In late stages of infection patients can develop blindness, paralysis, numbness and dementia. The disease can eventually damage internal organs and can result in death.
A pregnant woman with syphilis can pass the infection on to her unborn baby which may lead to a low birth weight, early birth or stillbirth.
The cure for syphilis is a shot of antibiotics, and is easily detected by a blood test.
However, treatment will not undo any damage the infection has previously caused so, it is vital for patients to seek advice as soon as the symptoms appear.
Syphilis cases have been increasing in New Zealand since 2013, particularly in men who have male sexual contacts. This is particularly concerning for health officials because untreated syphilis increases the chance of catching an HIV infection.
It is also widely believed the embarrassment associated with STIs is a barrier for people seeking help, and is the leading reason for syphilis going undiagnosed.
"Unlike measles, details of cases will not be reported because of the stigma associated with STIs," Dr Robertson said.
Authorities also found many people didn't want the tests on their medical records.
The Midcentral District Health Board said testing should be offered as part of routine STI checks, and to individuals presenting with symptoms. It is also recommended males who have sexual contact with other males be offered annual testing.
Syphilis symptoms can be hard to detect as they often mimic other disorders. Signs of primary infection include an ulcer in the genital area, mouth or anus. This is often painless and not easily noticed.
Symptoms of secondary syphilis occur in 25 per cent of patients, four to 10 weeks after contraction. These include a rash, typically involving hands and feet, hair loss, fatigue, abnormal liver function and nephritis.
