Table 2.
Correlation between influenza epidemic outcomes and timing of interventions in 17 U.S. cities in 1918
| Measure of interventions | Outcome: Excess weekly P&I deaths |
||
|---|---|---|---|
| Peak | Normalized peak | 1918 total | |
| Number of interventions before: | |||
| 10/100,000 CEPID | −0.53, P = 0.03 | −0.53, P = 0.03 | −0.31, P = 0.22 |
| 20/100,000 CEPID | −0.68, P = 0.002 | −0.64, P = 0.005 | −0.52, P = 0.03 |
| 30/100,000 CEPID | −0.51, P = 0.04 | −0.55, P = 0.02 | −0.29, P = 0.27 |
| 40/100,000 CEPID | −0.32, P = 0.21 | −0.40, P = 0.11 | −0.07, P = 0.80 |
| CEPID at time of intervention: | |||
| First | 0.08, P = 0.76 | 0.004, P = 0.87 | 0.07, P = 0.79 |
| Second | 0.54, P = 0.02 | 0.47, P = 0.06 | 0.39, P = 0.12 |
| Third | 0.54, P = 0.02 | 0.52, P = 0.03 | 0.31, P = 0.22 |
| Fourth | 0.66, P = 0.004 | 0.70, P = 0.002 | 0.38, P = 0.13 |
| Fifth | 0.55, P = 0.02 | 0.67, P = 0.003 | 0.27, P = 0.30 |
| Sixth | 0.26, P = 0.31 | 0.44, P = 0.08 | 0.05, P = 0.84 |
| CEPID at time of: | |||
| Closing schools | 0.54, P = 0.02 | 0.63, P = 0.007 | 0.25, P = 0.34 |
| Closing theaters | 0.56, P = 0.02 | 0.72, P = 0.001 | 0.17, P = 0.52 |
| Closing churches | 0.56, P = 0.02 | 0.70, P = 0.002 | 0.17, P = 0.53 |
| Closing dance halls | 0.03, P = 0.90 | 0.04, P = 0.87 | 0.15, P = 0.57 |
| Other closures | 0.33, P = 0.19 | 0.34, P = 0.18 | 0.24, P = 0.35 |
| Making influenza notifiable | 0.01, P = 0.97 | −0.07, P = 0.79 | 0.11, P = 0.67 |
| Bans on public gatherings | 0.46, P = 0.06 | 0.56, P = 0.02 | 0.27, P = 0.30 |
| Imposing case isolation | 0.16, P = 0.53 | 0.14, P = 0.59 | 0.13, P = 0.62 |
| Bans on public funerals | −0.09, P = 0.75 | 0.09, P = 0.72 | −0.41, P = 0.10 |
Three measures of epidemic intensity. Peak weekly excess P&I death rate, normalized peak weekly excess P&I death rate (peak divided by median weekly rate during the study period), and 1918 study period total excess P&I death rate are related to number of interventions before reaching a specified CEPID, CEPID at time when specified numbers of interventions had been imposed, and CEPID at time when specific interventions had been imposed. Spearman rank correlations and associated P values are shown, with bold type for P < 0.05.