Pandemic Severity Index
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The Pandemic Severity Index (PSI) is a scale or index created in January 2007 by the United States Centers for Disease Control and Prevention (CDC) designed to mimic the system for indexing the severity of hurricanes (which is the Saffir-Simpson Hurricane Scale for tropical cyclones).[1] If H5N1 evolves into a strain that is easily transmitted person to person (i.e. phase 6) and the U.S. government decides its threat to the U.S. is such that social isolation measures must be taken, then the CDC will select a PSI so local communities can immediately implement the proper social isolation measures.
The University of Minnesota Center for Infectious Disease Research and Policy (CIDRAP) says:
- "Severity level is initially based on case-fatality ratio (CFR), a single criterion that will likely be known even early in a pandemic when small clusters and outbreaks are occurring, the report says. Other measures, such as excess mortality, could be factored in later. Two events would prompt the CDC director to designate a pandemic category: the World Health Organization (WHO) declaring a phase 6 pandemic level and the US government declaring a stage 3, 4, or 5 alert."[1]
The pandemic severity index levels are:
- Category 1, CFR of less than 0.1% (example: seasonal flu)
- Category 2, CFR 0.1% to 0.5% {examples: Asian Flu and Hong Kong Flu)
- Category 3, CFR 0.5% to 1%
- Category 4, CFR 1% to 2%
- Category 5, CFR 2% or higher (example: Spanish flu)[1]
Recommendations for a response to a flu pandemic were based on the history of the last three major flu pandemics, mathematical models, seasonal flu transmission, and input from experts and citizen focus groups.[1]
The report describes these measures for battling a pandemic:
- Isolation and treatment of people who have suspected or confirmed cases of pandemic influenza
- Voluntary home quarantine of household contacts of those with suspected or confirmed pandemic influenza
- Dismissing school classes and closing daycare centers
- Changing work schedules and canceling large public gatherings[1]
CIDRAP says: "For Category 4 and 5 pandemics, the CDC recommends that all four interventions be used and that school classes be suspended for up to 12 weeks. Category 2 or 3 pandemics would warrant voluntary isolation of sick people, though other measures may be added or modified depending on the recommendations of local health authorities; for example, schools could be closed for 4 weeks instead of 12 weeks."[1]
[edit] See also
[edit] Sources and notes
- ^ a b c d e f Roos, Robert; Lisa Schnirring (February 1, 2007). HHS ties pandemic mitigation advice to severity. University of Minnesota Center for Infectious Disease Research and Policy (CIDRAP). Retrieved on 2007-02-03.
[edit] Further reading
- Full text of HHS report
- Feb 1 CDC news release
- Transcript of Feb 1 news conference
- CIDRAP article Experts give qualified praise to new pandemic guidance published February 2,2007
Categories: Pandemics | Epidemiology | Influenza | H5N1
