First there are the alarming facts. As the United States registers more than 270,000 cases of Covid-19 per week, other respiratory viruses threaten to put the American health system under high pressure. Indeed, somewhat forgotten over the past two years, the flu and bronchiolitis epidemics are making a comeback, earlier than expected and simultaneously. Pablo Murcia, professor of integrative virology at the University of Glasgow, does not hesitate to confide in the Wall Street Journal that “during the next winter season, the load of infections will be high”.

As for the respiratory syncytial virus, which causes bronchiolitis, winter is already here. The country’s pediatric services are overwhelmed and Juan Salazar, chief physician of a children’s hospital in Connecticut, confesses on CNN to have “never seen this”. Very contagious, RSV is transmitted in the same way as a cold, of which it shares the symptoms. But it poses a risk in infants under the age of two, who see their bronchioles – the bronchi of very young children – severely attacked by the virus. The flu is also making a remarkable comeback, after two winter seasons in decline. Director of the National Center for Immunization and Respiratory Diseases, José Romero told AFP that the United States is currently facing “the highest rate of flu-related hospitalizations in a decade”.

Then there are the reasons, not yet fully defined. Why could the winter of 2022 see a triple epidemic break out, in the United States, but also elsewhere? Doctors agree to note a difference compared to the ordinary, the various viral infections having rather the habit of succeeding one another and not of accumulating, as is currently the case. They offer several lines of thought. “Wearing a mask, respecting barrier gestures and limiting movement has slowed the spread of the flu virus, but from the moment all this disappears, we logically observe a return of contagions”, indicates to L’Express Yves Buisson, president of the Covid-19 scientific watch unit of the National Academy of Medicine.

For epidemiologist Katelyn Jetelina, interviewed by the Wall Street Journal, “Covid-19 may have prevented the transmission of the flu virus for a time, but now that the Covid has reached a plateau, the flu is coming back”. Professor Aubree Gordon, an epidemiologist at the Michigan School of Health, in the same journal, estimated that the three viruses had “little interference between them”, and that they could therefore “overlap each other, causing co-infections”.

If each of these viruses is no more dangerous than in the past, the combination of two, or even all three, can lead to serious consequences. In addition, Dr. Ellen Foxman, of Yale University’s immunology laboratory, fears in the Wall Street Journal that “infecting a person with one of these viruses makes him more vulnerable to contamination. by another similar virus”. There is nevertheless hope, according to the American newspaper: that of a capacity for resistance residing in what is called the innate immune response. When a foreign agent enters our organism, our body reacts instinctively, before adapting its defenses to the evil in question. This first response of the body could prevent two joint contaminations.

Finally, there is the right protective reflex to adopt: vaccination. “People vaccinated against influenza and Covid are protected against serious forms of these two diseases”, recalls Yves Buisson. Advice in the form of anticipation of future difficulties, because the situation, today worrying in the United States, could well become that of France tomorrow. On the Covid-19 front, the positivity rate remains high in mainland France. Regarding bronchiolitis, it is, according to Public Health France, in a phase “of very significant, rapid and early increase”, while the flu, still at its basic level, should unfold over the winter, if we are to believe the situation in the southern hemisphere, which often reveals our future.