Employers are liable to nonemployees, called third parties, who are injured by negligent employees. These third parties can sue the employer for all the damages allowed in tort litigation. Although the workers’ compensation costs of a communicable disease cannot be ignored, they pale before the costs of third- party liability. Hiring a truck driver with severe heart disease or an alcoholic physician would be negligent, making the company liable to anyone the employee injured. Allowing an employee with infectious tuberculosis to work in a day care center or a demented HIV carrier to be an airplane pilot poses the same risks.

The risk of third-party infections is greatest for foodborne illnesses and highly contagious diseases such as measles that are spread by contact or respiratory transmission. Less infectious respiratory illnesses such as tuberculosis require close or prolonged contact with the infected person. These pose the greatest threat in service industries such as day care centers, where there is close contact between the employees and the customers. Bloodborne illnesses such as hepatitis B virus (HBV) and HIV pose a threat to customers only when there is a chance of exposure to contaminated blood. This is usually thought to be limited to medical care but can happen in any activity where a customer’s skin is pierced. Tattooing, for example, has been implicated in HBV transmission and could transmit HIV.

The most likely third-party victims of workplace-acquired infections are the family members or the unborn children of the worker. When a worker infects a family member with a workplace-acquired infection, the family member may sue the employer. The most serious risks to third parties are those to unborn children. A pregnant worker cannot be excluded from the workplace to protect her fetus. But under current law, if that fetus is injured by a workplace exposure, perhaps to rubella, the employer could be liable for the resulting injuries.

Immunosuppressed family members or other third parties pose difficult legal problems. There is no simple legal rule for determining when a company should be liable for a workplace-related infection to an immunosuppressed worker or third party. Traditional tort law holds that negligent persons take their plaintiffs as they find them: if an employer negligently allows a chicken pox–infected employee to stay in the workplace, the employer would be liable if an immunosuppressed customer contracts chicken pox encephalitis from the employee. Conversely, the doctrine of foreseeability acts as a brake on unlimited liability: if a customer catches a cold from an employee, and then falls off a cliff while sneezing, the employer would not be liable for the fall. However, it is difficult to reconcile jurors’ tendency to hold employers liable for injuries to third parties with the ADA’s strict limitations on the employer’s right to exclude infected workers from the workplace.