Does a physician need a patient’s written authorization to send a copy of the patient’s medical record to a specialist or other health care provider who will treat the patient?

No. The HIPAA Privacy Rule permits a health care provider to disclose protected health information about an individual, without the individual’s authorization, to another health care provider for that provider’s treatment of the individual. See 45 CFR 164.506 and the definition of “treatment” at 45 CFR 164.501.