title: Household transmission of influenza (H1N1-2009) in Japan: age-specificity and reduction of household transmission risk by zanamivir treatment.
abstract: This study investigated household transmission data for influenza (H1N1-2009) in Japan in order to quantify the age-specific risk of infection and estimate the impact of antiviral treatment on the risk of household transmission. Among a total of 1547 households, involving 4609 household contacts, the secondary attack ratio (SAR) was estimated to be 11.4%. School children aged 5 - 18 years dominated the index cases. Age-specific infectiousness and susceptibility were highest among 0 - 4-year olds, with SAR estimated at 19.4% and 29.6%, respectively. Zanamivir treatment within 24 and 24 - 48 h of illness onset in index cases, respectively, reduced the risk of household transmission to 0.57 (95% CI 0.44, 0.73) and 0.58 (95% CI 0.38, 0.86) times that among those receiving the same treatment at > 48 h and those not receiving treatment. The preventive performance of antiviral treatment and prophylaxis should be further examined in randomized controlled trials.
authors.affiliation: PRESTO, Japan Science and Technology Agency, Saitama, Japan. nishiurah@gmail.com
authors.forename: H
authors.initials: H
authors.lastname: Nishiura
authors.forename: H
authors.initials: H
authors.lastname: Oshitani
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000998:Antiviral Agents / Q000494:pharmacology / Q000627:therapeutic use*; D002648:Child; D002675:Child, Preschool; D005191:Family Characteristics; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D053118:Influenza A Virus, H1N1 Subtype / Q000187:drug effects / Q000502:physiology*; D007251:Influenza, Human / Q000188:drug therapy* / Q000517:prevention & control / Q000635:transmission* / Q000821:virology; D007564:Japan; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D016017:Odds Ratio; D012307:Risk Factors; D013997:Time Factors; D055815:Young Adult; D053243:Zanamivir / Q000494:pharmacology / Q000627:therapeutic use*
chemical_list: D000998:Antiviral Agents; D053243:Zanamivir