New Covid variant 'Stratus' on rise in US, UK: What are the symptoms?

Covid-19

As the weather begins to change and respiratory illnesses become more common, a highly transmissible strain of Covid-19 is on the rise across the United State and the United Kingdom.

Nineteen states in the US are seeing “high” or “very high” levels of the XFG Covid-19 variant, known as Stratus, in wastewater, according to Centers for Disease Control and Prevention (CDC). Nevada, Utah, Connecticut and Delaware reported the highest levels. It is also accounting for a high proportion of cases in England.

With this, Stratus variant and NB.1.8.1, known as Nimbus, are now the most common variants being passed around in the UK, according to officials, BBC reported.

What experts say?

However, despite accounting for a large proportion of new cases, experts are not concerned about the spread, noting it is normal for viruses to mutate and change.

“It is normal for viruses to mutate and change over time,” Dr Alex Allen, consultant epidemiologist of the UK Health Security Agency (UKHSA), said, adding that it continues to monitor all strains of Covid in the UK, according to a report by the Independent.

By 10 September, the UKHSA noted a 7.6 per cent increase in coronavirus cases across England compared to the previous week, although it’s uncertain how many are linked to the XFG variant.

What is ‘Stratus’ XFG and XFG.3?

Stratus has two main variants – XFG and XFG.3. The World Health Organisation (WHO) has designated the XFG as a “variant under monitoring” and has said the additional public health risk posed by XFG is evaluated as low at the global level.

Globally, XFG was estimated to have the highest relative growth compared to other variants currently circulated, including the recent “Nimbus” NB.1.8.1.

What are the symptoms of Stratus?

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, according to a report by NDTV.

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.