2009 influenza pandemic impact on sick leave use in the Veterans Health Administration: framework for a health care provider-based national syndromic surveillance system.

Objective: To determine relations between sick leave use and the 2009 novel influenza A (H1N1) influenza pandemic among clinical and nonclinical staff in the Veterans Health Administration (VHA).
Methods: Aggregate sick leave use for all VHA employees was monitored in near-real time during the 2009 H1N1 influenza pandemic and compared with historical data from 2004 to 2008. The ratio of sick leave use between clinical and nonclinical staff was examined. An autoregressive integrated moving average model was used to assess whether the pandemic had a significant effect on sick leave use.
Results: The H1N1 influenza pandemic was associated with a significant effect on sick leave use in the VHA during the second wave of the pandemic. During this wave, the ratio of clinical to nonclinical sick leave use changed; clinical staff began taking more leave than nonclinical staff for 3 successive 2-week pay periods, with ratio measures of 1.004, 1.018, and 1.011, respectively. Using an autoregressive integrated moving average model with a pulse variable representing the pandemic, there was a significant effect on sick leave use. The average hours of sick leave used per full-time equivalent staff member per month increased by 0.3904 hours (P = .003) for clinical staff and 0.3898 hours (P = .01) for nonclinical staff over previous months during the first month of the second pandemic wave.
Conclusions: Work loss associated with a pandemic is an important indicator of disease activity and may be a more sensitive indicator of emerging strains than deaths. Monitoring sick leave use in near real time in a large national health care system may be an important early indicator of pandemic severity with practical implications that should be considered in addition to more traditional measures of influenza epidemic and pandemic severity.