As many respiratory viruses are responsible for influenza like symptoms, accurate measures of the disease burden are not available and estimates are generally based on statistical methods. Dena L Schanzer, of the Infectious Disease and Prevention and Control Branch of the Public Health Agency of Canada, and colleagues, sought to estimate absenteeism rates and hours lost due to seasonal influenza and compare these estimates with estimates of absenteeism attributable to the two H1N1 pandemic waves that occurred in 2009.
The researchers extracted key absenteeism variables from Statistics Canada's monthly labor force survey (LFS). Absenteeism and the proportion of hours lost due to own illness or disability were modeled as a function of trend, seasonality and proxy variables for influenza activity from 1998 to 2009.
Hours lost due to the H1N1/09 pandemic strain were elevated compared to seasonal influenza, accounting for a loss of 0.2 percent of potential hours worked annually. In comparison, an estimated 0.08 percent of hours worked annually were lost due to seasonal influenza illnesses. Absenteeism rates due to influenza were estimated at 12 percent per year for seasonal influenza over the 1997/98 to 2008/09 seasons, and 13 percent for the two H1N1/09 pandemic waves. Employees who took time off due to a seasonal influenza infection took an average of 14 hours off. For the pandemic strain, the average absence was 25 hours.
The researchers say their study confirms that absenteeism due to seasonal influenza has typically ranged from 5 percent to 20 percent, with higher rates associated with multiple circulating strains. Absenteeism rates for the 2009 pandemic were similar to those occurring for seasonal influenza. Employees took more time off due to the pandemic strain than was typical for seasonal influenza. Their research was published in BMC Infectious Diseases.
Reference: Schanzer DL, Zheng H and Gilmore J. Statistical estimates of absenteeism attributable to seasonal and pandemic influenza from the Canadian Labour Force Survey. BMC Infectious Diseases 2011, 11:90doi:10.1186/1471-2334-11-90