CDC Releases Interim Planning Guidance for Mitigation of Pandemic Influenza
By Eric Toner, M.D. February 7, 2007
On February 1, 2007, the Centers for Disease Control and Prevention (CDC) released its long-awaited disease containment strategy for pandemic influenza: Interim Pre-pandemic Planning Guidance: Community Strategy for Pandemic Influenza Mitigation in the United States--Early, Targeted, Layered Use of Non-Pharmaceutical Interventions. This document is intended for use by states, territories, and local communities in planning for a future pandemic. The goals of the proposed community-based intervention strategy are threefold:
Delay disease transmission and outbreak peak
Decompress peak burden on healthcare infrastructure
Diminish overall cases and health effects.
In comments made at the Seasonal and Pandemic Influenza 2007 conference in Arlington, Virginia, on February 2, 2007, Dr. Julie Gerberding, the Director of the CDC, and Dr. Martin Cetron, the Director of the CDC’s Division of Global Migration and Quarantine, emphasized that the guidance provided in the document was based on the limited scientific evidence that is currently available. Therefore, these interim recommendations will be updated based on new evidence produced by further research. This guidance is intended to be one component of a multi-pronged strategy for pandemic influenza mitigation that also includes use of vaccine and antivirals, both of which are likely to be in limited supply early in a pandemic.
The document introduces a new Pandemic Severity Index (PSI) which uses a 5-point scale that is based on the case fatality ratio (CFR) to categorize the severity of a pandemic, much like the well-known Saffir-Simpson hurricane scale. A category 1 pandemic would have a CFR of < 0.1%; category 3 would have a CFR of 0.5-1.0%; and category 5 would be > 2.0%. To put this in historical context, the 1957 and 1968 pandemics would be category 2 outbreaks, and the 1918 pandemic would be a category 5 outbreak. The guidance proposes a “tool- kit” of 4 non-pharmaceutical interventions (NPI) to be used to mitigate the effects of a pandemic:
Voluntary isolation of the sick at home or in a hospital
Voluntary home quarantine of potentially exposed family members of the sick
Child social distancing, including dismissal of students from schools, closure of childcare programs, and reduced out-of-school social contacts and community mixing
Adult social distancing, including cancellation of large public gatherings and alteration of work environments and schedules.
Based upon the PSI level of a pandemic, some or all of the NPIs would be recommended. For example, in a category 1 pandemic, only isolation of the sick would be recommended. For a category 4 or 5 pandemic, all 4 NPIs would be recommended. The strength and duration of the school closure recommendation also varies with the PSI. For categories 2 and 3, a closure of 4 weeks or less is to be considered. For categories 4 and 5, a 12-week closure is recommended.
The guidance also introduces the terminology of Alert, Standby, and Active to represent the phased escalation of response once a pandemic is recognized. At the Alert level, personnel are notified of their impending activation. At the Standby level, personnel and resources are mobilized and key decision-making processing initiated. At the Activate level, NPIs may be implemented. These 3 levels of action are contingent upon both the PSI of the pandemic and the stage of the pandemic. In a more severe pandemic, the level of action moves more quickly to Activate than in a mild pandemic.
The document recognizes that a great deal of further study is needed to better refine these recommendations. The needed research includes improved surveillance systems that are timely and sensitive to allow for the prompt determination of the PSI level, rapid and reliable diagnostic tools, the feasibility of implementation of the NPIs, the efficacy of the NPIs, and the unintended social consequences of the interventions.
CDC. Interim Pre-pandemic Planning Guidance: Community Strategy for Pandemic Influenza Mitigation in the United States—Early, Targeted, Layered Use of Non-Pharmaceutical Interventions. Available at http://www.pandemicflu.gov/plan/community/community_mitigation.pdf. Accessed February 6, 2007.
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