Table 2. Risk of severe influenza-associated outcomes among persons hospitalized with influenza by season and age group.
| Age group | Risk ICU admission, if hospitalized* | Risk of death, if hospitalized* | % deaths in hospital** | Ratio D:H (95% CI)*** | |
|---|---|---|---|---|---|
| <18 years | 15.7% | 0.3% | 49.5% | 0.006 (0.001–0.012) | |
| 2010–11 | 18–64 years | 18.9% | 2.8% | 74.2% | 0.037 (0.029–0.046) |
| 65+ years | 16.1% | 4.7% | 68.7% | 0.068 (0.055–0.081) | |
| <18 years | 19.4% | 0.2% | 43.6% | 0.005 (0.002–0.009) | |
| 2011–12 | 18–64 years | 16.1% | 2.8% | 74.7% | 0.038 (0.023–0.052) |
| 65+ years | 15.9% | 3.4% | 67.5% | 0.050 (0.033–0.068) | |
| <18 years | 18.2% | 0.9% | 46.2% | 0.020 (0.010–0.030) | |
| 2012–13 | 18–64 years | 16.6% | 1.8% | 74.5% | 0.024 (0.018–0.029) |
| 65+ years | 14.7% | 3.6% | 68.1% | 0.053 (0.046–0.060) |
* Calculated from FluSurv-NET surveillance data, all sites
**Among deaths coded as pneumonia, influenza, or acute lower respiratory tract infections in the 2010 and 2011 National Multiple Cause Mortality Files. 2012–13 is an average of the two years with available data.
*** Algebraic combination of the risk of death if hospitalized and the % of deaths that occur during a hospital admission. 95% confidence intervals were calculated by combining the associated binary uncertainty of each parameter.