A leading epidemiologist says New Zealand could be facing "an explosion" of COVID-19 cases if the recent traveller from Sydney had the Delta strain of the virus.
Professor Michael Baker told The AM Show on Wednesday the situation is "challenging".
A traveller from Sydney arrived in Wellington in the early hours of Saturday morning, before visiting a number of tourist attractions - including an art exhibition at Te Papa and a busy bar.
Everyone on the flights, and anyone who was at Te Papa or Jack Hackett's Irish Pub is considered a close contact and should isolate immediately.
Baker says the case presents a difficult situation for health authorities.
"A lot of challenges here at the moment, and a big factor is we're dealing with the Delta variant."
The latest case has not been confirmed to have the Delta variant - although it has been spreading in Sydney and Melbourne.
Baker says the variant is "transmitted the same way [as normal COVID-19], it's just much better at it".
"It's roughly twice as infectious, so in a short period of time it will infect more people in indoor environments and if it causes an outbreak it could be a lot more explosive."
He says indoor environments - like a crowded bar, or art exhibition - create "high risk" situations.
The current locations of interest in Wellington are: Qantas Flight QF163 Sydney to Wellington, Rydges Hotel, Unichem Wellington Central Pharmacy, Te Papa Tongarewa - general, Te Papa Tongarewa - Exhibition Surrealist Art: Masterpieces from Museum Boijmans Van Beuningen, Jack Hackett's Bar.
