The native bird found to be infected with the deadly H5 bird flu in Wairarapa was actually the country’s first case of the virus, not the second.

The kāhu, or swamp harrier, was discovered in Carterton and taken to Massey University’s Wildbase clinic on July 9 — the day before an infected brown skua was found on Wellington’s Petone Beach.

Wildlife veterinarian professor Brett Gartrell said the harrier was “stuck in a fence” and admitted to the animal hospital with suspected head trauma.

“We weren’t even thinking about highly pathogenic avian influenza at the time,” he said.

The bird deteriorated overnight and was put down the next morning. It was tested for bird flu as part of routine surveillance, he said.

“It was a surprise to all of us when it came back positive.”

Gartrell said it wasn’t surprising to find the virus in a bird of prey.

The harrier most likely contracted the virus after feasting on a sick seabird blown ashore in July’s stormy weather, he said.

It followed an established pattern of infection in scavenging or carnivorous bird populations overseas, he said.

“In the [United Kingdom] peregrine falcons have been hit really hard by this… virus because they pick up sick and dying birds and eat them and get infected themselves.

“So, it does look like birds of prey are going to be really hit by this.”

Gartrell said the kārearea, New Zealand’s only falcon, was the biggest cause for concern due to its low population numbers — between 5000 and 8000, according to the Department of Conservation.

There are still only two confirmed cases of bird flu in NZ. It has been almost two weeks since the last confirmed case, but Gartrell warned that wouldn’t last.

“When these infections first come in they’re often very slow to get established but they build in intensity as more and more birds get infected.

“We’ve been given a bit of a lull … but I think it still is definitely coming.”

Gartrell said bird-to-bird transmission was unlikely at this stage, but the same couldn’t be said for Australia.

“Most recently, they’re seeing a cluster of mortality in a group of terns, which is a coastal species that flocks close together.”

As of Tuesday, Australia had 27 confirmed cases of H5 bird flu in wild seabirds, with South Australian authorities warning local spread was “very likely”.

Ministry for Primary Industries (MPI) chief veterinary officer Mary van Andel confirmed tests from the harrier were delivered to MPI’s laboratory on July 14.

She said that testing involved two rounds — the first to identify avian influenza and the second to confirm whether it was a high-pathogen or low-pathogen strain.

Test results confirmed it was highly pathogenic on July 17.

Van Andel said there had been a strong response from the public, with 1267 notifications about sick or dead birds as of Wednesday morning.

Given the location of the two confirmed detections, a large number of those reports were from the Wellington region, she said.