title: Estimating time to onset of swine influenza symptoms after initial novel A(H1N1v) viral infection.
abstract: Characterization of the incubation time from infection to onset is important for understanding the natural history of infectious diseases. Attempts to estimate the incubation time distribution for novel A(H1N1v) have been, up to now, based on limited data or peculiar samples. We characterized this distribution for a generic group of symptomatic cases using laboratory-confirmed swine influenza case-information. Estimates of the incubation distribution for the pandemic influenza were derived through parametric time-to-event analyses of data on onset of symptoms and exposure dates, accounting for interval censoring. We estimated a mean of about 1·6-1·7 days with a standard deviation of 2 days for the incubation time distribution in those who became symptomatic after infection with the A(H1N1v) virus strain. Separate analyses for the <15 years and ≥ 15 years age groups showed a significant (P<0·02) difference with a longer mean incubation time in the older age group.
authors.affiliation: MRC Biostatistics Unit, Cambridge, UK.
authors.forename: B D M
authors.initials: BD
authors.lastname: Tom
authors.forename: A J
authors.initials: AJ
authors.lastname: Van Hoek
authors.forename: R
authors.initials: R
authors.lastname: Pebody
authors.forename: J
authors.initials: J
authors.lastname: McMenamin
authors.forename: C
authors.initials: C
authors.lastname: Robertson
authors.forename: M
authors.initials: M
authors.lastname: Catchpole
authors.forename: D
authors.initials: D
authors.lastname: De Angelis
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D055256:Infectious Disease Incubation Period; D053118:Influenza A Virus, H1N1 Subtype; D007251:Influenza, Human / Q000453:epidemiology* / Q000635:transmission*; D008297:Male; D008875:Middle Aged