title: Sero-prevalence and incidence of A/H1N1 2009 influenza infection in Scotland in winter 2009-2010.
abstract: BACKGROUND
  Sero-prevalence is a valuable indicator of prevalence and incidence of A/H1N1 2009 infection. However, raw sero-prevalence data must be corrected for background levels of cross-reactivity (i.e. imperfect test specificity) and the effects of immunisation programmes.
  
  
  RESULTS
  We obtained serum samples from a representative sample of 1563 adults resident in Scotland between late October 2009 and April 2010. Based on a microneutralisation assay, we estimate that 44% (95% confidence intervals (CIs): 40-47%) of the adult population of Scotland were sero-positive for A/H1N1 2009 influenza by 1 March 2010. Correcting for background cross-reactivity and for recorded vaccination rates by time and age group, we estimated that 34% (27-42%) were naturally infected with A/H1N1 2009 by 1 March 2010. The central estimate increases to >40% if we allow for imperfect test sensitivity. Over half of these infections are estimated to have occurred during the study period and the incidence of infection in late October 2009 was estimated at 4.3 new infections per 1000 people per day (1.2 to 7.2), falling close to zero by April 2010. The central estimate increases to over 5.0 per 1000 if we allow for imperfect test specificity. The rate of infection was higher for younger adults than older adults. Raw sero-prevalences were significantly higher in more deprived areas (likelihood ratio trend statistic = 4.92,1 df, P = 0.03) but there was no evidence of any difference in vaccination rates.
  
  
  CONCLUSIONS
  We estimate that almost half the adult population of Scotland were sero-positive for A/H1N1 2009 influenza by early 2010 and that the majority of these individuals (except in the oldest age classes) sero-converted as a result of natural infection with A/H1N1 2009. Public health planning should consider the possibility of higher rates of infection with A/H1N1 2009 influenza in more deprived areas.
authors.affiliation: Centre for Infectious Diseases, Ashworth Laboratories, University of Edinburgh, Edinburgh, United Kingdom.
authors.forename: Nigel J
authors.initials: NJ
authors.lastname: McLeish
authors.forename: Peter
authors.initials: P
authors.lastname: Simmonds
authors.forename: Chris
authors.initials: C
authors.lastname: Robertson
authors.forename: Ian
authors.initials: I
authors.lastname: Handel
authors.forename: Mark
authors.initials: M
authors.lastname: McGilchrist
authors.forename: Brajendra K
authors.initials: BK
authors.lastname: Singh
authors.forename: Shona
authors.initials: S
authors.lastname: Kerr
authors.forename: Margo E
authors.initials: ME
authors.lastname: Chase-Topping
authors.forename: Katy
authors.initials: K
authors.lastname: Sinka
authors.forename: Mark
authors.initials: M
authors.lastname: Bronsvoort
authors.forename: David J
authors.initials: DJ
authors.lastname: Porteous
authors.forename: William
authors.initials: W
authors.lastname: Carman
authors.forename: James
authors.initials: J
authors.lastname: McMenamin
authors.forename: Andrew
authors.initials: A
authors.lastname: Leigh-Brown
authors.forename: Mark E J
authors.initials: ME
authors.lastname: Woolhouse
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D003429:Cross Reactions; D005260:Female; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology / Q000472:pathogenicity*; D007251:Influenza, Human / Q000453:epidemiology* / Q000517:prevention & control; D008297:Male; D008875:Middle Aged; D012606:Scotland / Q000453:epidemiology; D012621:Seasons; D016036:Seroepidemiologic Studies; D014611:Vaccination; D055815:Young Adult