Covid long: several hypotheses to explain this phenomenon that affects millions of people

published on Sunday 02 October 2022 at 07:00

The long Covid manifests itself with symptoms such as chronic fatigue, shortness of breath or even brain fog, several months after a Covid-19 infection, many teams are working around the world to understand the causes.

The “long Covid” remains a mystery for research, even if several hypotheses are on the table to explain it This phenomenon affected, in 2020 and 2021, 145 million people worldwide, according to the Institute for Health Metrics and Evaluation, based in the United States.

Europeans are “at least 17 million” affected, according to a recent estimate by the World Health Organization (WHO). this would represent between 10 and 20% of people who have been infected with the virus.

Tiredness, cough, shortness of breath, intermittent fever, loss of taste or smell, difficulty concentrating, depression… the long Covid is manifested by one or more of a long list of symptoms, usually within three months of infection. infection and persistent for at least two months. The syndrome affects twice as many women as men. “There are no really specific symptoms of prolonged Covid, but they still have certain characteristics: they are fluctuating with a tiredness that remains in the background, they seem to be exacerbated after an intellectual or physical effort and become scarcer over time, ”summarizes Olivier Robineau, infectologist at the Tourcoing hospital center and long Covid coordinator at the National Agency for Emerging Infectious Diseases . diseases.

Many teams are working around the world to understand the causes of these symptoms. In France, for example, the Hôtel-Dieu hospital (AP-HP), the University of Paris and Inserm launched a study at the end of 2020 on long Covid within the “ComPaRe” cohort: “2,500 patients are monitored very regularly, ce qui devrait nous permettre de comprehend les variations des manifestations de la maladie au cours du temps”, explains Dr Viet-Thi Tran, co-investigateur of the cohort. More la variabilité de symptômes et leur charactère non spécifique rend la recherche difficile. Until now, Various hypotheses are studied by scientists.

various hypotheses

One of them is the persistence of the virus in the body in some individuals. Thus, in early September, a study published in “Clinical Infectious Diseases” concluded that the Spike protein (the key that allows SARS-Cov 2 to enter cells, editor’s note) was present in patients with long-term Covid. . This suggests viral replication or the persistence of viral remnants long after the initial infection. A live virus or virus remains could maintain an inflammatory activity, perhaps at the origin of the symptoms. These results, however, are not not found by other teams.

There are other ways. The virus would have disappeared after infection but the initial inflammation, once started, would have caused a dysregulation of the immune system. The so-called “tissue damage” hypothesis evokes the role of the initial infectious episode in the appearance of lasting lesions in certain organs. Studies have further shown damage to blood vessels as a result of infection.

A care course at the Hôtel-Dieu

For each of these hypotheses, the data is still not very solid,” says Olivier Robineau, betting that “we are not going to find a single cause to explain the long Covid”. “The causes may not be exclusive, they may be associated, even occur in the same individual and be different in different individuals,” he says. Therefore, it is difficult to find a solution for these long Covid patients.

At the Hôtel-Dieu in Paris, a protocol called “CASPER” has been offered for a year a care course to patients for half a day: “They meet a specialist in infectious diseases or an internist, a psychiatrist and then a specialist in sports rehabilitation”, explains Professor Brigitte Ranque, a specialist in internal medicine, at the origin of this circuit. “In the team’s experience, most symptoms can be attributed to ‘functional somatic disorders’ (symptoms result from an imbalance in the functioning of the central nervous system, editor’s note). The behavior is often associated with supervised physical activity “. “Patients are called three months later: most are better, more than half say they are cured,” Professor Ranque details. “But about 15% don’t get better at all,” he admits.

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