The novel coronavirus tends to affect men more severely than it does women. Though nobody can yet explain the oddity, researchers are hot on the case. It's possible that the sex hormones estrogen and testosterone play a role, according to previous research on respiratory illnesses. Or perhaps it's because the X chromosome (which women have two of, but men have only one) has a larger number of immune-related genes, giving women a more robust immune system to fight off the coronavirus, SARS-CoV-2. Or, maybe the virus is hiding in the testes, which has abundant expression of ACE2 receptors, the portal that allows SARS-CoV-2 into cells.