What We Know Now About Long Covid Syndromes?

ABSTRACT

It is now widely accepted that SARS-CoV-2 infection can affect long-term health and quality of life. Long COVID, a type of post-acute sequelae of SARS-CoV-2 infection (PASC) characterized by persistent unexplained symptoms, has a major impact on the health of many COVID-19 survivors. Although many individuals (up to 30%) experience some limited symptoms in the weeks and months following COVID-19, the prevalence of severe disabling Long COVID is less common (perhaps <5%). Long COVID syndromes are variable and include general (e.g., fatigue) and organ-system specific symptoms (e.g., shortness of breath, palpitations, neurocognitive symptoms), as well as symptoms resembling other medically unexplained syndromes (e.g., myalgic encephalomyelitis/chronic fatigue syndrome, dysautonomia, post-exertional malaise). For reasons not yet understood, female sex is a strong predictor of Long COVID, as is the presence of certain comorbidities, particularly obesity. Mechanisms that might plausibly contribute to Long COVID include irreversible tissue damage associated with acute infection, persistence of SARS-CoV-2 antigen or possibly a viral reservoir, residual or ongoing immune activation and inflammation, reactivation of other latent human viruses, microvascular dysregulation and thrombotic events, microbial translocation, dysbiosis, and autoimmune phenomena. These mechanisms may act in isolation or in combination to drive Long COVID syndromes. Notably, many if not all of these pathways have been implicated as possible mechanisms for the excess rate of cardiovascular disease and other comorbidities in people living with HIV. Industry engagement in Long COVID research is growing, and NIH funding for clinical trials is emerging through programs such as the RECOVER Initiative. As a result, we are entering an era of experimental medicine, in which potential interventions will be used as tools to probe the biology of the disease. This presentation will provide an overview of the proposed biological mechanisms contributing to Long COVID, with a focus on the current state of evidence, human and animal models, and the emerging therapeutic agenda.