Mao BMC Public Health 2011, 11:522 http://www.biomedcentral.com/1471-2458/11/522 As people spend more time at home during the extended weekend, it is not surprising that the foci of infection gradually move from workplaces to homes (Figure 7). This also explains why the highest intensity of infections often occurs within the CBD (Figure 4 and 6). With a household density of 1,189.30/km2, the CBD has a much higher concentration of residents than the transition zone (879.30/km2) and suburb (21.30/km2). The dense contact network woven by concentrated resi- dents retained the CBD relatively insensitive to the weekend-extension strategies. In this case, the CBD could be further targeted by household prophylaxis or household quarantine strategies, as complementary interventions. A vaccination program prioritizing CBD residents would also be a wise preparation for weekend- extension strategies. In addition to the land use patterns, the travel beha- vior of individuals is another key factor for disease dis- persion [13]. This explains why the three-day continuous extension strategy is the most effective to confine the spatial spread of seasonal flu. The long weekend period greatly reduces the travel between homes and workplaces, which is a major component of individual daily activities. Many infectious individuals stay home for 5 consecutive days, “using up” the infec- tious period of influenza virus. When these individuals go back to work, they are no longer infectious and can- not infect their co-workers, thereby limiting the long- distance dispersion of influenza. From perspectives of psychology, ethics and law, the weekend-extension strategy may involve milder issues than other non-pharmaceutical strategies, such as the case isolation or household quarantine. It has been widely reported that many non-pharmaceutical strate- gies, particularly for long duration, can cause loneliness, emotional detachment and infringement of individual rights, such as the freedom of movement [24]. Differ- ently, the weekend-extension strategy only causes short- term social separation, and allows people to move freely to anywhere they want during the extended weekend. Many ethical and legal issues therefore could be possibly mitigated or avoided. The socio-economic loss from work/school absentee- ism is a potential problem for implementing weekend extension strategies. One solution is to encourage peo- ple to work at home during the extended weekend, complete business transactions through telecommunica- tion, and take courses online. In such a manner, the face-to-face contacts for infection are reduced, while long-term interruptions on socio-economy could be minimized. If the long-distance working and learning are not feasible for certain occupations, an alternative is to grant these groups of people a higher priority for receiving pharmaceutical interventions. Page 9 of 10 Conclusions This research is the first attempt to consider the week- end effect on influenza control and prevention, and starts a new direction for designing mitigation strategies. The effectiveness of weekend-extension strategies depends on the length and pattern of extensions, as well as the compliance of businesses. The simulation results suggest that the extension of regular weekend by more than two days can significantly mitigate seasonal flu epi- demics. For pandemic flu, the weekend-extension strate- gies are not effective alone, but would be useful complements to pharmaceutical strategies. Like other non-pharmaceutical strategies, the week- end-extension strategy could be a feasible measure for countries with limited health resources, because no stockpiles of vaccines and antiviral drugs are needed. Although influenza is taken as an example in this research, it is believed that the concept of weekend extensions can also help fight other emerging infec- tious diseases that are poorly understood and unpre- pared for, such as new strains of influenza, SARS (Severe acute respiratory syndrome), and Ebola. With the advance in telecommunication technologies and the shift of working styles from workplace to home, the weekend-extension strategy may have long-term containment benefits for this class of diseases, and would be a wise option for public health planners in the near future. Acknowledgements The author is thankful for the valuable comments from the editor and two reviewers. Publication of this article was funded by the University of Florida Open-Access Publishing Fund. Authors’ contributions LM conceived and designed the work, performed all coding and simulation, carried out all analyses, and is the author of the manuscript. Competing interests The author declares no competing interests. Received: 9 March 2011 Accepted: 30 June 2011 Published: 30 June 2011 References 1. Key Facts About Seasonal Influenza (Flu). [http://www.cdc.gov/flu/about/ disease/index.htm]. 2. Updated CDC Estimates of 2009 H1N1 Influenza Cases, Hospitalizations and Deaths in the United States, April 2009 - April 10, 2010. [http:// www.cdc.gov/h1n1flu/estimates_2009_h1n1.htm]. 3. Smith DJ: Predictability and Preparedness in Influenza Control. Science 2006, 312(5772):392-394. 4. Fiore AE, Shay DK, Haber P, Iskander J, Uyeki T, Mootrey G, Bresee JS, Cox NJ: Prevention and control of influenza: Recommendations of the Advisory Committee on Immunization Practices (ACIP). Morbidity and Mortality Weekly Report 2007, 56:1-54. 5. Kelso JK, Milne GJ, Kelly H: Simulation suggests that rapid activation of social distancing can arrest epidemic development due to a novel strain of influenza. BMC Public Health 2009, 9(1):117. 6. Ferguson NM, Keeling MJ, Edmunds WJ, Gani R, Grenfell BT, Anderson RM, Leach S: Planning for smallpox outbreaks. Nature 2003, 425(6959):681-685.