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After being recognized as a unique strain of influenza A virus in April 2009, 2009 H1N1 influenza virus (formerly known as “swine flu”) rapidly swept the globe to become the predominant influenza virus circulating among humans.
Public health planning for controlling such a pandemic includes recommendations for individual activities, pharmaceutical interventions (vaccine, antivirals), non-pharmaceutical interventions, and national and international measures.
The primary goal of these interventions is to reduce (or mitigate) the impact of a pandemic until vaccine is available. This is accomplished by reducing the rate of influenza transmission in communities. The goals of these mitigation efforts are to: delay the peak of the outbreak; lower the peak in order to reduce the demand on healthcare systems and other infrastructure; and reduce the total number of cases.
Non-pharmaceutical community mitigation recommendations are based on observations that influenza is transmitted person-to-person through large respiratory droplets and that children
have a very prominent role in transmitting influenza viruses in most communities. Transmission can occur during close contact or if influenza virus is introduced into eyes, nose or mouth from touching something contaminated. Mathematical modeling of transmission and analysis of patterns from historical influenza pandemics have been used to develop national guidance for non-pharmaceutical interventions. Because no single public health measure is likely sufficient to control influenza transmission, multiple, layered interventions may be used to decrease community transmission of a novel influenza virus. Community mitigation attempts to meet the goals by choosing the timing, duration, and specific combination of interventions.
Interventions
Early in the pandemic, the severity of 2009 H1N1 influenza was unknown. Early reports from Mexico suggested an alarmingly high case fatality rate (>5%) and well-publicized deaths in the United States resulted in similar alarm, initially. Due to concerns about the possible severity of
this new virus, in various states, school closures occurred when small numbers of influenza cases were identified among students.
Based on what is now known about the 2009 H1N1 virus, the Centers for Disease Control and Prevention have developed non-pharmaceutical community mitigation guidance which includes recommendations based on two levels of severity (which are based on proportion of deaths among influenza cases). Should the 2009 H1N1 influenza virus continue to have the morbidity and mortality similar to recent seasonal influenza viruses, only general influenza control measures should be instituted and maintained. Should the severity of illness due to this new virus increase (i.e., develop an increased case fatality ratio) or the attack rate significantly increase, more stringent interventions may need to be instituted in order to reduce community transmission.
Personal activities such as respiratory etiquette (covering coughs and sneezes), hand hygiene (cleaning hands frequently and when contaminated), and staying home when sick are
essential elements for limiting virus transmission. In addition, businesses, employers and schools should be encouraged to help educate their community regarding the importance of these behaviors, to make hand washing facilities readily available, and to promote flexible use of leave time to allow sick workers and those who care for sick children to remain at home. This will reduce virus transmission in the workplace or in schools and child care facilities.
Persons with any contagious respiratory infection are encouraged to stay home in voluntary isolation. For influenza, the recommendation is to stay at home until 24 hours after fever resolves (without the use of medications to control fever). Should the 2009 H1N1 virus become more severe, two community mitigation options would be to extend the period of voluntary isolation to a seven-day minimum or to recommend that anybody who has close contact with a probable case of influenza stays home for an incubation period (voluntary quarantine).
School Closures
The current guidance for the 2009 H1N1 virus with severity similar to seasonal influenza does not include immediate plans to dismiss children from schools or to close child care facilities. Should the severity of this virus change, this guidance will be revisited. CDC has categorized the type of school closure and the expected benefit that can be achieved with each type. Because school closure may occur with little notice, it is important for parents to make a contingency plan for child care when children are home sick or if schools close.
Interventions intended to reduce influenza impact on a community can have secondary consequences that may be adverse to individuals or communities. Staying at home when sick or when family members are sick can affect income or job security and can also reduce the ability to access essential services. It is estimated that 30% of workers in health care, schools and social services are the primary caregiver to children. If schools close and these workers must stay at home, community-wide services may be severely affected as well. Finding alternate child care for ill children may be difficult for some parents and may force suboptimal choices such as leaving children unattended. Children who are dismissed from school may have interruption in their education and meal service, both more consequential for children from low-income families.
All interventions must be enacted with a thoughtful attempt to appropriately balance the benefits of reducing disease transmission with the social disruption caused by mass closures.
Community Social Distancing
Social distancing at work and in the community can reduce influenza transmission. Social distancing in the workplace can include staggered shifts, telecommuting, and conference calls instead of face-to-face meetings. Businesses and workplaces must also plan for the absence of large numbers of their workers due to illness or the need to stay home to care for sick children, by identifying essential services, providing cross-training, and conducting contingency planning.
In case of a worsening severity of the 2009 H1N1 virus, large gatherings such as religious services, sporting events, public entertainment, shopping malls and public transportation may be closed or engineered to reduce transmission. At this time, these interventions seem highly unlikely.
Though the severity of the 2009 H1N1 influenza appears to be similar to seasonal flu, it has a higher attack rate among younger people. As a result, larger numbers of cases are expected with a proportional increase in the numbers of persons with severe morbidity which will stress health care and public health services. In addition, since children will be in school for several months before all high risk persons and school age children can be immunized, non-pharmaceutical interventions will be the primary means for reducing the impact of this pandemic. A team effort between the public, public health partners, schools, businesses, and local, state and federal government will be necessary to select and implement community mitigation activities appropriate to the severity of the pandemic.
Resources
The Department of Health has a 2009 H1N1 influenza website which includes information
for schools, individuals and families, businesses and employers, and community
organizations: http://www.doh.wa.gov/h1n1/default.htmThe Centers for Disease Control and Prevention have a 2009 H1N1 influenza website which includes information for specific audiences (e.g., schools, parents and caregivers, travel industry, businesses and employers, persons with high risk medical conditions) as well as
technical guidance for public health agencies addressing topics such as vaccination, epidemiology and surveillance, clinical guidance, infection control, laboratory testing, and schools): http://www.cdc.gov/h1n1flu/Additional national planning information is available at the federal website http://www.flu.gov
Contributors to this article were Marisa
D'Angeli, MD, MPH and Marcia Goldoft, MD, MPH
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