Antinucleocapsid IgG and IgM levels together with sC5b-9 levels at admission were associated with respiratory failure at admission (OR 37.7 [CI 1.3 to 1,081.9], P = 0.03 and 33.8 [1.6 to 689.5], P = 0.02, respectively). The gene discussed is CD40LG; the disease is respiratory failure.