Two of the new cases are in a Wellington family who recently returned from the United States, and the third is a Dunedin man who had recently travelled to Germany.

"All these cases are associated with overseas travel," Dr Bloomfield says.

The two new Wellington cases are a man who is in his 30s and his father who is in his 70s. The younger man became unwell on the flight and his father felt ill the following day.

Neither require hospital care and they are both recovering at home.

They travelled on American Airlines flight AA83 from Los Angeles to Auckland, arriving on March 14. They sat in seats 4A and 10H. They then flew to Wellington on flight NZ419 that same day and their seat numbers were 1B and 1C.

The Public Health Unit and Healthline have been contact tracing passengers who were sitting near them on both flights.

Dr Bloomfield says if you were sitting near these seats on either flight but you haven't been contacted, you can call Healthline on 0800 358 5453. There is no need for casual contacts to call Healthline, only those who were in close contact with either passenger.