The X-B-B.1.5 strain has been called the most transmissible Omicron subvariant yet by the World Health Organisation.
Its growth advantage refers to the strain's highly immune-evasive nature and its ability to bind more tightly to human cells, making it more infectious.
This infectiousness is also tied to the reduced ability of current vaccines to stop the spread of infection.
In November, the WHO drew attention to early evidence pointing at a "higher reinfection risk" from X-B-B.1.5, as compared to other circulating Omicron sublineages.
Most data on the new X-B-B strain has come from the United Kingdom, Denmark, and the United States of America.
The strain accounted for 28 per cent of new COVID-19 cases in the U-S last week, according to health officials.
On the other side of the world, China has seen recent widespread infections with the new X-B-B variant detected amongst a wave of new patients.
Experts such as Antoine Flahault, from Geneva's Institute of Global Health, believe the rapid spread through their 1.4 billion population "creates conditions prone to emerging variants."
However, Imperial College London's Professor Barclay says it shouldn't be assumed that China will be the breeding ground for new strains.
While data from New South Wales health indicate that there have only been a "small number of detections" in Australia so far, authorities recommend getting a booster shot if you haven't already, and a fourth dose of vaccine if you're a vulnerable person.
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