Over 40 years ago, Dr. Frank Jobe performed a monumental surgery on left-handed pitcher Tommy John, reconstructing the hurler's ulnar collateral ligament (UCL) with a tendon from John's right, non-throwing wrist (tendons in the ankle or hamstring can also be used). John pitched for another 14 years without missing a start due to an elbow injury and the surgery today has become second-nature in Major League Baseball, often classified as an epidemic.
Epidemic - affecting or tending to affect a disproportionately large number of individuals within a population, community or region at the same time.
Classifying the rash of Tommy John surgeries among a grouping of Major League Baseball pitchers as an epidemic might be a stretch.