What chikungunya teaches us about COVID-19

Since December, 2019, the COVID-19 pandemic has generated huge challenges, numerous breakthroughs in research and care, and innovations in public health. 1 year after its emergence, the world is discovering that late clinical consequences of the disease are an increasing problem for patients.

For a substantial proportion of SARS-CoV-2-infected adults, the disease appears biphasic, with long-lasting clinical disorders (so-called long COVID).¹ This post-COVID status might comprise multiple mental or somatic disorders, especially among adults. The prevalence, profile, and determinants of these chronic manifestations remain to be described and understood for appropriate case management. Assessment of clinical disability, quality of life, and fitness for work is required to provide a better view of the real burden of disease and improve our response to the pandemic.

There is a cognitive bias when examining the COVID-19 burden. Considering its mode of transmission (airborne), its clinical influenza-like presentation, and the explosive shape of the epidemic curves, the main comparison for COVID-19 in human history is the influenza pandemic of 1918. Most political and public health leaders are reasoning with the image of influenza in mind. However, by contrast with COVID-19, influenza has no long-term clinical burden.

An acute viral infection with chronic sequelae is not unprecedented. Following our experience with post-chikungunya status, we were struck by the similarities between the long-lasting manifestations after COVID-19 and those after chikungunya virus infection, especially for general and mental disorders, impaired quality of life, and medico-social consequences. Post-chikungunya consequences might account for about 70% of disability-adjusted life-years following a chikungunya outbreak.2, 3 It took about 10 years to describe the post-chikungunya disorders and propose guidelines (still not evidenced-based).⁴ Despite multi-continental outbreaks, there are still fewer than five well designed randomised-controlled trials, and no management strategy exists for patients who have been suffering post-chikungunya consequences for years. One reason for this neglect of the chronicity of chikungunya is a tendency to consider it a simple, short-lived infection like dengue.

A simple comparison of the global burdens of COVID-19, influenza, chikunguna, and dengue fever distinguishes roughly two biphasic infections (chikungunya and COVID-19) and two monophasic ones (influenza and dengue). In a sense, COVID-19 is much closer to chikungunya than to influenza or dengue. We support calls for urgent research on long COVID to avoid having millions of adults with long COVID left behind, with an inestimable social and economic impact. The lessons from post-chikungunya should be learnt.⁵

FS reports being the chief executive officer of RISK&VIR, on a data and safety monitoring board for Valneva, and a senior consultant on chikungunya to PAHO/WHO. HW reports shares in Sanofi. All other authors declare no competing interests.