The new SARS-CoV-2 variant XFG (also referred to as Stratus) causes hardly any difference in symptoms than previous variants of the coronavirus. Similarly, the symptoms do not seem to be more severe. This is the result of an exploratory study by RIVM among Infection Radar survey participants.
Same sore throat, less loss of taste
Recent media reporting suggested that XFG was more likely to cause sore throat and more severe symptoms. RIVM decided to explore this based on data from Infection Radar. In Infection Radar, a large group of people fills out a weekly survey on symptoms that could indicate a respiratory infection. This makes it possible for RIVM to monitor the spread of infectious diseases. RIVM has now compared the COVID-19 symptoms of two groups of Infection Radar participants:
- participants who tested positive for COVID-19 in July through September 2025, when the SARS-CoV-2 variant XFG was prevalent.
- participants who tested positive for COVID-19 in July through September 2024, when the SARS-CoV-2 variant KP.3 was prevalent.
The Infection Radar data shows that participants reported a sore throat this summer in the same frequency as last year: 84% in 2025 and 71% in 2024. The number of symptoms reported by participants and how ill they felt were also about the same. Participants reported 7.8 symptoms on average in 2025 and 7.6 in 2024. Loss of taste occurred less frequently in 2025.
Hardly any difference in symptoms than before
Virologist and researcher Dirk Eggink (RIVM): “Sore throat is a common symptom of COVID-19, but is not more frequent in the XFG variant than in previous variants. Reported frequency of other symptoms, such as sneezing, coughing and a nasal cold, also hardly changed at all. The severity of the symptoms was the same. There are no indications that participants perceived the sore throat as more severe.”
Take part in Infection Radar!
Would you like to take part in Infection Radar? You can! A quick weekly check with the Infection Radar survey helps RIVM to detect viruses in time. Staying alert to symptoms together means we can keep each other healthy! Infection Radar is easy and only takes three minutes a week. For more information and registration details, go to www.infectieradar.nl.
About the study
Infection Radar has nearly 11,000 participants. In the past few weeks, there has been a significant increase in participants reporting respiratory symptoms. That is normal for this time of year. Some of the participants have COVID-19, but other viruses can also cause symptoms.
For this study, RIVM analysed the data of people who took part in Infection Radar and who had a COVID-19 infection that was confirmed by a positive test. Every week, participants reported their symptoms and how healthy they felt on a scale of 0 (very ill) to 100 (as healthy as possible). If they had symptoms, the participants used a COVID-19 self-test. Sometimes they also sent in a nose and throat swab for further assessment.
New variants are not automatically more severe
The study confirms previous research results. New SARS-CoV-2 variants like XFG do not automatically lead to more severe disease than previous variants. Since the arrival of Omicron, the main symptoms are sore throat, coughing and sneezing. On average, COVID-19 is still more serious than a common cold and is more comparable to influenza (flu).