2023-09-17 04:00:00
The mechanisms that can lead to long-term Covid in part of the population remain, even today, a mystery, even if several avenues are favored and studied closely.
In October 2020, Matthieu Lestage, 42, contracted Covid-19 and developed several symptoms of the disease. Two and a half years later, this former soldier was still handicapped by significant following-effects, which sometimes forced him to use a wheelchair.
He suffers from what has been called “long Covid”, i.e. a persistence of symptoms for months, even years, following an infection. “I have coordination problems, memory problems, tremors, a need for permanent rest,” the spokesperson for the long Covid patients association After D20 tells BFMTV.com.
Like him, around 20% of people affected by Covid-19 in France – which is showing signs of recovery – have been for several months, or are still, suffering from long Covid, including a majority of women, according to a Health survey public France. And three years following the first patients of this type, research is still stuck on the reasons for the persistence of certain symptoms in part of the population.
Today “honestly, we are fumbling a little, everyone is fumbling a little”, confides Philippe Azouvi, professor of physical medicine and rehabilitation at the Raymond Poincaré hospital and medical advisor to ARS Ile-de-France.
A difficulty: distinguishing long Covid from another disease
The first difficulty encountered for doctors and researchers interested in long Covid comes from the fact that it is not necessarily easy to identify the disease: there is currently no dedicated test. The World Health Organization defines long-term Covid as “the continuation or development of new symptoms 3 months following initial infection with SARS-CoV-2, these symptoms lasting at least 2 months without any other explanation”. that is to say without other diseases detected.
But the symptoms of Covid-19 are numerous – the WHO lists more than 200 – and are not specific. The most frequently identified are headaches (headaches), fatigue, attentional or memory problems – combined under the term “cognitive fog” – or even shortness of breath during exercise. However, these are symptoms that may correspond to other illnesses.
So for doctors, “the problem is to separate what is really Covid from what is something else”, underlines Philippe Azouvi.
Because “sometimes patients have symptoms, but it is not long Covid, it is because they have another complication, and we must not ignore it because these are different treatments”.
“Many prolonged symptoms can be attributed to Covid,” summarizes Brigitte Ranque, specialist in internal medicine, working on the long Covid circuit set up at the Hôtel Dieu (Paris). But “if there are very disabling, persistent symptoms that are not explained, we speak of long Covid.”
The biggest challenge right now, and what researchers are working on, is understanding how the SARS-CoV-2 virus can cause such damage in infected people.
The trail of a “somatic disorder”
Brigitte Ranque, like other researchers, is working on the possibility of a “functional somatic disorder” in patients with long Covid, a disorder already known before the pandemic. It causes in the patient “the presence of somatic symptoms without organic explanation, without objective lesion of the organ designated by the symptoms”, explained the High Authority of Health at the beginning of 2021.
“These are repeated, lasting or disabling symptoms, leading to a request for care whose major impact contrasts with the absence of clinical or paraclinical anomaly that might fully explain them.”
“These are people who will experience symptoms that are not adapted to the lesions observed,” explains Brigitte Ranque. “There is a disruption in brain functioning”, and the infection would be the triggering factor for this disorder.
The patient then becomes hypersensitive to all bodily signals, which are felt to be very threatening even though the organs are functioning well. Furthermore, the alert state of the brain can itself cause physical symptoms through the activation of the so-called “autonomic” nervous system.
This line of study has been criticized, in particular by patient associations who see it as a denial of their illness, an accusation of simulation, while some of them were confronted with skepticism from doctors at the start of the pandemic.
But Brigitte Ranque assures her, “it is not a question of discrediting patients and saying that they have nothing”, their symptoms “are very real” and there is no question of declaring that they have pretending to be sick.
Persistence of the virus or inflammation?
Other work focuses on an inflammatory possibility, for example “the possibility that the virus has invaded the brain and spreads inflammation”, explains Guilherme Dias de Melo, researcher at the Pasteur Institute, to BFMTV.com. “We are looking to see if the virus is still there and if it has caused damage” in certain areas, which might explain certain symptoms, he summarizes.
The persistence of the SARS-CoV-2 coronavirus in certain parts of patients’ bodies, even if they present negative Covid tests, is also being closely studied.
“There might be a correlation between the length of time the virus stays in the body and the risk of prolonged Covid,” we read in a study published on May 10 in The Lancet.
Research strongly suggests that patients with long Covid do not completely clear the SARS-CoV-2 virus. “Instead, the virus may persist in tissues where it continues to challenge the immune system. This might lead to a wide range of downstream consequences,” also writes The Long Covid Research Initiative, which brings together scientists and patients in research into this disease.
“Microhemorrhages”?
In an article published in September 2022, several researchers write that at present, “three main mechanisms are the subject of intensive research: the persistence of the SARS-CoV-2 coronavirus in the body of patients; the maintenance of ‘an inflammatory state following infection at the tissue level, particularly vessels and brain tissue’, but also ‘the formation of microclots and/or microbleeds’.
“Inflammatory microthromboses or microhemorrhages might occur” in certain organs, which might “result in poor tissue oxygenation and explain sudden episodes of discomfort, pain (muscular, cardiac) or brain fog,” they explain.
“There are many possibilities studied,” says Guilherme Dias de Melo, who emphasizes that the cause of long Covid “appears to be multifactorial”.
The phenomena studied above therefore do not necessarily cancel each other out and might even feed each other. The idea is that there would not be just one mechanism leading to long Covid, “it can be a combination of different factors, it is probably multifactorial”, adds Philippe Azouvi.
“No proven curative treatment”
It is therefore difficult for the moment to provide a response to patients, some of whom remain in medical wandering. Although the law of January 24, 2022 provided for a platform for monitoring long Covid cases, the system has still not been launched. It “must arrive before the end of the year,” assured doctor and Renaissance MP Stéphanie Rist. “Today, we only treat the symptoms,” declares Mathieu Lestage, who explains that his life has deteriorated significantly. If some have managed to recover, or at least see an improvement in their condition over the months, this is not the case.
“There is no proven curative treatment,” says Philippe Azouvi. “Some suggest using anti-inflammatories in the hypothesis that it is an inflammatory process. Some colleagues say that it works but this has never been demonstrated.”
“Otherwise it’s re-education, that’s what we do in the SSR (follow-up care and rehabilitation) centers, it’s exercise retraining, cognitive retraining but there is no There is not much solid evidence today of its effectiveness.”
Philippe Azouvi underlines that three years following the start of the pandemic, long-term Covid patients continue to present themselves in the centers: in 2022, 800 requests were submitted in Île-de-France. “It’s not negligible,” says the doctor, adding that “those we see in rehabilitation are only the small tip of the iceberg.”
And to treat these patients and find a treatment, “we must first understand the mechanisms” of this disease, says Guilherme Dias de Melo.
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