Two new Covid-19 variants have crept into Aotearoa, and although they have not overtaken the current dominant strain, experts are keeping a close eye on their evolution.

The XBB variant has been recorded in New Zealand twice, and BQ.1.1 has been detected in the wastewater in several regions since it was first identified last week.

Western Auckland, Rotorua and Porirua have all had BQ.1.1 in the wastewater but no XBB has been detected in samples yet.

XBB, dubbed the “Nightmare variant” in Singapore, where it has been credited with a sharp increase in infection, is a recombinant variant – meaning two different viruses have infected one person and then spliced together to create a third.

The Washington Post reports that XBB appears to be the best at evading immunity, and researchers in China have found that XBB can elude the protective antibodies generated by a breakthrough BA.5 infection, raising concern that booster vaccines engineered to target the BA.4 and BA.5 versions of Omicron may be quickly outpaced.

According to initial research, BQ.1.1 has a growth advantage relative to BA.5, the dominant variant currently circulating in New Zealand.

“At this stage, there is no evidence that BQ.1.1 is driving an increase in cases but Manatū Hauora - the Ministry of Health, and Te Whatu Ora – Health New Zealand, alongside ESR, are closely monitoring the development of Covid-19 subvariants overseas and in New Zealand, including BQ.1.1.

The Ministry of Health says it is watching the new variants closely based on overseas trends, but BA 5 remains dominant.

Auckland University computational biologist David Welch told NZME there is “no evidence” that XBB is more virulent – meaning it does not appear to cause more serious illness – despite it driving a spike of cases in Singapore.

“We haven’t seen it take off here, although we have detected it.”

He said despite it not overtaking BA 5, it is still “certainly a risk”.

“We’re watching the levels of those variants closely, and we are seeing a slight increase in cases but that’s not due to these variants.”

Welch added that watching what’s happening overseas is no longer as useful as it once was when it comes to predicting Covid-19 surges.

“Countries have different immune profiles these days - they’ve had different waves at different times, different immunity and vaccination and that all adds together to make the world a more complex place.”

He says at this stage there is no reason for the Government to revisit the Covid-19 protection framework – but if cases increased dramatically, it would be a good idea to reimplement masking in crowded areas such as public transport.

“As of right now, no, there’s no need for government regulations - there’s no sign cases are increasing rapidly or that these variants are going to be a real game changer.”