A new variant of COVID-19, designated XFG, is circulating in the city of Rio de Janeiro. A total of 46 cases of this variant were identified among samples analyzed by the Oswaldo Cruz Foundation (Fiocruz) as part of a surveillance initiative in partnership with the city’s Municipal Health Department (SMS). These cases represent 62% of the 74 genomes examined from individuals diagnosed with Covid-19 between 1 and 8 July.
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Mild Cases
All identified cases of the XFG variant were classified as mild, requiring no hospitalization and resulting in no fatalities. According to Rio de Janeiro’s Secretary of Health, Daniel Soranz, high vaccination coverage has played a crucial role. All individuals infected with the new variant were fully vaccinated against COVID-19. The symptoms associated with XFG are consistent with those of other variants. Among vaccinated individuals, as in these instances, symptoms lasted between five and seven days and remained mild in intensity.
Three Cities Reporting the New Variant
According to the State Health Department, the XFG variant has also been identified in residents of two other municipalities: Petrópolis (1 case) and Rio das Ostras (1 case), in addition to the 46 cases found in Rio de Janeiro. Despite the presence of this new variant, authorities have not issued an alert, citing no substantial increase in the number of COVID-19 cases across the state.
COVID-19 Cases in Rio
Data from the city’s epidemiological dashboard, updated daily, indicates that 5,823 COVID-19 cases have been confirmed in Rio de Janeiro so far this year. Of these, 147 were classified as severe, including seven this month alone. The city has recorded 22 COVID-19-related deaths in 2025, with the most recent occurring on June 25. The specific variant involved in these deaths was not reported.
It’s Not Just a Common Cold
COVID-19 symptoms, regardless of the variant, can be easily mistaken for other respiratory illnesses. As winter began on June 20, health officials are warning that transmission may rise due to common seasonal behaviors—such as keeping windows closed and reducing indoor ventilation—which facilitate the spread of respiratory viruses.
Analysis:
The detection of the new XFG variant in Rio de Janeiro demonstrates the continued evolution of the SARS-CoV-2 virus and the importance of maintaining genomic surveillance, even in the context of declining hospitalizations and fatalities. The fact that 62% of recent sequenced samples belong to this new lineage suggests rapid dissemination within the city. However, the absence of severe cases or deaths linked to XFG so far indicates that, thanks to widespread vaccination, the population is relatively protected from serious outcomes.
Nevertheless, it is premature to treat this development as routine. Although current cases remain mild, the emergence of a new variant always carries the potential for changes in transmissibility or immune escape. Authorities must remain vigilant, particularly during the winter months, when the risk of respiratory virus transmission tends to increase.
Sources: O Globo.
