Activation of the complement signaling pathway by SARS-CoV infection contributes to the inflammation associated with the pathophysiology of ARDS in severe cases of SARS-CoV infection owing to production of chemoattractant complement C3a, C4, and C5a that contribute to recruitment and activation of neutrophils (Wang et al., 2015; Gralinski et al., 2018). Here, C4A is linked to severe acute respiratory syndrome.