Many people report symptoms persistent for several months after being infected with SARS-CoV-2. This “post-Covid” state is still poorly understood but is currently the subject of rigorous research in order to better define its prevalence in the general population and to decipher the underlying physiopathological mechanisms.
From persistent symptoms which have been most often described in the scientific literature are the dyspnea (breathing difficulty), theasthenia (fatigue), pains joints and muscles, cognitive problems, digestive disorders, or even anosmia-dysgeusia (loss ofsmell and taste).
Apart from this last symptom, these are clinical manifestations that are not specific to the Covid-19 and which could, for example, be linked to other infections contracted over the same period or to more restricted access to the health system during the pandemic. In order to better understand and better manage the “post-Covid” state, it is therefore essential for scientists to determine which persistent symptoms are more closely associated with SARS-CoV-2 infection.
A study representative of the general population
Conducted by researchers from Inserm, Paris-Saclay University and Sorbonne University at the Pierre-Louis Institute of Epidemiology and Public Health, in collaboration with ANRS-Emerging Infectious Diseases, the new study published in journal The Lancet Regional Health – Europe looks into this question. This study first draws its originality from the fact that it was carried out in a cohort in the general population. General population cohorts differ from cohorts constructed from samples of Covid patients (by definition all “symptomatic” and often with severe clinical forms or hospitalized), which are not representative of all infected people.
This type of cohort therefore makes it possible to understand public health issues by developing comparative groups, for example according to the severity of the symptoms presented at the time of infection. The other originality of the work is that all the participants benefited from a serological test a posteriori to search for a history of SARS-CoV-2 infection. This differentiates this work from most of the work that has been done on the subject, which focuses on people who have made a PCR test and who have exhibited symptoms.
Thus, this work makes it possible to compare the persistence of symptoms seven to eight months after the first vague of the pandemic in four groups of participants divided according to the symptoms they had had during this first wave and their serological status (whether or not testifying to infection with SARS-CoV-2).
The first group of participants included all people with a positive serological test for Covid-19 and who reported symptoms during the first wave. In the second group, the individuals had a positive test but no symptoms. The third group were those with a negative serological test and symptoms while the fourth group was asymptomatic during the first wave, with a negative serological test.
Variability of symptoms according to serological status
From the Constances cohort, 25,910 participants answered two questionnaires during the first wave of the Covid-19 pandemic, in order to determine the presence of symptoms in the preceding fifteen days. A serological test was then carried out for each of them, between May and November 2020, in order to identify the people who had been exposed to the virus.
Finally, between December 2020 and February 2021, a third questionnaire on symptoms that have persisted or persisted for at least two months was offered to participants. This questionnaire included the list of symptoms sought during the first waves of questionnaires, but also new symptoms of which people with “long Covid” complain (disorder of concentration and attention, chest pain, etc.).
The researchers compared individuals who presented symptoms suggestive of an acute respiratory infection according to their serological results. They observed that people who were symptomatic and had positive serology had moreanosmia–dysgeusiapersistent dyspnea and fatigue than individuals seronegative for SARS-CoV-2. The other symptoms had an equivalent frequency.
Persistence of symptoms related to time of infection
The authors then explored the link between infection, acute symptoms and persistent symptoms. The results of their statistical analyzes show that infection with SARS-CoV-2 essentially has an effect on the persistence of symptoms if it induces certain symptoms at the time of the acute episode of infection.
” Our results confirm the importance of the clinical expression of the initial infectious episode in the risk of developing persistent symptoms. They can help guide public policies by providing more precise data on the type of persistent symptoms of Covid-19 and by encouraging the development of more effective management strategies. Promote therapies and preventive approaches, such as the vaccination, which reduce symptoms during the acute phase of the disease could also have a beneficial effect on post-Covid states “, underline the authors of the study.
These results testify to the complexity of the mechanisms that may explain the persistent symptoms, highlighting that these symptoms may be related to the virus, the initial clinical presentation of the infection and other non-specific causes. They also suggest the importance of conducting studies on post-infectious states, whatever the microorganism incriminated.
Further work is underway to understand the mechanisms underlying these “post-Covid” states and to quantify the proportion of these persistent symptoms attributable to SARS-CoV-2 infection.
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