The impact of influenza epidemics on hospitalizations.
The traditional method for assessing the severity of influenza seasons is to estimate the associated increase (i.e., excess) in pneumonia and influenza (P&I) mortality. In this study, excess P&I hospitalizations were estimated from National Hospital Discharge Survey Data from 26 influenza seasons (1970-1995). The average seasonal rate of excess P&I hospitalization was 49 (range, 8-102) /100,000 persons, but average rates were twice as high during A(H3N2) influenza seasons as during A(H1N1)/B seasons. Persons aged <65 years had 57% of all influenza-related hospitalizations; however, the average seasonal risk for influenza-related P&I hospitalizations was much higher in the elderly than in persons aged <65 years. The 26 pairs of excess P&I hospitalization and mortality rates were linearly correlated. During the A(H3N2) influenza seasons after the 1968 pandemic, excess P&I hospitalizations declined among persons aged <65 years but not among the elderly. This suggests that influenza-related hospitalizations will increase disproportionately among younger persons in future pandemics.
Simonsen
L
L
Influenza Branch, Division of Viral and Rickettsial Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia 30333, USA.
Fukuda
K
K
Schonberger
L B
LB
Cox
N J
NJ
D000328:Adult; D000367:Age Factors; D000368:Aged; D006760:Hospitalization; D006801:Humans; D007251:Influenza, Human / Q000453:epidemiology* / Q000401:mortality; D008875:Middle Aged; D011014:Pneumonia / Q000453:epidemiology / Q000401:mortality; D012621:Seasons