title: Mortality attributable to seasonal influenza A and B infections in Thailand, 2005-2009: a longitudinal study.
abstract: Influenza epidemiology differs substantially in tropical and temperate zones, but estimates of seasonal influenza mortality in developing countries in the tropics are lacking. We aimed to quantify mortality due to seasonal influenza in Thailand, a tropical middle-income country. Time series of polymerase chain reaction-confirmed influenza infections between 2005 and 2009 were constructed from a sentinel surveillance network. These were combined with influenza-like illness data to derive measures of influenza activity and relationships to mortality by using a Bayesian regression framework. We estimated 6.1 (95% credible interval: 0.5, 12.4) annual deaths per 100,000 population attributable to influenza A and B, predominantly in those aged ≥60 years, with the largest contribution from influenza A(H1N1) in 3 out of 4 years. For A(H3N2), the relationship between influenza activity and mortality varied over time. Influenza was associated with increases in deaths classified as resulting from respiratory disease (posterior probability of positive association, 99.8%), cancer (98.6%), renal disease (98.0%), and liver disease (99.2%). No association with circulatory disease mortality was found. Seasonal influenza infections are associated with substantial mortality in Thailand, but evidence for the strong relationship between influenza activity and circulatory disease mortality reported in temperate countries is lacking.
authors.forename: Ben S
authors.initials: BS
authors.lastname: Cooper
authors.forename: Surachai
authors.initials: S
authors.lastname: Kotirum
authors.forename: Wantanee
authors.initials: W
authors.lastname: Kulpeng
authors.forename: Naiyana
authors.initials: N
authors.lastname: Praditsitthikorn
authors.forename: Malinee
authors.initials: M
authors.lastname: Chittaganpitch
authors.forename: Direk
authors.initials: D
authors.lastname: Limmathurotsakul
authors.forename: Nicholas P J
authors.initials: NP
authors.lastname: Day
authors.forename: Richard
authors.initials: R
authors.lastname: Coker
authors.forename: Yot
authors.initials: Y
authors.lastname: Teerawattananon
authors.forename: Aronrag
authors.initials: A
authors.lastname: Meeyai
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D001499:Bayes Theorem; D002423:Cause of Death; D005260:Female; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype; D053122:Influenza A Virus, H3N2 Subtype; D009980:Influenza A virus; D009981:Influenza B virus; D007251:Influenza, Human / Q000453:epidemiology / Q000401:mortality*; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D012621:Seasons; D018571:Sentinel Surveillance; D013785:Thailand; D055815:Young Adult
keywords: Bayesian regression; burden; developing country; influenza; middle-income country; mortality; seasonal variation; tropics