- PJ.2.1 was first detected in Ontario, Canada, on May 2, 2026, and has since been identified in North America, Europe and Asia
- Symptoms can resemble flu and the common cold, making diagnosis based on symptoms alone unreliable
- Laboratory research found increased cell-entry efficiency, but has not established that the variant causes more severe disease in humans
The World Health Organization (WHO) has warned that symptoms associated with the emerging Covid-19 variant PJ.2.1 can resemble those of influenza and the common cold, making it difficult to identify the infection based on symptoms alone.
The organisation said symptoms of Covid-19, influenza and other respiratory infections can overlap, and testing may be necessary when identifying the cause of an illness could influence treatment decisions or public health measures.
PJ.2.1 was first detected in Ontario, Canada, on May 2, 2026. It has subsequently been identified in other Canadian provinces, several US states and countries including Spain, France, Israel, Singapore, Australia and New Zealand.
The WHO is monitoring the variant as researchers investigate its spread and biological characteristics. However, there is currently no evidence that it causes a more severe course of illness than other circulating coronavirus variants.
The variant belongs to the SARS-CoV-2 family of viruses responsible for Covid-19. Its spike protein, which enables the virus to attach to human cells, carries a significant number of mutations.
Is PJ.2.1 the same as the 'American Covid' variant?
PJ.2.1 should not be confused with XFG, the coronavirus lineage referred to in media reports as 'American Covid' or the Stratus variant. Both belong to the SARS-CoV-2 family, but they are distinct lineages.
XFG has been circulating internationally since early 2025 and has attracted attention in the UK following an increase in Covid-19 activity and hospital admissions during autumn 2026. The UK Health Security Agency (UKHSA) has identified XFG as the lineage associated with the 'American Covid' nickname, although the name is not an official scientific designation.
Pharmacy Business previously reported on the increase in hospital admissions associated with the American Covid strain and the NHS advice for people experiencing symptoms to stay at home and avoid contact with others.
Unlike XFG, PJ.2.1 is the emerging lineage examined in the latest Journal of Infection study. There is currently no evidence that it causes more severe illness than other circulating variants. The two lineages should therefore be treated separately when discussing their spread, symptoms and potential health risks.
What are the symptoms of Covid variant PJ.2.1?
There are currently no confirmed symptoms that uniquely distinguish PJ.2.1 from other circulating COVID-19 variants.
Possible symptoms include fever, cough, sore throat, a blocked or runny nose, headache, muscle aches and fatigue. Some people may also experience digestive problems, shortness of breath or changes in their sense of smell and taste.
These symptoms can also occur with seasonal influenza and other respiratory infections, making it difficult to identify the virus responsible without diagnostic testing.
Russian infectious disease specialist and virologist Elena Malinnikova has suggested that severe sore throat and prolonged fatigue after recovery may be associated with PJ.2.1. However, these observations have not been established as distinctive clinical features of the variant.
The WHO has emphasised that symptoms alone cannot reliably determine whether someone has Covid-19, influenza or another respiratory infection. Testing may be appropriate where establishing the cause could affect treatment or public health decisions.
A positive Covid-19 test can confirm a SARS-CoV-2 infection, but it cannot identify the specific variant. Genomic sequencing is required to establish whether an infection is caused by PJ.2.1.
What does research reveal about the new variant?
A study published in the Journal of Infection examined the epidemiological and virological characteristics of PJ.2.1, including how its spike protein interacts with human cells and how effectively antibodies can neutralise it.
Researchers found that pseudovirus particles carrying the PJ.2.1 spike protein entered four of the five cell lines tested around 1.5 to 2.5 times more efficiently than particles carrying the LP.8.1 reference spike protein.
The study also found increased efficiency in the variant's interaction with the ACE2 receptor, which the coronavirus uses to enter human cells. This characteristic could help explain its spread, although laboratory findings do not establish how readily the virus transmits between people in real-world conditions.
The researchers also examined antibody neutralisation using plasma from people who had received an LP.8.1-adapted Covid-19 vaccine.
Neutralisation of PJ.2.1 was approximately 1.8 times lower than that of the LP.8.1 reference variant. This was a more limited reduction than that observed for several other variants included in the comparison.
The researchers said continued surveillance would be important to identify whether new PJ.2.1 subvariants emerge with greater antibody evasion.
However, the findings are based on laboratory experiments and do not establish that PJ.2.1 causes more severe illness, increases hospitalisation or leads to higher mortality in people.
Who is most at risk from severe Covid-19?
Older people, individuals with weakened immune systems, pregnant women and people with certain underlying health conditions remain at greater risk of serious Covid-19 complications.
Those with cardiovascular disease, diabetes and chronic lung or kidney conditions may also be more vulnerable.
Vaccination remains an important measure for reducing the risk of severe illness and death. People in eligible high-risk groups should follow medical advice on vaccination and seek prompt medical attention if they develop symptoms, particularly where early treatment may be appropriate.
People experiencing respiratory symptoms should limit contact with others while unwell and consider testing where the result could influence treatment or precautions.
Rapid antigen tests can help detect Covid-19, although a single negative result does not always rule out infection. People with symptoms should follow current testing guidance and seek medical advice if they are at increased risk of complications.
Difficulty breathing, severe chest pain or loss of consciousness requires urgent medical attention.
The emergence of PJ.2.1 has added another variant to the ongoing evolution of SARS-CoV-2, but researchers say its clinical impact remains under investigation. For now, the available evidence does not establish that it causes more severe disease than other circulating variants.
