All About COVID-19 Variant 'Stratus' That Is Fuelling Cases In US

The XFG 'Stratus' COVID-19 variant has been spreading in the US, with cases surging across the country, Today reported. As per the Centers for Disease Control and Prevention (CDC) data, published on September 20, the level of Covid viral activity in wastewater is "moderate" nationally. Notably, 19 states are reporting "high" or "very high" levels of the virus in wastewater, including Nevada, Utah, Connecticut and Delaware.

The CDC's Nowcast estimated that XFG accounted for less than 3% of infections in the US in early May. But it surged afterwards, and this variant accounted for an estimated 85% of COVID cases during the four weeks ending September 27.

COVID-19 cases have also been reported in the United Kingdom, fuelled by XFG and NB.1.8.1, known as Nimbus, BBC reported.

"Our genomic surveillance of SARS-CoV-2 lineages last month found that 35% were classified as XFG.3, 28% were classified as XFG, 11% were classified as NB.1.8.1, 7% were classified as XFG.5 and 7% were classified as XFG.3.4.1," UK government data noted.

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All about Stratus (XFG) variant

According to a document published by the World Health Organization (WHO) on June 25, XFG was designated a SARS-CoV-2 variant under monitoring.

XFG, a hybrid of two Omicron sub-strains, was first detected in Southeast Asia in January 2025. It spread globally, becoming predominant in the US. The variant is considered slightly more transmissible, partly due to immune evasion properties.

Available data suggest XFG isn't causing more severe disease than previous Omicron variants. In fact, the WHO states existing COVID-19 vaccines are expected to remain effective against symptomatic and severe disease.

WHO's June document mentioned that the currently approved COVID-19 vaccines are expected to remain effective against this variant against symptomatic and severe disease. But a BBC report noted that a key US vaccine advisory committee has voted to stop recommending that all adults get the COVID-19 vaccine, which earlier was officially approved for most Americans annually since the pandemic. The Advisory Committee on Immunization Practices (Acip) also narrowly voted against advocating prescriptions for the Covid vaccine.

Symptoms of Stratus (XFG) Variant

Some of the common symptoms are sore throat, cough, congestion or runny nose, fever or chills, shortness of breath, fatigue, headache, muscle aches, nausea, vomiting or diarrhoea.

Some reports highlighted hoarseness as a distinctive symptom associated with Stratus, which might be mistaken for allergy symptoms. Loss of taste or smell is still possible but reportedly less common compared to earlier variants.