WELLINGTON, Sept. 21 (Xinhua) -- Experts call for caution as New Zealand has detected the highly mutated COVID-19 variant BA.2.86, known as "Pirola," in wastewater samples taken earlier this month.

"Pirola," the Omicron subvariant detected by the New Zealand Institute of Environmental Science and Research, has been declared a "variant under monitoring" by the World Health Organization, and has been gradually spreading around the world since it was first discovered in Denmark and Israel in late July.

There are currently no indications that it is substantially more severe or infectious than other subvariants circulating in the communities, the Ministry of Health said in a statement.

The variant stands out because it has a much larger number of mutations than other variants that have taken off over the last year or so, Prof. Michael Plank of the University of Canterbury, New Zealand's mathematical modeler of COVID-19, said on Thursday.

"The fact that cases of BA.2.86 popped up around the same time in countries with good genomic surveillance suggested we might just be seeing the tip of a rapidly growing iceberg," Plank said.

That led to concerns that the variant could bypass immunity from vaccination and previous infections and spread explosively like Omicron did when it first burst onto the scene in late 2021, he said.

However, since then, although BA.2.86 has managed to get a foothold in lots of places, it hasn't shown a major growth advantage, Plank said, stressing the importance of maintaining good surveillance to prevent it from spreading faster.

Michael Baker, professor at the University of Otago, Wellington, said it shows how the COVID-19 virus is still capable of "big evolutionary jumps," which is a further reminder that the pandemic remains unpredictable and is certainly not over. ■