A retrospective examination of concentration of several complement system components (C1Q, C3, C4, and C5) in a cohort of 74 patients with COVID-19 has demonstrated that a high level of expression of nonclassical and lectin complement system activation pathway proteins are linked to negative outcomes of COVID-19, while no analogous connection was found in the case of classical pathway52. The gene discussed is C5; the disease is COVID-19.