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Table 1 Numbers of index SARS cases* and non-overlapping contacts† associated with index cases.

From: Quantifying the impact of community quarantine on SARS transmission in Ontario: estimation of secondary case count difference and number needed to quarantine

Quarantine status N of SARS probable and suspect index cases† N of SARS index cases with no community contacts N of SARS index cases with at least one community contact at any level Group total numbers of community contacts (and secondary cases) by level of contact‡§
     All levels Level 1 Level 2A Level 2B Level 3
Not in quarantine at symptom onset 267 89 178 7970 (52) 578 (37) 3186 (14) 1258 (1) 2948 (0)
In quarantine prior to symptom onset 65 39 26 528 (4) 52 (2) 164 (1) 297 (1) 15 (0)
Total 332 128 204 8498 (56) 630 (39) 3483 (15) 1555 (2) 2963 (0)
  1. *Cases of Severe Acute Respiratory Syndrome (SARS) in the Ontario, Canada, 2003 outbreak. Includes all cases with a final disposition of suspect or probable SARS.
  2. † Also considered, in sensitivity analyses only, were an additional 140 individuals who were potential SARS cases at some point during the outbreak and had at least one community contact, but subsequently did not meet criteria for probable or suspect SARS.
  3. ‡ Includes 8,498 community contacts with contact to one SARS case and not a second SARS case within 10 days of exposure to the first within any single 10 day period of exposure.
  4. § Level of contact: 1 = contact for at least 30 minutes within 1 metre; 2A = same room for ≥ 30 minutes; 2B = same room for <30 minutes or same floor, regardless of duration; level 3 = distant contact only - was in same building or large social network.