摘要：Objectives. We examined the impact of access to paid sick days (PSDs) and stay-at-home behavior on the influenza attack rate in workplaces. Methods. We used an agent-based model of Allegheny County, Pennsylvania, with PSD data from the US Bureau of Labor Statistics, standard influenza epidemic parameters, and the probability of staying home when ill. We compared the influenza attack rate among employees resulting from workplace transmission, focusing on the effects of presenteeism (going to work when ill). Results. In a simulated influenza epidemic (R0 = 1.4), the attack rate among employees owing to workplace transmission was 11.54%. A large proportion (72.00%) of this attack rate resulted from exposure to employees engaging in presenteeism. Universal PSDs reduced workplace infections by 5.86%. Providing 1 or 2 “flu days”—allowing employees with influenza to stay home—reduced workplace infections by 25.33% and 39.22%, respectively. Conclusions. PSDs reduce influenza transmission owing to presenteeism and, hence, the burden of influenza illness in workplaces. Voluntary social distancing measures, such as encouraging sick people to stay home from work, are powerful tools for controlling spread during a contagious disease outbreak. 1 For example, the Centers for Disease Control and Prevention recommends that people with influenza stay home for 24 hours after their fever has resolved. 2 However, not everyone is able to adhere to these recommendations: 42% of workers would not get paid if they stayed home when ill. 3 Willingness to stay home when ill may thus be correlated with access to paid sick days (PSDs). 4–6 In the United States, the Bureau of Labor Statistics reports that 33% of the civilian workforce lacked PSDs in 2010 and that access to PSDs varies depending on workplace size and wage level. Access to PSDs ranged from 53% in workplaces with fewer than 50 employees to 85% in workplaces with 500 or more employees and from 35% in the lowest wage quartile to 87% in the highest quartile. 7 Unequal access to PSDs has been hypothesized to be a source of health disparities in the workplace. Blumenshine et al. 8 proposed a model in 2008 that predicted that social determinants, including inability to take time off from work, could result in unequal levels of illness and death during an influenza pandemic. They hypothesized that staying away from work, if employed as a social distancing policy during a pandemic, was likely to be more difficult for lower-wage workers, as they would be less able to afford losing income. Those who lack PSDs at work may be at higher risk for exposure owing to colleagues not staying home when ill. 9 Presenteeism (going to work or school when ill) leads to further spread of illness by infectious people. Employees who lack PSDs may go to work ill, leading to the spread of infection at work. However, the number of cases expected owing to presenteeism among employees has not previously been examined to our knowledge. In the 2009 H1N1 pandemic, risk of exposure owing to work-related inability to engage in social distancing was significantly related to race and ethnicity. 5 Furthermore, those who reported work-related barriers to social distancing, including lack of access to sick leave, had 1.08 times higher odds ( P < .01) of self-reported influenza-like illness incidence compared with those who were able to engage in social distancing. 4 Recent research has shown that independent of infectious disease spread in the workplace, nonfatal occupational injuries occurred at a higher rate among those without access to PSDs than among those with access to PSDs. 10 Bills under consideration at multiple levels—city and state legislatures—propose providing access to PSDs for employees. 11 Health impact assessments of such PSD policies have hypothesized that they would reduce workplace contagion because ill workers would stay home from work, thus reducing workplace transmission. 9,12,13 These assessments did not account for the nonlinearity in infectious disease spread (each infected person can infect multiple contacts, resulting in an exponential increase in attack rate over time) or the multiple locations in which contacts can occur (households, schools, workplaces, neighborhoods). We examined the impact of access to PSDs on influenza incidence using an agent-based model. In an agent-based model, each individual in a population is represented along with the individual’s social contact networks in households, schools, workplaces, and neighborhoods. Such a model thus permits an examination of transmission patterns in these locations. Infectious disease researchers have used agent-based models extensively to quantify policy impacts, including studies that examine the effects of vaccination and school closure policies during an influenza pandemic on disease outcomes at the overall population level. 14–18 However, previous models have not examined the determinants of behavior but, instead, have usually assumed certain levels of compliance in the population. 14–18 Agent-based modeling remains fairly novel among health behavior researchers studying the impact of access to resources on behavior, disease, and disparities in outcomes. 19–22 We examined the impact of a universal PSD policy and alternative interventions aimed at increasing voluntary social distancing behavior by asking the following questions: How much does presenteeism contribute to disease transmission in the workplace? What proportion of transmission owing to presenteeism is from those without access to PSD? How many cases of influenza would a universal PSD policy prevent? Would alternative interventions to increase the number of days spent at home when ill have an impact on reducing workplace contagion? In keeping with calls for equity-focused health impact assessments, 23,24 we have reported the effect of policies and interventions on health equity in the workplace.
