Zika infections have tripled in New Zealand in the past week. 31 cases have now been confirmed this year, all of them were infected overseas, but so much about the virus is still unknown.
So far this year there have been 31 confirmed cases and all of them were infected overseas. 17 came from Tonga, 13 came from Samoa and one was from American Samoa.
But it's not new to New Zealand; there were 57 reported cases in 2014 and nine (provisional) in 2015.
The virus was originally identified in Uganda in 1947. Some suggest the recent outbreak may be due to virus mutation while others say it may have reached a new area where there is low immunity, because people haven't been exposed to it before.
It can cause a fever, rash, joint pain and conjunctivitis - but it's thought four out of five do not develop symptoms. It's unclear whether those who are asymptomatic are infectious.
The outbreak has prompted the World Health Organisation (WHO) to declare an international public health emergency, due to thousands of suspected cases of microcephaly in Brazil. But although the link is strongly suspected, it has not yet been scientifically proven.
The overwhelming majority of cases have been spread by mosquito bites, but sexual transmission has been implicated in a couple of infections, so people are warned to take precautions for up to a month after travelling to affected countries.
The Zika virus is spread by the Aedes Aegypti mosquito, which does not exist in New Zealand. But experts say they can't rule out that Zika could be spread by other mosquitoes too.
The New Zealand Blood Service requires people to defer donating for 28 days following departure from affected countries, or 28 days following complete recovery if they were unwell during or subsequent to the period of travel. These current measures will provide a high level of protection against transmission of Zika virus by transfusion.