The XFG Covid strain also known as the Stratus or “American Covid” strain, which was first identified last January is back and it has since spread around the world especially in the UK where the UK Health Security Agency (UKHSA) monthly figures show that in August, 1,374 contracted Covid before jumping 230% to 4,589 in September.
XFG COVID-19 Variant: All You Need to Know
XFG, also known as “Stratus,” is a recombinant strain of SARS-CoV-2, the virus that causes COVID-19. It emerged from the Omicron family and has become one of the more widely detected COVID-19 variants globally in 2026. The World Health Organisation currently classifies XFG as a Variant Under Monitoring (VUM) rather than a Variant of Concern.
XFG is not an entirely new coronavirus. It is a recombinant lineage formed from two earlier SARS-CoV-2 lineages, LF.7 and LP.8.1.2. The earliest documented XFG sample was collected in January 2025, and the WHO designated it a Variant Under Monitoring in June 2025.
The variant has attracted attention because of its increasing prevalence and mutations in the spike protein, which can help the virus partially evade antibodies produced by previous infection or vaccination. However, immune escape does not necessarily mean that the variant causes more severe illness.
According to the WHO’s global surveillance data, XFG accounted for a substantial share of submitted SARS-CoV-2 sequences in 2026, with its prevalence increasing significantly over several weeks.
There is currently no strong evidence that XFG causes more severe disease or more deaths than other circulating COVID-19 variants. The WHO has assessed the additional global public-health risk posed by XFG as low and says currently approved COVID-19 vaccines are expected to continue providing protection against symptomatic and severe disease.
Symptoms
The symptoms associated with XFG are broadly similar to those caused by other currently circulating COVID-19 variants. People infected with the variant may experience a sore throat, fever, chills, cough, runny or blocked nose, fatigue, headache and muscle aches. Some people may also develop a hoarse voice, shortness of breath, nausea, vomiting or diarrhoea. Loss or changes in taste and smell can occur, although these symptoms are less prominent than they were during earlier stages of the pandemic.
Reports have particularly drawn attention to sore or scratchy throats and hoarseness among some people infected with XFG. However, these symptoms are not unique to XFG and cannot be used to determine which COVID-19 variant a person has. A COVID-19 test can establish whether someone is infected, while genomic sequencing is generally required to identify the specific variant.
XFG does appear to have some ability to evade existing immunity. Laboratory studies have found reduced neutralisation of the variant by antibodies generated through previous infection or vaccination. This is part of the continuing evolution of SARS-CoV-2 and does not mean that vaccines have become ineffective.
Vaccination remains particularly important because protection against severe disease tends to be more durable than protection against infection. The WHO has continued to recommend vaccination and has said people should not delay vaccination while waiting for a vaccine targeting a newer variant.
Health authorities have also moved to update vaccine formulations in response to the evolution of the virus. The US Food and Drug Administration recommended XFG as the preferred antigen for the 2026–2027 COVID-19 vaccine formulation in the United States, while European regulators have also recommended updating vaccines to target XFG for the 2026/27 vaccination campaign.
