摘要:The discovery that cases of paralytic polio in 1955 were caused by a single manufacturer of Salk vaccine, the linkage of toxic shock syndrome to tampons in 1979, the identification of the sentinel cases of AIDS on the East and West coasts in the early 1980s, the recognition of West Nile, SARS, and avian flu at the turn of the twenty-first century—were all the result of surveillance systems, through which alert and troubled physicians could communicate with public health officials, thus enabling emerging patterns to be identified. In each instance, such vigilance made it possible to initiate measures that could limit the human toll.