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Table 5 Summary of estimates in the US during 2011-2012 and 2012-2013 influenza seasons. Values reported as estimated baseline value and range from variation of recovery rate γ (see section “Sensitivity analysis” for the details of sensitivity analysis)

From: Quantifying the annual incidence and underestimation of seasonal influenza: A modelling approach

Seasonal influenza in the US: 2011-2012 and 2012-2013 influenza seasons

Laboratory-confirmed infections*

27,012

75,772

Estimates generated from Modified CDC-defined ILI in RCT

Season

2011-12

2012-13

Percent of influenza cases captured in surveillance

0.5% (0.41−0.61%)

0.27% (0.2−0.33%)

Expansion factor

200.1 (163.4−243.9)

376.1 (306.7−455.1)

Estimated symptomatic influenza illnesses

5.4×106 (4.4×106−6.9×106)

2.9×107 (2.3×107−3.4×107)

Basic reproduction number

1.19 (1.19−1.19)

1.16 (1.16−1.16)

Estimates generated from respiratory illness associated influenza in RCT

Season

2011-12

2012-13

Percent of influenza cases captured in surveillance

0.1% (0.08−0.12%)

0.09% (0.07−0.11%)

Expansion factor

1030.1 (840.5−1247.0)

1111.4 (906.6−1345.3)

Estimated symptomatic influenza illnesses

2.8×107 (2.3×107−3.4×107)

8.4×107 (6.9×107−1.02×108)

Basic reproduction number

1.20 (1.20−1.20)

1.19 (1.19−1.19)

US CDC estimated symptomatic influenza illnesses

9.3×106

3.4×107

  1. *Indicates infections recorded by the US Center for Disease and Control’s FluView reports [18]