America's prescription drug epidemic reaches deep into the medical community. Across the country, more than 100,000 doctors, nurses, technicians and other health professionals struggle with abuse or addiction, mostly involving narcotics such as oxycodone and fentanyl. Their knowledge and access make their problems especially hard to detect. Yet the risks they pose — to the public and to themselves — are enormous. A single addicted health care worker who resorts to "drug diversion," the official term for stealing drugs, can endanger thousands. Nearly 8,000 people in eight states needed hepatitis tests after David Kwiatkowski, an itinerant hospital technician, was caught injecting himself with patients' pain medicine and refilling the syringes with saline.