What we know so far about the new Covid variant NB.1.8.1.

As we enter the colder months in Australia, Covid-19 is making headlines again, this time due to the emergence of a new variant: NB.1.8.1.

Last week, the World Health Organization designated NB.1.8.1 as a “variant under monitoring”, owing to its growing global spread and some notable characteristics which could set it apart from earlier variants.

So what do you need to know about this new variant?

The current Covid situation

More than five years since Covid was initially declared a pandemic, we’re still experiencing regular waves of infections.

It’s more difficult to track the occurrence of the virus nowadays, as fewer people are testing and reporting infections. But available data suggests in late May 2025, case numbers in Australia were ticking upwards.

Genomic sequencing has confirmed NB.1.8.1 is among the circulating strains in Australia, and generally increasing. Of cases sequenced up to May 6 across Australia, NB.1.8.1 ranged from less than 10% in South Australia to more than 40% in Victoria.

Wastewater surveillance in Western Australia has determined NB.1.8.1 is now the dominant variant in wastewater samples collected in Perth.

Internationally NB.1.8.1 is also growing. By late April 2025, it comprised roughly 10.7% of all submitted sequences – up from just 2.5% four weeks prior. While the absolute number of cases sequenced was still modest, this consistent upward trend has prompted closer monitoring by international public health agencies.

NB.1.8.1 has been spreading particularly in Asia – it was...

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