There is "concrete evidence that different organs undergo changes" after a Covid-related hospitalization, Christopher Brightling, co-author of a study published Friday in the Lancet Respiratory Medicine, said at a press conference.

This work is based on MRIs performed on 259 patients who were hospitalized for Covid in 2020-2021. They were compared with examinations carried out on about fifty people who had never been infected.

Nearly a third of Covid patients had "abnormalities" in several organs, several months after they were discharged from hospital. These organs include the brain, lungs or kidneys and, to a lesser extent, the heart and liver.

For example, researchers have identified lesions of the white matter of the brain, a phenomenon that may be associated by the scientific literature with a slight cognitive decline.

For the authors of the study, as well as independent observers, these results open a track of explanation for the long Covid, that is to say the persistence of lasting sequelae several months after infection.

This disorder, which however lacks a consensual definition, is still poorly understood physiologically, several explanations competing with each other without necessarily being exclusive.

The study made public Friday suggests that the long Covid "is not explained by serious deficiencies concentrated on a single organ" but rather "an interaction between at least two abnormalities of (different) organs," says pulmonologist Matthew Baldwin, who did not participate, in the same issue of Lancet Respiratory Medicine.

-the brain track-

Another study, published a week earlier in the journal eBiomedicine, has rather opened the track of a mechanism concentrated in the brain.

Conducted by a team from Inserm, the French National Institute of Health and Medical Research, this study looked at about fifty patients, some of whom suffered a drop in their testosterone levels, linked to an alteration by the virus of certain neurons regulating reproductive functions.

A study is based on MRI scans performed on 259 patients who were hospitalized for Covid in 2020-2021 © Alain JOCARD / AFP / Archives

The researchers then measured the cognitive functions of these patients, to find poorer performance when this category of neurons was affected.

These results, "suggest that the infection can lead to the death of these neurons and be the cause of certain symptoms that persist over time," says Inserm in a press release.

Fatigue, cough, shortness of breath, intermittent fever, loss of taste or smell, difficulty concentrating, depression... Long Covid manifests itself as one or more symptoms from a long list, usually within three months of infection and persisting for at least two months. Symptoms that cannot be explained by other diagnoses and have an impact on daily life.

In France, "long Covid" affected 4% of adults or 2.06 million people over the age of 18, with a small proportion (1.2%) saying they were severely hampered in their daily activities, according to a study by Public Health France conducted last autumn and whose results were unveiled in June.

The vast majority of patients (90%) suffering from long Covid, however, see their symptoms slowly improve after two years, the others experiencing a rapid improvement or on the contrary a persistence of their disorders, says a study published in May by Dr. Viet-Thi Tran, epidemiologist (University Paris Cité / AP-HP), among 2,197 patients of the "ComPare" cohort suffering from long Covid, Follow-up regularly.

© 2023 AFP