Covid 19: Delta rates holding steady amid Omicron wave

Amid a fast-widening Omicron outbreak, rates of Delta are holding steady – prompting concerns the nastier variant could keep causing hospitalisations here.

Around the world, dominant Omicron has effectively squashed Delta: in England, it took just a month to push Delta down from 98 per cent of recorded cases to just 4 per cent of them.

But experts have remained worried that Omicron’s predecessor could linger strongly enough to have an out-sized impact in our hospitals.

As of last month, Delta cases still made up around a third of those in New South Wales intensive care units – yet just a small portion of those found in the community.

While researchers are still learning about what long-term problems Omicron infections might cause, successive studies have backed early predictions that a given case was typically less severe.

One pre-print study out of the Imperial College London suggested that, compared with Delta, Omicron cases carried an average 15 to 20 per cent lower risk of any hospitalisation – and a 40 to 45 per cent lower risk of actually being admitted.

Another US study that compared Omicron’s surge with Delta’s found the risk of Omicron patients needing to go to the emergency department fell from 15 per cent with Delta to 5 per cent with Omicron, while the risk of being hospitalised dropped from 4 to 2 per cent.

Of all Covid-19 cases sequenced in New Zealand over the past two weeks, 5 to 7 per cent of them were Delta, which appeared to be “holding steady”, ESR’s Dr Joep de Ligt said.

These cases were linked all the way back to our first Delta incursion last August.

“While there are some regions where Delta is more active, it is spread across the motu,” he said.

“For example, a virus clade – a New Zealand-specific version of Delta – that was first identified spreading at North Auckland social events has now made its way to the capital.”

Noting Delta’s higher risk of severe disease, de Ligt urged people to get boosted and wear masks.

He said New Zealand would be wise to “keep a wary eye out” and maintain our best efforts to curb the variant.

Otago University virologist Dr Jemma Geoghegan said contact tracing services should give any detected Delta cases priority – although that wouldn’t be so easy with Omicron spreading our resources more thinly.

She wasn’t surprised Delta hadn’t been wiped out completely in New Zealand, given a sustained level 4 lockdown wasn’t enough to eliminate it, and undetected chains of transmission had been quietly persisting.

“It’s what we’re seeing in other places, where, although Omicron is definitely the dominant variant, others, especially Delta, are continuing in the background.”

With New Zealand having had little prior exposure to either variant, she said it was difficult to say just how Omicron and Delta might compete in the community.

Because being infected with one didn’t stop people from contracting the other, it was all the more important that Kiwis ensured they were boosted.

University of Melbourne-based Kiwi epidemiologist Professor Tony Blakely agreed New Zealand had to try all it could to dampen down Delta.

“You’ve got to take it seriously. That means testing and targeting Delta patients first.”

Blakely said while Delta had endured amid Australian Omicron outbreaks, there was some hospital data now to suggest that its presence in ICU cases had fallen away significantly.

In New Zealand, the Ministry of Health doesn’t publish variant-specific hospitalisation data.

Yesterday there was a record 1573 new community cases in New Zealand – 1140 of them in Auckland.

The remaining community cases were in Northland (31), Waikato (143), Bay of Plenty (29), Lakes (35), Hawke’s Bay (2), MidCentral (3), Whanganui (11), Taranaki (8), Tairāwhiti (8), Wairarapa (30), Capital and Coast (20), Hutt Valley (22), Nelson Marlborough (49), Canterbury (7), and the Southern region (35), the Ministry of Health said in a statement.

Sixty-three people were in hospital with Covid-19 – none in intensive care. They are in hospitals in Auckland, Rotorua, Tauranga, Waikato, Wellington and Tairāwhiti.

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