Why scientists call PJ.2.1 a ‘jump’ variant: The COVID strain that arrived with dozens of mutations at once and spreads by gripping your cells more tightly

A new variant of concern is being identified and is the subject of scientific interest following its detection in Canada in May 2026 and subsequent spread to a number of other countries. Known as PJ.2.1 it has over 25 spike protein mutations and has demonstrated unusually strong binding to human cells in the lab. Scientists are looking at whether these changes might help it to spread further (though there is currently no evidence that it causes any more severe illness).

Why is PJ.2.1 being called a 'jump' variant?

PJ.2.1 is in the SARS-CoV-2 family and is a descendant of the MC.10.1 lineage, which goes back to JN.1. It's described as a saltation variant, as it arose with a large number of mutations rather than having evolved through a series of smaller mutations.


The first sample that was ever documented was collected in Ontario, Canada, on May 2nd 2026. A paper in the Journal of Infection published on 24th October looked at its rather odd genetic characteristics.

Researchers have identified over 25 changes in its spike protein (the part of the virus that enables it to bind to human cells).

What's so unusual about its ability to bind to human cells?

The study found that PJ.2.1 bound very strongly to the ACE2 receptor. ACE2 is the receptor that SARS-CoV-2 uses to get into human cells. In the lab comparisons, PJ.2.1 bound better than a number of the current variants (NB.1.8.1, XFG and BA.3.2.2).

However, stronger receptor binding doesn't necessarily equate to more severe disease or faster transmission between people. Researchers also found that PJ.2.1 didn't show much immune escape. Its sensitivity to antibodies was as good as, or better than, that seen with the other variants.

Where is PJ.2.1 spreading and what are its symptoms?

PJ.2.1 was also detected in the US, Spain, France, Israel, Singapore, Australia and New Zealand after it had been seen in Canada. Public Health Ontario reported that it made up 25.2% of the samples they had sequenced between 20 September and 17 October, up from 16.9% in the prior four-week period.

There is no confirmed symptom pattern specific to PJ.2.1. The possible symptoms are fever, cough, sore throat, runny or blocked nose, headache, body aches and fatigue. Some people may also have digestive issues, breathing difficulties and/or changes to their sense of taste and smell. As per the WHO, the symptoms can be very similar to the flu and other respiratory infections.

Is PJ.2.1 a serious threat?

As of 8th November, there wasn't enough evidence to show that PJ.2.1 causes any more hospitalisations, any more severe disease or any more deaths than the other variants. Older people, pregnant people, those with weakened immune systems and people with certain underlying medical conditions are at greater risk of developing severe COVID-19.

The WHO are still monitoring the variant. The researchers feel that its unusual receptor binding is such that continued genomic and epidemiological surveillance is important. The information is taken from AgroReview and Open Magazine.