NOS2 and viral infectious disease: It has been shown that infection of H5N1 and 1918 viruses induces higher levels of NO in mice compared to the seasonal H1N1 virus and, as a result, they develop more intense pathogenic outcomes, while mice with iNOS deficiency showed reduced morbidity, mortality, and cytokine production in the lungs following H5N1 and 1918 virus infection.