As Australia transitions into the colder months, COVID-19 is back in the spotlight due to the emergence of a new variant known as NB.1.8.1. The World Health Organization (WHO) has classified NB.1.8.1 as a “variant under monitoring” due to its increasing prevalence and distinct characteristics compared to previous strains.
Current data indicates that while tracking COVID-19 infections has become more challenging due to decreased testing and reporting, case numbers in Australia were on the rise by late May 2025. Genomic sequencing reveals that NB.1.8.1 is circulating within the country, with its prevalence varying by state—ranging from less than 10% in South Australia to over 40% in Victoria. Moreover, wastewater surveillance in Western Australia has confirmed NB.1.8.1 as the dominant variant in samples collected from Perth.
Internationally, NB.1.8.1 has also shown significant growth, comprising roughly 10.7% of all submitted sequences by late April 2025, marking an increase from just 2.5% four weeks prior. This variant is particularly prominent in Asia, where it was the dominant strain in regions like Hong Kong and China at the end of April.
The WHO reports that NB.1.8.1 was first identified in samples collected in January 2025. As a sublineage of the Omicron variant, it derives from the recombinant XDV lineage. The variant carries several mutations in its spike protein, which are of particular interest in understanding its potential impact on transmissibility and vaccine effectiveness.
Research indicates that NB.1.8.1 may have a stronger binding affinity to the human ACE2 receptor than several earlier variants, potentially allowing it to infect cells more effectively. Additionally, studies suggest that antibodies from vaccinated or previously infected individuals may neutralize NB.1.8.1 about 1.5 times less effectively than against other recent variants, indicating a higher likelihood of transmission.
Common symptoms associated with NB.1.8.1 appear to align closely with those of other Omicron subvariants, including sore throat, fatigue, fever, mild cough, muscle aches, and nasal congestion. Importantly, the WHO has not found evidence suggesting that NB.1.8.1 causes more severe disease than earlier variants.
Looking ahead to the winter respiratory season, public health responses will focus on ongoing monitoring, genomic sequencing, and encouraging vaccinations. Despite a modest reduction in neutralizing antibody levels against NB.1.8.1, the WHO reassures that current COVID vaccines are expected to provide protection against severe disease caused by this variant. The most recent booster shot in Australia specifically targets JN.1, from which NB.1.8.1 is descended, suggesting that it will likely still offer effective protection.
As winter approaches and with the new variant spreading, now may be an opportune time for eligible individuals to consider getting a COVID booster, especially for those who are medically vulnerable, as the virus can still pose significant health risks.
This timely evolution in the COVID landscape underscores the importance of remaining vigilant and proactive in public health measures, ensuring community protection during the challenging winter months ahead.