ESR1 and severe acute respiratory syndrome: ♂ mice were more susceptible to SARS-CoV infection compared to ♀ of the same age.The degree of gender bias towards SARS-CoV infection increased with age.Increased susceptibility of ♂mice to SARS-CoV has been associated with elevated virus titers, increased accumulation of inflammatory macrophages and neutrophils in the lungs. Sex differences did not depend on the response of T and B cells. Ovariectomy or treatment of ♀ mice with an estrogen receptor antagonist increased mortality.