Although some studies have examined professionalism or willingness to work in a hypothetical pandemic or high-risk infection and one study examined the hospital absentee rate during an actual H1N1 pandemic , as far as we know, our survey is the only one that evaluated hospital workers' willingness to work and the influencing factors following an actual pandemic infection. Our study was focused on the factors associated with willingness. The results show that willingness has conflicting aspects. That is, factors that raise motivation do not necessarily lower hesitation: some factors raise both motivation and hesitation.
We found factors were categorised into four types according to their influence on the OR of motivation and hesitation to work. That is, some factors increased the OR of motivation and lowered the OR of hesitation, other factors increased the OR of motivation only, other factors increased the OR of hesitation only, and others increased the OR of both motivation and hesitation. This is important because understanding factors that cause or reduce conflict is necessary to find ways to support professionalism of hospital workers in a high-risk environment.
A limitation of our study is the non-response bias as a result of the 46.7% response rate. However, the total number of subjects was large and their demographics to the population as a whole that did not make noticeable difference.
The most important factors are ones that resolve conflicting emotions and promote willingness, that is, increase motivation and lower hesitation. Above all, the various types of protection that workers receive from the national and local governments and from their hospitals (e.g. protecting them from getting sick and from malpractice suits) needs improvement. The physicians, nurses and others in the ward for H1N1 and the outpatient department for H1N1were provided with protection suits, N95 masks, goggles and antiviral prophylaxes but many of them felt that they were not strongly protected by the national and local government and hospitals. There were no plans about what they should do or how they would be reimbursed in case they became infected and the governments provided no encouraging words to the hospitals. In a study of the use of the antiviral oseltamivir as a prophylactic , 274 employees who worked in high risk places at Kobe City Medical Center General Hospital (KCGH) took oseltamivir from May 16 to May 25, 2009. Only 37% took the medicine for the full ten days. The others stopped taking it for a variety of reasons, including side effects, anxiety about the drug, failure to remember taking it, or because the virulence of H1N1 seemed weak.
The fact that governmental and hospital protection increased motivation and lowered hesitation suggests that positive intervention in these fields will have the strongest impact on reducing non-illness-related absenteeism. Therefore, the protection of hospital workers by governments and hospitals should be emphasized [22–24]. Samuel et al.  suggested that two major factors are involved in instilling employees sense of ethical obligations to treat patients during a crisis. First is an expectation of some reciprocal social obligations. For example, in preparation for epidemics, communities or employers should take all reasonable precautions to prevent illness among health care workers and their families, provide for the care of those who do become ill, reduce or eliminate malpractice threats for those working in high-risk emergency situations and provide reliable compensation for the families of those who die while fulfilling this duty. Second, the duty of physicians should be attenuated but not eliminated, by his or her responsibility in order to prevent them from becoming patients . Work can be attenuated by reducing working time, by restricting the number of patients, by assigning physician to a place with lower workload or by shifting them to jobs with lower risk. In order for workers to fulfil their duties, they need to feel safe. The feeling of safety will be strong when the safety is provided by their organizations. But, in addition to these measurements, there is a need for frequent communication between individual workers and their organization or governments. Encouragement from organizations or governments would also support workers mentally.
In the present study, increased motivation and less hesitation was noted in middle-aged and male workers. Age and gender were also examined in two studies that presented hospital workers with a hypothetical influenza pandemic in the United States  and a hypothetical SARS pandemic in Singapore . These studies found no age or gender difference in the willingness to work, which is inconsistent with our results. This discrepancy may be partly because people in management positions have a strong sense of responsibility, and in our hospitals, many of the management positions are held by males in their 40s and 50s. Another reason for the discrepancy is that our study was based on a real pandemic and the others were based on hypothetical pandemics. As for gender, studies of physicians' burnout have indicated that females feel more stress than males in the workplace [27, 28]. As a result, extra measures should be taken to alleviate the stress of female workers during stressful events, such as by providing childcare services.
Factors that increase motivation only may not always be good because they could result in overfatigue in the long run. Paradoxically, we found that working in a place of high risk and demands for unaccustomed work increased motivation. A Canadian study of senior practitioners with reputations for resilience indicated that making a unique contribution, and receiving privileges and rewards are central to building resilience, although the burden of increased workload was found to lower the level of satisfaction . In view of these results, working in a place of high risk with new work may be considered as a special contribution by hospital workers. Technical/support staffs were especially motivated, perhaps because, in addition to the above reason, they usually had little direct contact with patients and thus had lower perceived levels of risk.
Reducing the factors that cause hesitation only will reduce the barrier to work in high-risk situations. Such stress factors include a lack of knowledge about prevention and protection, the burden of increased quantity of work, the feeling of being avoided by others, and the burden of childcare without childcare facilities. Examples of such measures include work sharing or rotation of duty. Sharing of duties and increasing the number of people who work in high-risk places will provide workers with more concrete knowledge about prevention and protection, lighten their workload, promote a sense of unity and reduce the sense of isolation.
Reducing factors that increase both motivation and hesitation should be given high priority, as these factors can result in the conflict among hospital workers in the long term, although in the short term they may cancel each other out. In the present study, many of the respondents had strong fears of being infected (57.9% of respondents), infecting family (56.1%), feeling of having no choice but to work due to obligation (63.9%) and anxiety about compensation in case of being infected (53.5%). During an infection pandemic, it is to some degree inevitable to feel exhausted and isolated and to worry about becoming infected. But a study said that mitigation strategies that include options for preferential access to either antiviral therapy, protective equipment, or both for the employee as well as his or her immediate family will have the greatest impact . Our hospitals provided all protective measurements listed above to the employee but not to his or her immediate family. The measurement should include protection of employees' family, which might support their motivation and reduce hesitation. In addition, government and hospital managers should develop plans to compensate and treat workers that become infected and to help workers meet their obligations. This would also increase the feeling of protection given by the hospital and the various levels of government.
Although our survey was related to an influenza pandemic, most of the questions used here have generalizability to other high-risk situations. Further studies are needed to test the external validity of our results.