Monkeypox is now being tested for in wastewater, as part of a new trial by ESR.
There are 32 cases of the virus known to be in the country.
Testing wastewater for the virus was new, even internationally.
An ESR spokesperson said the trial would help it better understand how effective the testing was at identifying the virus' DNA - and to understand whether there were any limitations.
Samples were being taken from a "limited number" of sites in main centres near where people were known to have monkeypox, but ESR would not say where.
That was because so few people had the virus it wanted to make sure it was protecting their privacy.
The results would not be made public during the trial phase
Of the current known cases, 23 were caught locally and nine acquired overseas, with case numbers updated ever Thursday.
The Ministry of Health said the risk of the virus spreading widely in New Zealand was low because it was not very contagious.
It was mainly transmitted through close physical contact with someone who had the virus, direct contact with their rashes, or through bedding, clothing or towels they had used.
It could also be passed through breathing in droplets that had been exhaled but it normally required prolonged contact and for people to be very close, the Ministry advice said.
RNZ
