JN.1 ‘step change’ evolution cause for new Covid concern

Since it was detected in August 2023, the JN.1 variant of Covid has spread widely. It has become dominant in Australia and around the world, driving the biggest Covid wave seen in many jurisdictions for at least the past year.

The World Health Organization (WHO) classified JN.1 as a “variant of interest” in December 2023 and in January strongly stated Covid was a continuing global health threat causing “far too much” preventable disease with worrying potential for long-term health consequences.

JN.1 is significant. First as a pathogen – it’s a surprisingly new-look version of SARS-CoV-2 (the virus that causes Covid) and is rapidly displacing other circulating strains (omicron XBB).

It’s also significant because of what it says about Covid’s evolution. Normally, SARS-CoV-2 variants look quite similar to what was there before, accumulating just a few mutations at a time that give the virus a meaningful advantage over its parent.

However, occasionally, as was the case when omicron (B.1.1.529) arose two years ago, variants emerge seemingly out of the blue that have markedly different characteristics to what was there before. This has significant implications for disease and transmission.

Until now, it wasn’t clear this “step-change” evolution would happen again, especially given the ongoing success of the steadily evolving omicron variants.

JN.1 is so distinct and causing such a wave of new infections that many are wondering whether the WHO will recognize JN.1 as the next variant of concern with its own Greek letter. In any case, with JN.1 we’ve entered a new phase of the pandemic.

Where did JN.1 come from?

The JN.1 (or BA.2.86.1.1) story begins with the emergence of its parent lineage BA.2.86 around mid-2023, which