Professor Michael Baker says the new NB.1.8.1 is becoming dominant in a number of countries and would "almost certainly" do the same in New Zealand. Photo: Supplied to RNZ
A sudden surge in Covid-19 detections - along with the emergence of a new, and what's thought to be more infectious, subvariant - should be a warning to take action, an epidemiologist says.
NB.1.8.1 is now the dominant strain in China and Hong Kong. ABC News reports it is also driving up infections in Australia.
Here, the latest available ESR wastewater testing to 11 May shows the sub-variant making up 21.6 percent of readings.
Epidemiologist Michael Baker said it comes as overall Covid-19 detections surge.
"We've had a long period when Covid levels have been relatively low in New Zealand. It's about 11 months since our last big wave, the sixth wave, in June last year."
Baker said there were numerous surveillance systems giving an idea of how the virus was spreading, and most were not showing changes. However that was not the case for wastewater testing.
"There's quite a striking spike in the wastewater samples and the positivity detected there. And numbers are really shooting up across the country, so for the first time in around 11 months we're seeing what looks like the beginning of a wave."
Wastewater testing reveals a spike in Covid-19 cases nationally. Photo: Supplied / ESR
Baker cautioned it was too early to see a clear picture and further results over the next week or two would help.
"But I think it is a strong warning that we should be taking more action around Covid-19 in various ways."
Baker said NB.1.8.1 was becoming dominant in a number of countries and it would "almost certainly" do the same in New Zealand.
"We see many new subvariants and most of the time they're not translating at the moment into a rise in cases.
"But that's why this one is different - we are seeing that early increase, but we're not seeing it in all the surveillance systems yet, so we just need to keep watching.
"I think the message is very clear that we're moving into winter, we have got this rise in cases - and if anyone has been putting off getting their Covid-19 booster, now would be a good time to get it."
Baker said health authorities should also be taking additional precautions in hospitals, residential care facilities in particular.
He said the existing vaccine gave added protection against the new subvariant, which descended from a variant the vaccine is based on.
"I think it's all adding up to a picture of the need to take precautions against this infection."
Sign up for Ngā Pitopito Kōrero, a daily newsletter curated by our editors and delivered straight to your inbox every weekday.
