So many questions: the mysterious, silent epidemic of long COVID

The first cases were documented in July 2020, between the first two waves of the COVID-19 pandemic. Since then, long-standing COVID—also known as post-COVID-19 disease or post-COVID syndrome—has been one of the most extensively studied diseases, with nearly 600 clinical studies conducted worldwide. Half of these have tested potential therapies, so far to no avail.Despite these research efforts to better understand and treat long-standing COVID, “There are still many unknowns,” said Dr. Emilia Liana Falcone, director of the post-COVID-19 research clinic at the Institut de recherches cliniques de Montréal (IRCM). “Everything points to a deregulation of the immune system in the direction of autoimmunity,” observed the infectious disease specialist, who points to other proven characteristics such as viral persistence in the body, underlying issues with the intestinal microbiota and inflammation of the blood vessels. “There is also a difference between men and women, biologically and immunologically,” specifying that the latter are more at risk.Are you or any of your patients, dealing with long COVID? We'd like to hear from you for a future featureThe particularity of long-onset COVID, which complicates the work of front-line physicians, “is its very great clinical heterogeneity, which makes it tricky to diagnose,” said Dr. Alain Piché, who heads the post-COVID-19 clinic at CIUSSS de l'Estrie. Intense and sometimes incapacitating fatigue, post-exertion malaise, mental fog, memory disorders, myalgias and arthralgias, sensory disturbances, cutaneous, visual or auditory hypersensitivity, stomach aches, chest discomfort or pain, cardiac dysautonomia, anxiety or post-traumatic stress, sufferers present a wide range of symptoms, with well over 100 having been recorded."The difficulty is that they are non-specific. So we have to go by trial and error, making a diagnosis by exclusion," pointed out the microbiologist-infectiologist.To add to the complexity, these symptoms can vary over time, fading or intensifying, disappearing or reappearing. What's more, some patients have had previous medical problems worsen and persist after contracting COVID-19, but it's not known whether it was COVID-19 that worsened their previous condition or whether it engendered the long COVID. Others have concordant symptoms, “but since people no longer test for COVID-19, that complicates things even more,” said Dr. Piché.Significant prevalenceWhat is known with certainty is that a significant number of patients suffer from it and are severely affected, with half having symptoms persisting for more than two years. According to data from the Canadian COVID-19 Health and Antibody Survey, conducted in the summer of 2024 by Statistics Canada, 16.7% of adults reporting confirmed or suspected SARS-CoV-2 infection presented with post-COVID-19 syndrome. And more than half, “reported notable limitations in the performance of [their] daily activities.”A study by the Institut national de santé publique du Québec (INSPQ) of 6,000 healthcare workers infected with COVID-19 between the start of the pandemic and June 2023 showed that 15% reported symptoms persisting for 12 weeks or more after the initial infection. At the time of the survey (August 2023), “an estimated 6% of all healthcare workers in Quebec were still showing symptoms [of post-COVID-19 illness],” and a third had at least one severe symptom.Scientific co-director of the Long COVID Web pan-Canadian research network, Simon Décary, collaborated on a two-year clinical follow-up study of 4,000 patients diagnosed with long COVID. He estimates that the probability of developing it is closer to 5%. This figure is “closer to reality,” notably because vaccination reduces the incidence of long-onset COVID, as well as the severity and duration of its symptoms, explains the physiotherapist and professor at the school of rehabilitation, faculty of medicine, Université de Sherbrooke. For her part, Dr. Falcone considers that, "We can't know exactly how many patients (suffer from it), because we no longer know how many have actually had COVID-19. So we don't have the true denominator." And as long COVID symptoms are associated with other conditions, “We can miss diagnoses” and therefore have the wrong denominator. The only certainty according to the infectiologist, taken from the INSPQ study, is that, “The risk increases with each reinfection.” It is 13% after one infection, 23% after a second infection and 37% after a third.Widely misunderstood, difficult and time-consuming to diagnose, the post-COVID-19 condition easily slips under the radar of front-line clinicians. Many family doctors consulted by (Medical Post and Pharmacy Practice sister publication) Profession Santé say they've heard nothing more about it and have no cases among their clientele. Yet, statistically speaking, they are bound to have a few. “Either I've been lucky, or I'm no good at catching it,” commented one GP, fatalistically. “As a doctor, there's not much we can do for these patients, it's quite demoralizing.”As a result, sufferers, "experience a lot of medical wandering. Their journey is quite difficult. Their family doctor may believe it more or less. He may also confuse long-term COVID with burn-out or depression. Many of them have had to convince their doctors to refer them to our specialized clinic,” observed Dr. Piché, who is convinced that there is ”still work to be done" in terms of continuing education.In partnership with general practitioners' and specialists' medical federations, the Long COVID Web network will be launching, “a major training program, free of charge for all healthcare professionals,” said Décary. The aim is to share knowledge in order to broaden skills, “in particular to empower family doctors, both in terms of diagnosis and management,” he said, adding that the network of 15 long COVID clinics across Quebec (including those run by Drs. Falcone and Piché) is struggling to keep up with demand. "Currently, 4,000 people are being cared for in all these clinics. Another 2,000 are waiting to be admitted, and we receive over 100 new referrals a month."Specialized clinicsAt a specialized clinic, patients benefit from a thorough assessment of their conditions using a battery of tests. They then enter a personalized rehabilitation process, to reduce their symptoms and make them functional again. With occupational therapy, physiotherapy, psychology and other paramedical services, "We help patients manage their symptoms on a daily basis. Apart from that, we manage their symptoms one by one, depending on whether treatment is available," Dr. Piché said, adding that this multidisciplinary approach can be long and tedious, but generally yields good results.Created three years ago by the government, this network of specialized clinics has developed a fairly unique expertise, said Décary. “We're among the best in the world,” he said, pointing out that, “Elsewhere, many dedicated clinics have closed their doors.” Dr. Falcone agrees. "Quebec has made great efforts. This network sets us apart. We must ensure its continuity and maintain it, because the demand is still there," she said, while worrying the network's funding will not be renewed. The Ministère de la Santé et des Services sociaux (MSSS) reports that, “The pilot project for the network of specialized clinics is in the evaluation phase, with the aim of improving and optimizing the accessibility and fluidity of care and services offered to people with long-onset COVID.” MSSS spokeswoman Marie-Claude Lacasse explains that funding for the network, "was increased in the fall and confirmed for the coming year (2025-2026). For subsequent years, “It will be up to Santé Québec to determine the level of funding. The MSSS has stressed to Santé Québec the importance of prioritizing funding for clinics.”In the meantime, Dr. Falcone hints at, “two very promising large papers” that her research team is about to publish. One concerns blood biomarkers of long-standing COVID, raising the prospect of developing a screening test. The other concerns a new therapeutic target identified in mice. To be continued in the coming weeks.

So many questions: the mysterious, silent epidemic of long COVID

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