FIGURE 1. Epidemic curves (numbers of cases by date of symptom onset) for severe acute respiratory syndrome (SARS) outbreaks in a) Hong Kong, b) Vietnam, c) Singapore, and d) Canada and the corresponding effective reproduction numbers (R) (numbers of secondary infections generated per case, by date of symptom onset) for e) Hong Kong, f) Vietnam, g) Singapore, and h) Canada, 2003. Markers (white spaces) show mean values; accompanying vertical lines show 95% confidence intervals. The vertical dashed line indicates the issuance of the first global alert against SARS on March 12, 2003; the horizontal solid line indicates the threshold value R = 1, above which an epidemic will spread and below which the epidemic is controlled. Days are counted from January 1, 2003, onwards.