All the books on Reiki till now do not say so. Sensei Usui was not a christian. Recent information from those in Japan have given us a clearer picture of sensei Usui's biography. There are persons everywhere who never knew Reiki and never got attuned to it by any Reiki master, but effectively heal the sick using their palms. Even they do mass healing.
Every human being is capable of healing.
There are those that can do it naturally, or that have had a spiritual experience that has given them this gift. Reiki is only one way of receiving the ability to heal. Native American Medicine men and women have some healing techniques that are done with the hands and that are like Reiki. God has given all peoples of the world that which they need to heal themselves and others. Sacred Path Reiki.