New Zealand looks on the cusp of another Covid-19 wave similar in size to our last two, a modeller says – but this time, it’s hitting in the thick of sick season.

Six months on from last year’s Christmas wave, Professor Michael Plank says there’d been a “sharp” increase in indicators toward another bump.

That included a jump in hospital admissions last week – from 152 cases in the previous week to 242 – along with a near doubling in reported cases, from 3922 to 6146.

Michael, of Covid-19 Modelling Aotearoa, says genomic sampling also pointed to the local rise of a new group of Omicron strains called FLiRT variants.

It's a public covid report week, and since @RhysTWhite has gone off to play in the UK I better present the highlights: https://t.co/He3IWs6XmY .

We have added a few JN.1 subvariants to our set of tracked variants for all plots: pic.twitter.com/Vdc2HdrNdg

— David Winter (@TheAtavism) May 17, 2024

The strains descended from the long-dominant JN.1 subvariant and packed genetic machinery linked with higher spread – but there was not yet evidence to suggest they made people sicker than their Omicron predecessors.

“So, I think these things are coming together to indicate we’re possibly heading into a new wave at the moment.”

As for how large that wave would be, Michael expected something of similar scale to recent ones.

The most recent wave, which hit just ahead of the summer holidays, pushed weekly hospitalisations to more than 350 – slightly higher than the peak of the preceding “mini-wave” in April last year.

“We’re in a cycle now where, when we get a wave, a significant number of people will get infected and develop some immunity, but over time, that population-level immunity decreases due to waning and the arrival of new variants,” he says.

“Eventually, we reach a point where that immunity level has dropped low enough that the virus can start to increase - and the cycle begins again.”

Quite a jump in Covid hospitalisations to 242 from 152 last week. Plus flu season is just beginning.
Reminder you can book Covid & flu vaccines at https://t.co/rZxjgPfv48
Covid booster free for all over 30s
Flu jab available for all over 6 mo, free for 65+ & other risk groups

— Michael Plank (@MichaelPlankNZ) May 20, 2024

This time, he says it was concerning that the wave was taking off as the winter flu season begins for already-stretched hospitals – something likely to mean delayed operations for some patients.

“It’s tricky to predict exactly what the flu season is going to look like, but in June, we could be looking at quite high levels of flu, combined with high levels of Covid – and that will certainly put pressure on hospitals.”

Besides taking usual health precautions, Michael says the best thing people could do to ease that strain was to get vaccinations for both viruses.

“Now’s a really good time to be getting those to reduce the likelihood of getting sick with either Covid or flu during the winter.”

Jamie Morton is a specialist in science and environmental reporting. He joined the Herald in 2011 and writes about everything from conservation and climate change to natural hazards and new technology.