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Covid cases are climbing again in Spain and the XFG variant is now the strain doing most of the circulating, according to the latest surveillance figures and the experts analysing them.

 

The Carlos III Health Institute's Acute Respiratory Infection Surveillance System (SiVIRA) recorded 493.8 cases per 100,000 inhabitants between September 28 and October 4, which is 3.3% more than the 478.2 of the week before. Redacción Médica reported that the level of intensity is still classed as low, although incidence has now edged up over several weeks, with respiratory infections jumping 28.2% in week 39 and Covid alone approaching 120 cases per 100,000.

 

The Spanish Society of Infectious Diseases and Clinical Microbiology (SEIMC) explained that the increase in transmission is real and not a statistical blip.

 

XFG is the dominant lineage in Spain and much of Europe, with the European Centre for Disease Prevention and Control (ECDC) estimating that it made up around 54% of sequences in countries with enough data in weeks 34 and 35.

 

In Spain it accounted for around 69% of the variants characterised in primary care and 65% of hospital samples, although the SEIMC pointed out that proving the rise is down to XFG alone is much harder.

 

Hospital admissions haven't been affected so far and according to the society there's no evidence that XFG causes more severe illness than the other Omicron variants in circulation. It did add a note of caution, as a more transmissible variant can still lead to a lot of hospital admissions simply because it infects more people, even when the risk of severe illness hasn't risen.

 

XFG is a recombinant lineage in the Omicron and JN.1 family, formed when two Omicron sublineages combined. The World Health Organisation labelled it a variant under monitoring in June 2025 because it had a growth advantage over other strains, but it doesn't class it as a variant of concern.

 

Its spike protein carries several mutations, some in areas linked to how antibodies work, although studies so far suggest its ability to dodge immunity is only slightly different from other JN.1 descendants.

 

There's no specific set of symptoms that sets XFG apart from other variants. The usual signs of recent strains still apply, including a sore throat, runny or blocked nose, cough, fever or chills, headache, muscle aches and tiredness, while loss of smell or taste is far less common than in the early days of the pandemic.

 

The SEIMC named five reasons for the continuing rise in cases. XFG spreads more easily and has the advantage of being the dominant strain, while protection from vaccines and past infections fades over time. Social contact increases as summer ends and routines return, the coronavirus follows a seasonal pattern of recurring waves, and several sublineages are circulating at the same time instead of a single variant.

 

 

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