The Auckland District Health Board is warning people of the increased danger of the transmission syphilis amid an outbreak of the disease.
The Auckland District Health Board deputy chief medical officer, Dr Richard Sullivan, said there was a concerning pattern emerging as numbers continued to rise, both in the Auckland region and globally.
So far this year, there have been 124 cases of the sexually-transmitted disease reported, an increase on the 120 reported at this time last year.
Regional Public Health Service figures show 78 percent of cases reported in the last year were men.
People who had contracted the disease were predominantly between the ages of 20 and 49.
He said tackling the syphilis outbreak was a "major focus" for the Regional Sexual Health Service (ARSHS) and the Regional Public Health Service (ARPHS), as part of the Ministry of Health's national action plan.
"[The organisations] are working together to jointly respond to the outbreak and improve rates of testing, contact tracing, and notification of syphilis cases," Mr Sullivan said.
ARSHS had increased the number of staff undertaking syphilis contact tracing, he said.
One possible reason for the rising figure may be the increase in contact tracing work that meant more cases were being identified and treated.
"We are focusing on increasing awareness of syphilis amongst health professionals and the public, and are promoting a safe sex culture as a vital component of sustainably addressing the increase in syphilis cases.
"Syphilis is a serious disease that, if left untreated over time, can affect the brain, spinal cord and other organs," he said.
"The infection can also have a serious impact on unborn babies, leading to stillbirth or congenital syphilis, as well as potentially causing abnormalities such as blindness, deafness and meningitis," Mr Sullivan said.
Those wanting to steer clear of syphilis should use protection, have regular STI checks, communicate their diagnosis with sexual partners and limit their number of sexual partners to reduce the chance of contracting it.