SARS decision rule: who's a suspect?

To the Editor:

We read the article by Wang et al in the January 2004 issue of Annals with interest. However, we have concerns regarding the inclusion criteria used in the study. The Methods state that the population included was those who met the World Health Organization (WHO) definition for suspected severe acute respiratory syndrome (SARS) cases. The WHO criteria for suspected cases at the time of your study included fever, coughing or breathing difficulty, and one of the following: close contact, travel, or residing in an area with recent transmission of SARS within 10 days before the onset of symptoms. We understand that Taiwan became an endemic area just around the time of your study, and thus may not yet have been factored into your inclusion criteria. However, in Table 1, 42% of the patients without SARS did not have a history of travel or exposure, and in Table 3, 73% of the SARS patients and 40% of the non-SARS patients had no history of exposure or travel. Assuming that the inclusion criteria are patients who meet the WHO criteria for suspected cases, how could some of the patients in the study have no history of exposure? We would appreciate your clarification of this seeming incongruity.