Burden Estimates for the 2011-2012 Influenza Season
The overall burden of influenza for the 2011-2012 season was an estimated 9 million influenza illnesses, 4 million influenza-associated medical visits, 140,000 influenza-related hospitalizations, and 12,000 flu-associated deaths (Table: Estimated Influenza Disease Burden, by Season — United States, 2010-11 through 2017-18 Influenza Seasons).
| Symptomatic Illnesses | Medical Visits | Hospitalizations | Deaths* | |||||
|---|---|---|---|---|---|---|---|---|
| Age group | Estimate | 95% Cr I | Estimate | 95% Cr I | Estimate | 95% Cr I | Estimate | 95% Cr I |
| 0-4 yrs | 947,030 | (755,712, 1,246,667) | 634,510 | (498,475, 847,571) | 6,602 | (5,268, 8,691) | — | — |
| 5-17 yrs | 1,995,934 | (1,485,293, 3,030,988) | 1,037,886 | (765,690, 1,598,621) | 5,473 | (4,073, 8,311) | — | — |
| 18-49 yrs | 3,478,066 | (2,741,852, 5,221,713) | 1,286,885 | (979,803, 1,988,874) | 19,522 | (15,390, 29,310) | 744 | (237, 2,729) |
| 50-64 yrs | 1,928,610 | (1,554,791, 2,983,510) | 829,302 | (642,931, 1,314,131) | 20,452 | (16,488, 31,639) | 2,328 | (1,392, 6,289) |
| 65+ yrs | 965,981 | (835,332, 1,395,560) | 540,949 | (451,860, 807,903) | 87,816 | (75,939, 126,869) | 9,374 | (6,889, 18,288) |
| All ages | 9,315,621 | (8,673,817, 12,044,892) | 4,329,532 | (4,007,254, 5,565,438) | 139,866 | (130,814, 186,997) | 12,447 | (10,559, 23,491) |
* Estimates of pediatric death are unstable as no deaths in children (aged <18 years) were observed through the Influenza Hospital Surveillance Network (FluSurv-NET) during the 2011-2012 influenza season; however, 17 deaths were reported in children under 5 years old and 20 deaths were reported in children aged 5-17 years through the Influenza-associated Pediatric Mortality Surveillance System.
| Illness rate | Medical visit rate | Hospitalization rate | Mortality rate* | |||||
|---|---|---|---|---|---|---|---|---|
| Age group | Estimate | 95% Cr I | Estimate | 95% Cr I | Estimate | 95% Cr I | Estimate | 95% Cr I |
| 0-4 yrs | 4,697.10 | (3,748.2, 6,183.2) | 3,147.00 | (2,472.3, 4,203.8) | 32.7 | (26.1, 43.1) | — | — |
| 5-17 yrs | 3,711.80 | (2,762.2, 5,636.7) | 1,930.20 | (1,424.0, 2,972.9) | 10.2 | (7.6, 15.5) | — | — |
| 18-49 yrs | 2,564.20 | (2,021.4, 3,849.7) | 948.7 | ( 722.3, 1,466.3) | 14.4 | (11.3, 21.6) | 0.5 | (0.2, 2.0) |
| 50-64 yrs | 3,181.40 | (2,564.7, 4,921.5) | 1,368.00 | (1,060.6, 2,167.7) | 33.7 | (27.2, 52.2) | 3.8 | (2.3, 10.4) |
| 65+ yrs | 2,333.60 | (2,018.0, 3,371.4) | 1,306.80 | (1,091.6, 1,951.7) | 212.1 | (183.5, 306.5) | 22.6 | (16.6, 44.2) |
* Estimates of pediatric death are unstable as no deaths in children (aged <18 years) were observed through the Influenza Hospital Surveillance Network (FluSurv-NET) during the 2011-2012 influenza season; however, 17 deaths were reported in children under 5 years old and 20 deaths were reported in children aged 5-17 years through the Influenza-associated Pediatric Mortality Surveillance System.
