Covid 19 Omicron outbreak: Could the Delta variant return to the Bay of Plenty?

The Bay of Plenty District Health Board says Delta was last detected in the Bay on March 2. Photo / Andrew Warner

Omicron has "overwhelmed" Delta but other Covid variants may arrive once the borders open, a public health expert says.

It comes as the Bay of Plenty District Health Board says the most recent case of Delta identified in the Bay was on March 2. It has not been detected since.

Meanwhile, the Ministry of Health reported today one person died with Covid-19 in the board's region. Nationally, the ministry reported 34 Covid-related deaths.

There were 28 patients with Covid-19 in the Bay of Plenty DHB's hospitals.

There were 967 new cases of Covid-19 in the region, which included both PCR tests and RATs. Nationally, there were 17,148 new cases.

University of Waikato professor of public health Ross Lawrenson. Photo / Supplied

University of Waikato professor of public health Ross Lawrenson said it was more likely a new variant would arrive rather than Delta coming back.

"We are worried as the borders open that there may be other variants that come in."

Currently, people were getting either the sub-type of BA.1 or BA.2 Omicron, he said.

"We're assuming that that's overwhelmed Delta.

"We may be wrong - there may be some cases out there of Delta that we just haven't identified.

"Generally, I don't think that's likely because the Delta cases tend to get sicker. And if they're sicker then they will be more likely in hospital and we are testing those in hospital.

"We're not seeing Delta and we're not expecting a resurgence of Delta."

Lawrenson said the most infectious variants became dominant "quite quickly" and the less infectious variants "die out" because they were not being transmitted in the same way.

"Hopefully if there are future variants, they will remain relatively mild or even milder which would be great."

He said the "large numbers" of people getting Omicron would get "some protection" against future variants.

Bay of Plenty District Health Board Covid-19 incident controller Trevor Richardson. Photo / George Novak

Bay of Plenty DHB Covid-19 incident controller Trevor Richardson said the most recent case of Delta identified in the Bay of Plenty was in Tauranga on March 2.

Delta has not been detected in the Bay since, he said.

All positive specimens sent for sequencing since this case have proven to be Omicron, he said.

Richardson confirmed genome sequencing was still occurring to determine whether someone had the Omicron or Delta variant.

"Some providers are asking patients who return a positive result on their RAT to be re-tested with a PCR swab."

The swabs are then sent to a lab for genomic sequencing, he said.

"This process is called 'surveillance testing' and is a prudent way to monitor what types of Covid-19 might be circulating in our communities."

When asked about 'Deltacron', Richardson said at this stage it was "an emergent strain".

"As with every variant, we are closely watching international developments and will be providing public health advice as and when appropriate.

"This variant has been reported from the United Kingdom and other parts of Europe, but so far there have been no cases reported in New Zealand."

Richardson said Covid had the ability to evolve into new variants, similar to the flu and other viruses.

"We've already seen Delta and Omicron arrive in New Zealand, and we can expect to see other new variants come here in future.

"It's important that we continue to monitor new variants as they emerge overseas. Genomic sequencing is a key tool for identifying when such variants arrive in New Zealand."