The root cause of the increase of immunizable diseases in the United States is public complacency. After one or more generations of a successful immunization program, the targeted disease becomes rare and no longer frightening. Once the public is no longer concerned about a disease, the financial and political support for disease control measures such as mass immunizations disappears. This creates cohorts of susceptible adults who were neither immunized nor exposed as children, a dangerous situation for employers because many childhood diseases are much more serious in adults. For example, before mumps immunizations, epidemics of mumps would pass through a community regularly, and most of the susceptible population would become immune through having the disease. Complications in these susceptible children were rare, and most children had the disease before reaching puberty. Now, through vaccine failure, lack of exposure to disease or vaccine, and waning immunity, workplace epidemics of mumps can occur. These adult epidemics are dangerous because adults are prone to severe sequelae, with attendant high workers’ compensation costs.

Controlling communicable diseases is complicated by the rise of drug resistance secondary to the misuse of antibiotics. Overprescription by physicians, sharing prescriptions by patients, the use of massive amounts of antibiotics in animal husbandry, and the absence of international controls on antibiotics leads to the evolution of antibiotic-resistant strains of common diseases. Tuberculosis is the best example of the problem. The tuberculosis bacillus is hard to kill and prone to developing drug resistance. The repeated exposure of tuberculosis carriers to ineffective doses of antitubercular drugs dramatically increases the incidence of drug- resistant tuberculosis. There are only a few effective antitubercular drugs. These are all prescription drugs in the United States, but some are available in over-the- counter cough syrup in Mexico.