IL6 and COVID-19: Finally, the top-five of cytokines that most contributed to the observed variation were identified: IL-6, TNF, IL-1β, IL-10, and IL-2 (Fig 5C), and an analysis of the individual average variance across the entire study population showed that the top-ten individuals who were the main contributors to the cytokine profile, six individuals had COVID-19 (recovered, N = 1; long-COVID-19, N = 5) (Fig 5D).