Note: Supplementary information is available on the Nature Medicine website. Local public health workers' perceptions toward responding to an influenza pandemic BACKGROUND: Current national preparedness plans require local health departments to play an integral role in responding to an influenza pandemic, a major public health threat that the World Health Organization has described as "inevitable and possibly imminent". To understand local public health workers' perceptions toward pandemic influenza response, we surveyed 308 employees at three health departments in Maryland from March – July 2005, on factors that may influence their ability and willingness to report to duty in such an event. RESULTS: The data suggest that nearly half of the local health department workers are likely not to report to duty during a pandemic. The stated likelihood of reporting to duty was significantly greater for clinical (Multivariate OR: 2.5; CI 1.3–4.7) than technical and support staff, and perception of the importance of one's role in the agency's overall response was the single most influential factor associated with willingness to report (Multivariate OR: 9.5; CI 4.6–19.9). CONCLUSION: The perceived risk among public health workers was shown to be associated with several factors peripheral to the actual hazard of this event. These risk perception modifiers and the knowledge gaps identified serve as barriers to pandemic influenza response and must be specifically addressed to enable effective local public health response to this significant threat. Local health departments are considered the backbone of public health response plans for any and all infectious disease outbreaks. An influenza pandemic is considered increasingly likely, and is now considered one of the most significant and urgent threats to the nation's public health preparedness infrastructure. It has been argued that of the 12 disaster scenarios recently assessed by the U.S. Department of Homeland Security, pandemic influenza is the most likely and perhaps the most deadly [1] . The United States pandemic influenza plan released in November 2005, lays out a critical role for local and state public health agencies during a pandemic, including: providing regular situational updates for providers; providing guidance on infection control measures for healthcare and non-healthcare settings; conducting or facilitating testing and investigation of pandemic influenza cases; and investigating and reporting special pandemic situations [2] . These specified activities would require an extensive prompt response by local health departments. Current contingency plans account for possible personnel shortages due to influenza morbidity, but previous studies have shown that during extreme scenarios, a varying proportion of healthcare workers may be unable or unwilling to report to duty [3] [4] [5] . This may be even truer for health departments, where unlike more "traditional" first responder agencies (such as law enforcement, fire services, and emergency medical services), the capacity and willingness to respond 24/7 to crises is not historically ingrained in the workforces' professional cultures and training. Even in the post-9/11 environment, recent data indicate inconsistent and sometimes slow after-hours response by health departments to urgent events involving communicable disease [6] .