The mantra first used by public health experts to help stomp on the spread of COVID-19 is now being applied to sexually transmissible infections.

Advocates and researchers believe the unique set of societal conditions produced by the lockdown gives an opportunity to break the chain of transmission - one that cannot be missed.

"If we have broken the chain of COVID transmission through physical distancing then it follows that we may well have broken the chain of HIV and STI transmission," Jason Myers, chief executive of the New Zealand AIDS Foundation told AAP.

New Zealanders were housebound, except for essential tasks and essential workers, during a 51-day lockdown that ended earlier this month.

The country's eradication efforts have all but eliminated the disease in New Zealand. There are just eight active cases across the country, with no Kiwis requiring hospital-level care.

That's prompted Jacinda Ardern's government to ease gathering restrictions again from Friday.

Gatherings of up to 100 people are now allowed, though physical distancing between strangers still a part of the regime.

"What needs to happen now is before people re-enter the realm of sex with casual partners, they need a test," Mr Myers said.

"We know there are a number of New Zealanders living with undiagnosed HIV infection.

If we can find those individuals through testing, diagnose them with HIV and link them to care and treat them we will have broken the chain.

"So we need to test."

New Zealand has a similar STI profile to Australia, with epidemic-like levels of syphilis within the community.

This week, the government-backed AIDS Epidemiology Group at the University of Otago, released data that showed an increased rate of growth of Kiwis living with HIV.

In 2018, 185 new cases were identified. In 2019, that figure grew to 212.

Group leader Sue McAllister said she was "encouraged" by a decrease in the number of cases that were first diagnosed in New Zealand.

A small increase in cases first diagnosed overseas may be attributable to Kiwis returning home, international students or migrant workers, but Dr McAllister said it was important to note that New Zealanders receiving treatment for HIV posed no risk to the population.

Two-thirds of local transmissions occurred between men who have sex with men and 17 per cent occurred through heterosexual sex.

Dr McAllister said improved prevention methods of condom use, early testing and treatment, and access to pre-exposure prophylaxis helped with the local decline.

Australian Associated Press