Table 3 Estimates of the amount of disease attributable to recent transmission calculated using the “n-1” method and retrospective clustering with cases up to two years beforehand, using all cases notified within different time periods during 2007–11
Time period | Number of cases clustered, excluding the first case | Number of cases notified during the study period | Number retrospectively clustered with cases up to 2 years previously | Number of cases with onset more than two years after the start of the study period | % due to recent transmission based on: | |
|---|---|---|---|---|---|---|
“n-1” formula | Retrospective clustering | |||||
2007–11 | 734 | 2159 | 452 | 1329 | 34% (32,36) | 34% (31,37) |
2007–10 | 554 | 1721 | 302 | 891 | 32% (30,34) | 34% (31,37) |
2007–9 | 393 | 1291 | 156 | 461 | 30% (28,33) | 34% (30,38) |