title: Infection fatality risk of the pandemic A(H1N1)2009 virus in Hong Kong.
abstract: One measure of the severity of a pandemic influenza outbreak at the individual level is the risk of death among people infected by the new virus. However, there are complications in estimating both the numerator and denominator. Regarding the numerator, statistical estimates of the excess deaths associated with influenza virus infections tend to exceed the number of deaths associated with laboratory-confirmed infection. Regarding the denominator, few infections are laboratory confirmed, while differences in case definitions and approaches to case ascertainment can lead to wide variation in case fatality risk estimates. Serological surveillance can be used to estimate the cumulative incidence of infection as a denominator that is more comparable across studies. We estimated that the first wave of the influenza A(H1N1)pdm09 virus in 2009 was associated with approximately 232 (95% confidence interval: 136, 328) excess deaths of all ages in Hong Kong, mainly among the elderly. The point estimates of the risk of death on a per-infection basis increased substantially with age, from below 1 per 100,000 infections in children to 1,099 per 100,000 infections in those 60-69 years of age. Substantial variation in the age-specific infection fatality risk complicates comparison of the severity of different influenza strains.
authors: School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong Special Administrative Region, People's Republic of China.
authors: Jessica Y
authors: JY
authors: Wong
authors: Peng
authors: P
authors: Wu
authors: Hiroshi
authors: H
authors: Nishiura
authors: Edward
authors: E
authors: Goldstein
authors: Eric H Y
authors: EH
authors: Lau
authors: Lin
authors: L
authors: Yang
authors: S K
authors: SK
authors: Chuang
authors: Thomas
authors: T
authors: Tsang
authors: J S Malik
authors: JS
authors: Peiris
authors: Joseph T
authors: JT
authors: Wu
authors: Benjamin J
authors: BJ
authors: Cowling
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000367:Age Factors; D000368:Aged; D002648:Child; D002675:Child, Preschool; D006723:Hong Kong / Q000453:epidemiology; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D053118:Influenza A Virus, H1N1 Subtype / Q000302:isolation & purification; D007251:Influenza, Human / Q000453:epidemiology / Q000401:mortality* / Q000821:virology; D008875:Middle Aged; D058873:Pandemics; D018570:Risk Assessment; D012307:Risk Factors; D015996:Survival Rate