Pregnant mothers are being asked to take steps to protect themselves as rates of syphilis increase.
The Ministry of Health and the Institute of Environmental Science Research (ESR) released figures today, showing a 41 percent increase in syphilis in the second half of 2022.
Across the regions, Auckland had the most cases at 309, more than double the cases reported in other areas of the country.
If untreated, the sexually transmitted infection can have impacts on the brain, and other organs and can increase the chance of HIV.
Pregnant mothers and their partners are the Ministry of Health's main concern, as unborn children are especially at risk.
Dr Julia Scott, Public Health Physician at ESR says syphilis in pregnancy can lead to stillbirths, congenital abnormalities and severe illness in babies.
Early symptoms to watch out for include sores and ulcers on the site of infection, usually genitals, anus or mouth.
People with the infection may also experience rashes, spots on their hands and feet, fevers, headaches and more.
Manatū Hauora Director of Public Health Dr Nicholas Jones is urging people to practice safe sex to prevent the spread of infection and get STI checks regularly.
"Syphilis infections have been rising globally including in New Zealand. People need to be aware that there is an increased risk of infection during sex and consequences can be serious."
The ESR data shows the rise in cases in late 2022 has been largely among men, with men who have sex with other men recording an 81 percent increase in 2022.
There was also a spike in syphilis cases among men who have sex with women, with a 76 percent increase.
Dr Julia Scott, Public Health Physician at ESR, says a concerning impact of the rising cases is the possibility it could be passed from mother to child during pregnancy, known as congenital syphilis.
"In Aotearoa, the number of cases of syphilis identified in pregnancy and in babies remains higher than it should be, with six cases of congenital syphilis reported in 2022."
Eliminating congenital syphilis is one of the key aims of Manatū Hauora's Syphilis Action Plan which is part of the wider Sexually Transmitted and Blood Bourne Infections Strategy published earlier this month.
The ESR is working alongside Te Whatu Ora and Te Aka Whai Ora to create better sexual health testing and treatment for syphilis.
