Two cases of LGV, or Lymphogranuloma venereum, have been recorded here in the past year, but health officials say it is possible others may be unknowingly infected with the disease, as it is not routinely tested for.
It is caused by specific strains of chlamydia and is often marked with painful, bloody rectal infection and genital ulcers. The symptoms are severe and can lead to long-term complications and enhance the transmission of HIV.
Recent outbreaks have been documented in the US and Europe but until now there have been no confirmed cases in New Zealand.
Both the documented cases occurred in the North Island - in Auckland and Palmerston North - and health officials believe they were connected.
"These cases were only noticed because the clinicians involved were alert to the possibility and decided to investigate further," said Auckland Sexual Health lead clinician Dr Nikki Perkins, who is concerned by the disease's emergence here.
"I don't think people should be panicking about it . . . but it is an emerging trend that we are keeping an eye on and wanting to identify further."
Perkins said assessing the extent of the disease's spread was difficult as only one laboratory in the country could currently test for it and it was not picked up during routine testing for sexually transmitted infections.
"There is a test for it [LGV] in one of the Wellington laboratories, but as yet there is no test for it in Auckland although we have been working with LabPlus and they have developed a test for it specifically, which we hope to be using quite soon."
Christchurch Sexual Health clincial director Dr Edward Coughlan said although no cases of LGV had been reported in the South Island he expected New Zealand would mirror worldwide trends with an increase in cases here.
The disease can be treated with a long course of antibiotics.