title: Occupational health impact of the 2009 H1N1 flu pandemic: surveillance of sickness absence.
abstract: OBJECTIVE
  Workplace absences due to illness can disrupt usual operations and increase costs for businesses. This study of sickness absence due to influenza and influenza-related illness presents a unique opportunity to characterise and measure the impact of the 2009 (H1N1) pandemic, by comparing trends during the pandemic to those of previous years, and adding this information to that obtained by traditional epidemiological surveillance systems.
  
  
  METHODS
  We compared the numbers of cases of sickness absence due to illness caused by influenza and influenza-related illness in 2007-2009, and in the first 3 months of 2010 in Catalonia (n=811 940) using a time series approach. Trends were examined by economic activity, age and gender. The weekly endemic-epidemic index (EEI) was calculated and its 95% CI obtained with the delta method, with observed and expected cases considered as independent random variables.
  
  
  RESULTS
  Influenza activity peaked earlier in 2009 and yielded more cases than in previous years. Week 46 (in November 2009) had the highest number of new cases resulting in sickness absence (EEI 20.99; 95% CI 9.44 to 46.69). Women and the 'education, health and other social activities' sector were the most affected.
  
  
  CONCLUSIONS
  Results indicate that the new H1N1 pandemic had a significant impact on business, with shifts in the timing of peak incidence, a doubling in the number of cases, and changes in the distribution of cases by economic activity sector and gender. Traditional epidemiological surveillance systems could benefit from the addition of information based on sickness absence data.
authors.affiliation: Department of Experimental and Health Sciences, Center for Research in Occupational Health (CiSAL), Pompeu Fabra University, Barcelona, Spain.
authors.forename: Isabel
authors.initials: I
authors.lastname: Torá-Rocamora
authors.forename: George L
authors.initials: GL
authors.lastname: Delclos
authors.forename: José Miguel
authors.initials: JM
authors.lastname: Martínez
authors.forename: Josefina
authors.initials: J
authors.lastname: Jardí
authors.forename: Constança
authors.initials: C
authors.lastname: Alberti
authors.forename: Rafael
authors.initials: R
authors.lastname: Manzanera
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Yasui
authors.forename: Ramón
authors.initials: R
authors.lastname: Clèries
authors.forename: Aurelio
authors.initials: A
authors.lastname: Tobías
authors.forename: Fernando G
authors.initials: FG
authors.lastname: Benavides
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D015994:Incidence; D053118:Influenza A Virus, H1N1 Subtype; D007251:Influenza, Human / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D058873:Pandemics / Q000706:statistics & numerical data*; D011159:Population Surveillance / Q000379:methods; D012307:Risk Factors; D018582:Sick Leave / Q000706:statistics & numerical data*; D013030:Spain / Q000453:epidemiology