A lingering gastro, persistent fatigue, a few suspicious aches… and could it be Covid? Since the return to school, a curious phenomenon has puzzled general practitioners: the virus is indeed circulating again in France, but it has changed its face. Gone is the classic picture with a persistent cough and high fever that alerted patients and caregivers right away. Now, the infection slips discreetly behind digestive symptoms, fleeting confusion, or disproportionate exhaustion. The result: many people consult without ever thinking to pull out an at-home test. A muddling of clues that raises a real public health question, as epidemic indicators begin to rise again slowly.
- Since September 2026, the XFG variant (“Frankenstein”), born from the fusion of two Omicron lineages, dominates Covid circulation in France and worldwide
- Current symptoms favor digestive disturbances, brain fog, joint pain, and skin rashes, often without cough or fever, which delays diagnosis
- In case of doubt, a rapid antigen test remains useful but a negative result on day one should be confirmed by a second test 48 hours later
- The back-to-school period drives up epidemic curves
- When Covid disguises itself as gastro or as a bout of fatigue
- The signals that should push you to take an at-home test
The back-to-school period drives up epidemic curves
Like a déjà vu every year, the return to school gatherings at the start of September is accompanied by a rise in Covid indicators across France. Medical consultations, visits to emergency departments and hospitalizations are slightly up in all regions, while the viral concentration detected in wastewater—the earliest signal for following the evolution of an outbreak—also increases. Nothing alarming, however: the epidemic level remains described as weak and controlled by the health system. A new variant, nicknamed Frankenstein or XFG, has established itself as the dominant form in circulation since autumn 2025, not only in France but also in Europe, Asia, North America and Oceania. Born from the unexpected fusion of two Omicron lineages, it carries novel mutations on the Spike protein that would allow it to enter cells more easily, partly explaining its rapid spread. Surveillance of this strain is now integrated into the overall monitoring of acute respiratory infections, alongside influenza and bronchiolitis, proof that Covid is no longer treated as an isolated threat but as one actor among others in the virus season.
When Covid disguises itself as gastroenteritis or as a bout of fatigue
That is where the story becomes truly interesting. The clinical picture of Covid has gradually shifted since the appearance of Omicron, with an increasing share of signs that are no longer respiratory. Loss of smell and taste, once the emblematic symptom of the early waves, has become almost invisible. As for the cough-and-fever duo, it becomes the exception rather than the rule. Instead, isolated digestive disturbances, nausea, diarrhea, abdominal pains, sometimes appear as the first and only sign of infection. This is not a French peculiarity: in 2026, these same symptoms were reported in several Asian countries among positive patients, notably infected by a related sub-variant. Added to this picture are diffuse joint and muscle pains, unusual skin rashes, and above all a brain fog that now arrives in the acute phase, whereas it used to be mainly associated with long Covid. Direct consequence: many patients consult for gastroenteritis, an influenza-like syndrome, or a simple bout of fatigue, without ever considering a Covid test. A genuine missed diagnostic window sets in, allowing the virus to circulate much more quietly than official figures suggest. Among children, pediatric teams also observe a higher frequency of these same digestive troubles and skin manifestations, signs largely absent during previous waves.
The signals that should push you to take an at-home test
In the face of this new face of the virus, it is better to learn to recognize the right combinations of symptoms rather than wait for a fever that may never come. It is not a single sign that should alert, but rather the sudden combination of several unusual manifestations.
- Sudden digestive disturbances, with no obvious dietary cause, accompanied by body aches
- Unusual brain fog, with concentration or memory difficulties
- Migrating joint pains coupled with disproportionate fatigue
- Unexplained skin rashes, sometimes in the form of red patches
Good news nonetheless: rapid antigen tests remain available in pharmacies and still detect the majority of cases when the viral load is sufficient. One caveat, a negative test on the first day does not rule out infection; a second test performed 48 hours later is still recommended if doubt persists. This detection issue is not trivial: in France, long Covid would today affect around two million people, with heavy symptoms such as extreme fatigue, respiratory or cardiac problems, or a loss of muscle strength. A reminder that vigilance regarding acute forms, even discreet ones, is not excessive.
Recognizing these atypical symptoms and not hesitating to test as soon as any doubt exists helps limit this silent spread that complicates the work of health authorities. While awaiting updated recommendations, staying attuned to the faint signals sent by one’s body remains, for now, the best compass.
