why the disease carries long-term health risks, even after mild forms

“Living with the virus”. When it appeared, this catchphrase described the distant future. Now he summarizes the attitude adopted in most European countries, including France, where health restrictions have practically disappeared. More than 130,000 people test positive for Covid-19 every day, a total never reached before the end of 2021, but the topic has disappeared from public debate. However, the virus has not ceased to be dangerous. It still kills 101 people a day on average, most of them vulnerable or unvaccinated. A series of recent studies has also lifted the veil on its long-term effects: after an infection, the risk of other pathologies increases, even for those who do not present a risk factor, do not develop a severe form and are not affected by the infection. Long covid.

In April 2021, a first study by three researchers from the University of Saint-Louis (United States), published by the journal Nature*, identified a myriad of health conditions that affected people who had Covid-19 most often. Using an extensive US Army veterans health database, the authors compared nearly 5 million people who were not sick and 77,000 people who tested positive, starting at day 30 after infection. Five months later, they had more breathing problems and also suffered more “neurocognitive and nervous system disorders, mental health, metabolism, cardiovascular, gastrointestinal, malaise, fatigue, musculoskeletal pain, and anemia” than people with a similar profile who have never tested positive. Even non-hospitalized patients had this risk of sequelae.

Since then, this database has been used by the same team for several studies, including one on cardiovascular risks, published in February in Nature*. “Shows a risk multiplied by 1.5 or 2 in all events”, not only the well-known cardiac inflammations in patients with Covid-19, observes Ariel Cohen, former president of the French Society of Cardiology. In people who test positive (more than 150,000 have been observed), the risk of stroke is thus multiplied by 1.52 in the year following infection, the risk of pulmonary embolism by 2.93, that of acute coronary syndrome by 1.72.

“At the beginning of the pandemic we thought that Covid-19 was simply a source of imbalance of the existing risks”recalls Ariel Cohen. In other words, people predisposed to these problems declared them due to a Sars-CoV-2 infection. The results of these American researchers are “a surprise”recognize.

“This study shows that there is a risk compounded by the infection itself and that it doesn’t go away over time as we thought.”

Ariel Cohen, former president of the French Society of Cardiology

on franceinfo.fr

Although it is not entirely clear how the virus causes such sequelae, observation of patients has already shown “that the virus attacks the wall of the blood vessels”which in particular favors the appearance of clots, explains Olivier Robineau, a specialist in infectious diseases at the Tourcoing hospital (North).

Patients cured of Covid-19 also have a higher risk of developing kidney-related pathologies, according to a study by the same US team, published in November in the journal Journal of the American Society of Nephrology*. The data point in particular to a risk of terminal renal failure multiplied by three in ex-Covid-19 patients (and by 2.15 in those who have not been hospitalized). In fact, because it creates vascular problems, the virus can affect a large number of organs. “All these organs are vascularized. As soon as the function of the artery is altered, there is a risk that they will be affected”explains cardiologist Ariel Cohen.

In the minds of the general public, Covid-19 is more associated with symptoms such as loss of taste and smell. But they point out that the virus also affects the brain and nervous system. Long-term Covid patients in particular report difficulty concentrating and a form of “brain fog”. A study on the brains of monkeys infected with the virus, published April 1 in NatureCommunications*showed damage “can drive [à ces] long-term neurological symptoms of long Covid”even in animals that have not developed a severe form.

“Researchers warn of a risk of dementia” favored by the damage caused by the virus, reports Olivier Robineau. The authors of an article published by the magazine Science* in January, note that the damage seen in some patients “They raise the possibility that the infection may accelerate or trigger the future development of neurodegenerative diseases such as Alzheimer’s or Parkinson’s disease.”

This hypothesis remains for the moment more vague than that of cardiovascular problems, clarifies Olivier Robineau, who recalls that these disorders would take years to appear. However, health data for U.S. veterans finds a higher risk of cognitive decline (1.8 times) or depression (1.39 times) in the year after infection, according to a study published February 16. for him British medical journal*.

This statistical approach has limits. A latest study of these data, published March 21 in the lancet*, notes that people cured of Covid-19 are more likely (+40%) to develop type 2 diabetes in the following year. The pandemic will go away “a legacy of chronic disease”says its main author, Ziyad Al-Aly, in Nature*. Eric Renard, vice president of the Francophone Diabetes Society, sees no indication that the virus itself causes diabetes.

“The most obvious link is a disclosure link. Covid-19 puts stress on the body, which can reveal latent diabetes.”

Eric Renard, Vice President of the Francophone Society of Diabetes

on franceinfo.fr

The possibility that the virus is only a trigger is recognized by American scientists and corresponds to what is observed after other infections. Eric Renard does not believe in the risk of an epidemic of type 2 diabetes: “These patients will simply have discovered their diabetes in an unusual way, with immediate insulin treatment, but they will fall in line.” The study has the merit, he judges, of drawing the attention of doctors to the interest in measuring the blood glucose of people cured of Covid-19, especially if they have other risk factors for diabetes.

“You have to stay calm”, alleges infectious disease specialist Olivier Robineau. Recent studies show “an indisputable excessive risk” certain pathologies for patients with Covid-19, “But in events that are still rare. We’re not going to have an epidemic of pulmonary embolism.” Also remember that other elements, such as tobacco and diet, are risk factors that weigh much more in the development of cardiovascular diseases, for example.

“There is no reason to scare people in whom the infection has resolved and who are perfectly well”adds Jérôme Larché, a reference for the follow-up of the long Covid in Occitania. “You just have to encourage them to ask if there’s a problem.” Before tracking all the people cured of Covid-19, it is already necessary to identify and guide those who face prolonged symptoms, a “big challenge”, he explains. another priority “It is to make up for the delay in the care of many patients due to the pandemic”recalls cardiologist Ariel Cohen.

The study of the aftermath of Covid-19 is also only in its infancy. Other works should confirm them and refine the measurement of the risks caused by Covid-19, on more representative populations than veterans of the US army, an older and male audience than the average.

These Covid-19 risks remain, moreover, according to these same studies, proportional to the severity of the disease: a reassuring observation while the increase in the Omicron variant and vaccination have reduced the proportion of severely affected patients. But for Jérôme Larché, what we know about the consequences encourages “Activate all possible levers to avoid contamination, from the vaccine to the use of a mask”. “Covid-19 is anything but a small temporary infection without consequences”remember.

* Links followed by an asterisk lead to publications in English.

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