The primary aim of this paper is to evaluate the claim that presumed consent may constitute grounds for the moral duty to treat. The presumed consent argument is valid, because its conclusion should logically be accepted if its premises are taken into account. To analyze the soundness of the argument we carried out a survey investigating the opinions of HCWs about the occupational risks of infectious diseases. In total, 79.6% of the participants said that they either had some degree of knowledge about the risks when they chose their profession or that they learned of the risks later during their education and training. In other words, one fifth of the participants either lacked adequate knowledge about the occupational risks when they chose their profession or were not sufficiently informed of these risks during their faculty education and training. This means that the assumption stated in Premise 3 may be wrong for an important proportion of health care workers. It seems reasonable to suggest that the words "there is a general understanding" would be misleading if used to characterize a social concept of which the applicability and, indeed, the very existence, are yet to be established by sociological studies.