The morbidity and mortality from communicable diseases is increasing in the United States. Although much of this is secondary to the HIV epidemic, traditional threats such as tuberculosis are also increasing. HIV has also overshadowed new epidemic diseases, such as Lyme disease. Paradoxically, the legal risks of communicable diseases are increasing because the diseases themselves are still relatively rare. If an epidemic afflicts most of the population, it is difficult to link an individual case to a workplace exposure. However, if outbreaks of the disease are infrequent, it will be obvious when an employee’s exposure occurred at work.