UPDATED: 8.17PM: Investigations are underway into a possible case of the Zika virus being transmitted sexually in New Zealand.

The Ministry of health said a man fell ill after visiting a country where Zika is currently being actively transmitted, and has since tested positive for the virus.

Minstry of Health spokesman Dr Don Mackie said the man's female partner who has not been in a Zika-affected country has also tested positive.

He said both have now fully recovered and suffered only mild symptoms.

"We are looking at a couple of possibilities. The first one is whether the virus was transmitted through unprotected sex. The other one is whether she was bitten by an infected mosquito that perhaps came into the country in her partner's luggage."

Dr Mackie said surveillance of a property is being carried out to check for exotic mosquitos, but none have been found yet.

Auckland University infectious diseases expert Dr Siouxsie Wiles said an infected mosquito in luggage was improbable and sexual transmission of the disease was more likely.

"There are now a handful of cases documenting possible sexual transmission of the virus. They have all been cases of transmission from men to women; so far there have been no cases of transmission from women to men.

"There has also been a case of a man who didn't transmit the Zika virus to his partner but the virus was detected in his semen."

Dr Wiles said sexual transmission of the virus was not the main route of infection.

"It is still quite rare," she said.

"It is important to note that in New Zealand we don't see the kind of sustained spread or transmission as is happening in countries like Brazil. We don't have the mosquitoes that carry the virus here in New Zealand."

Health authorities advise men travelling from an infected country who fall ill to either abstain from having sex or use a condom.

Dr Wiles said the "advice on how long you should wear a condom or abstain from sex for varies,"

"The [World Health Organisation] says four weeks, but the UK is saying up to six months. The reason for this is because at this stage they have no idea of exactly how long a man with Zika infection is likely to have the virus in his semen."

There are only eight reports of Zika being sexually transmitted worldwide.