
The Rise of the New COVID Variant NB.1.8.1: What You Need to Know
2025-05-28
Author: Wei Ling
Australia Faces New COVID Threat as Cold Months Approach
As the chilly season sets in across Australia, COVID-19 is back in the spotlight, this time with the emergence of a new variant: NB.1.8.1.
WHO Flags NB.1.8.1 as a Variant Under Monitoring
Last week, the World Health Organization officially classified NB.1.8.1 as a "variant under monitoring" due to its rapid spread and unique characteristics that differentiate it from earlier strains.
Current COVID Landscape in Australia
It's been over five years since COVID-19 was declared a pandemic, and we still find ourselves facing regular waves of infections. Tracking the virus has become increasingly difficult as fewer individuals are testing and reporting positive results. However, data indicates that toward the end of May 2025, case numbers began to rise again in Australia.
Genomic sequencing has confirmed that NB.1.8.1 is circulating in Australia, with prevalence varying by state—ranging from under 10% in South Australia to over 40% in Victoria. Interestingly, wastewater testing in Western Australia shows that NB.1.8.1 is now the predominant variant detected in Perth.
Global Spread of NB.1.8.1
Internationally, NB.1.8.1 is on the rise as well. By late April 2025, it made up approximately 10.7% of all submitted genomic sequences, a significant increase from just 2.5% four weeks prior. This upward trajectory has led global health authorities to monitor the variant more closely.
The variant is spreading rapidly across Asia, becoming the dominant strain in regions such as Hong Kong and China as of late April.
The Origins of NB.1.8.1
According to the WHO, NB.1.8.1 was first identified in samples collected in January 2025. It is a sublineage of the Omicron variant, specifically derived from the recombinant XDV lineage, where a new variant emerges through the genetic mixing of existing strains.
What the Research Is Uncovering
Like its predecessors, NB.1.8.1 showcases a range of mutations in the spike protein, which plays a critical role in how the virus infects cells. Some notable mutations include T22N, F59S, G184S, A435S, V445H, and T478I.
Initial research indicates that NB.1.8.1 has a stronger binding affinity to human ACE2 receptors compared to other variants, suggesting it may be more efficient at invading human cells. Furthermore, the neutralizing response from antibodies—whether from vaccines or previous infections—was observed to be about 1.5 times lower against NB.1.8.1 than against another recent variant, LP.8.1.1. This raises concerns that individuals infected with this new variant might transmit it more easily.
Symptoms to Watch For
So far, it appears that NB.1.8.1 spreads more easily and may circumvent some immunity provided by prior infections or vaccinations, which aligns with the observed rise in its prevalence. However, the WHO has found no evidence indicating that this variant causes more severe disease than previous strains.
Common symptoms are expected to mirror those of other Omicron subvariants, including sore throat, fatigue, fever, mild cough, muscle aches, and nasal congestion. Gastrointestinal symptoms might also present in some cases.
Vaccine Efficacy Against NB.1.8.1
With winter approaching, NB.1.8.1 has the potential to significantly impact Australia’s respiratory season. Public health measures are focused on closely monitoring the situation, continuing genomic sequencing, and encouraging the uptake of updated COVID-19 boosters.
Despite some reduction in neutralizing antibody levels against NB.1.8.1, the WHO asserts that current vaccines should still be effective in preventing severe disease caused by this variant. The latest booster in Australia is designed to target the JN.1 variant, which is closely related to NB.1.8.1, suggesting it should provide robust protection.
With another variant on the rise, now is a crucial time for those eligible to consider getting an updated COVID-19 booster, especially for those who are more vulnerable to severe illness.