The number of retail health clinics that have been popping up in places like drugstores for years is expected to double by the end of 2015, according to the consulting firm Accenture. Accenture said in a report released Wednesday that a flood of newly insured patients from the national health care overhaul will help stoke demand for those clinics, which typically treat minor illnesses when a patient doesn't have a doctor or the physician isn't available. The overhaul is expected to expand health insurance coverage to nearly 30 million uninsured people. A big chunk of that growth will start next year when the state-federal Medicaid program for poor and disabled people expands in several states and the government starts offering income-based tax credits to help people buy insurance.