It is said that there are more female patients, but I think it is a case of gross mis-diagnosis & the disease impacts equally across class, gender, age. The figures range from 2-4 million in USA to 20 million globally, but again it could be way higher as doctors are not taught about viral epidemics or how to diagnose & treat them at med school (shocking). Travel is probably spreading the disease as well as zoonosis (contact with wild animal species).