these tests would expand access to testing - and that can only be a good thing,” Messenger says.

Oliphant says it’s important to increase testing for syphilis in the community so that infections can be identified earlier.

“Syphilis is efficiently transmitted, is often unrecognised and already has a firm foothold ... this situation requires an urgent response and will need appropriate resourcing to prevent numbers continuing to increase.”

Syphilis is often asymptomatic and thus requires a blood test for diagnosis. Photo / 123RF

How can you avoid getting it?

Messenger says it’s important to use protection such as condoms or oral dams when you have sex or take part in sexual activity.

“It’s a good idea to make sure that you know how to use them correctly - and that you use them every time you have sex.”

However, it’s important to note condoms are not completely protective against syphilis, according to New Zealand’s official STI management guidelines.

“If you are going to have unprotected sex, it’s really important that you, and the person you are going to have sex with, both get STI tests before and after sex,” Messenger adds.