New Covid Variant PJ.2.1 Spreads in US as Health Officials Step Up Watch

A new Covid variant, PJ.2.1, is spreading across the United States after first being detected in Canada in May, researchers and health officials say. The lineage has now been found in several US states, and genomic surveillance shows its share of sequenced cases rising sharply in Ontario.

There is no evidence so far that PJ.2.1 causes more severe illness than other variants now circulating. But its symptoms closely resemble those of a cold or flu, which means testing is the only reliable way to tell it apart from other seasonal respiratory infections.

First found in Canada in May

The earliest confirmed sample of PJ.2.1 was collected in Ontario on 2 May 2026, according to a study by virologist Markus Hoffmann and colleagues published in the Journal of Infection on 24 October 2026.

PJ.2.1 descends from MC.10.1.7, a branch of the JN.1 lineage within the Omicron family. Researchers have described it as a “saltation variant” because it carries an unusually large number of mutations, many of them in the spike protein the virus uses to enter human cells.

The World Health Organization has not designated PJ.2.1 a variant of concern, a variant of interest, or a variant under monitoring. In a call on 27 October, the WHO asked countries to share immunity data on newly emerged variants, including PJ.2.1, ahead of its December review of Covid-19 vaccine composition.

How far it has spread in the US

The first US detection came in New York City on 30 June 2026. Since then the variant has been identified in California, Arizona, New Jersey, Virginia, North Carolina, Missouri, Oklahoma, Colorado and Florida.

It has also been reported in Spain, France, Israel, Singapore, Australia and New Zealand.

The clearest picture of its growth comes from Ontario, where genomic surveillance tracked a steep rise. PJ.2.1 accounted for 1.1 percent of sequenced cases between 28 June and 25 July, then 3.5 percent in the following four weeks, 16.9 percent from 23 August to 19 September, and 25.2 percent from 20 September to 17 October. In that latest window, 132 of 523 sequenced samples were PJ.2.1, making it the most frequently detected lineage in the province.

Health officials caution that those figures reflect only cases that were sequenced, not all infections, so they show the variant’s share among tested samples rather than its true prevalence.

What the science says so far

Laboratory work in the Hoffmann study found that PJ.2.1 binds more strongly to ACE2, the receptor the virus uses to enter cells. In neutralisation tests, antibodies were about 1.8-fold less effective against PJ.2.1 than against LP.8.1, a recently circulating lineage. Even so, serum from people immunised with an adapted LP.8.1 vaccine still neutralised the new variant in the laboratory.

The study also found PJ.2.1 more frequently in older age groups, particularly people aged 70 and over. Researchers stressed that this does not prove the variant targets older people or causes worse disease in them.

On the question that matters most, the evidence is reassuring for now. Health and Me reported that the WHO said symptoms of the variant may resemble those of a common cold or flu. OnlyMyHealth reported that the WHO has warned the variant’s symptoms can be difficult to distinguish from other respiratory illnesses. Neither the WHO nor the published research has found evidence that PJ.2.1 causes more hospitalisations or deaths than earlier variants, and laboratory results alone cannot show how efficiently it spreads between people.

Why testing matters

Because PJ.2.1 looks, symptom for symptom, like a cold or flu, health officials say people with respiratory symptoms should test rather than assume which virus they have. That matters most for older people and those with underlying conditions, who face the highest risk from any Covid infection. Without sequencing, a new lineage can also spread for months before anyone notices it is gaining ground.

What officials are watching next

The WHO continues to track PJ.2.1 and other emerging lineages, and its December vaccine-composition review will weigh immunity data on the variant. The variant is arriving as US health agencies track several outbreaks at once. Florida is also dealing with a dengue outbreak, while health agencies continue to monitor the Ebola outbreak in Congo. Against that backdrop, PJ.2.1 is one more lineage to watch, not a new emergency.

Frequently asked questions

What is the PJ.2.1 variant?

It is a lineage of SARS-CoV-2, the virus that causes Covid-19, from the JN.1 lineage of the Omicron family, first identified in Ontario, Canada, on 2 May 2026.

Is PJ.2.1 more dangerous than other variants?

There is currently no evidence that it causes more severe illness, hospitalisation or death than other circulating variants. Its symptoms resemble a cold or flu.

Where has PJ.2.1 been found in the United States?

It was first detected in New York City on 30 June 2026 and has since been reported in California, Arizona, New Jersey, Virginia, North Carolina, Missouri, Oklahoma, Colorado and Florida.