List of United States Department of Health and Human Services

Pandemic Severity Index

Flu Influenza Virus Avian influenza Flu season Research Vaccine Treatment Genome project H5N1 strain The Pandemic Severity Index (PSI) is a proposed classification scale for reporting the severity of influenza pandemics in the United States. The PSI was accompanied by a set of guidelines intended to help communicate appropriate actions for communities to follow in potential pandemic situations.

Released by the United States Department of Health and Human Services (HHS) on February 1, 2007, the PSI was designed to resemble the Saffir-Simpson Hurricane Scale classification scheme

Development

The PSI was developed by the Centers for Disease Control (CDC) as a new pandemic influenza planning tool for use by states, communities, businesses and schools, as part of a drive to provide more specific community-level prevention measures. Although designed for domestic implementation, the HHS has not ruled out sharing the index and/or guidelines with interested international parties.

The index and guidelines were developed by applying principles of epidemiology to data from the history of the last three major flu pandemics and seasonal flu transmission, mathematical models, and input from experts and citizen focus groups. Many "tried and true" practices were combined together in a more structured manner.

We also realize as we look back through history is what cities did – 44 cities did, is that many of these measures ultimately every city adopted at some point or another, and the difference may be in the timing of using these measures and whether they’re coordinated in an effective way for us to really gain the benefits of them. Dr Martin Cetron, Director of CDC’s Division of Global Migration and Quarantine.

Context

During the onset of a growing pandemic, local communities cannot rely upon widespread availability of antiviral drugs and vaccines (See Influenza research). The goal of the index is to provide guidance as to what measures various organizations can enact that will slow down the progression of a pandemic, easing the burden of stress upon community resources while a definite solutions, like drugs and vaccines, can be brought to bear on the situation. The CDC expects adoption of the PSI will allow early co-ordinated use of community mitigation measures to affect pandemic progression.

Guidelines

The index focuses less on how likely a pandemic is going to get out of control, and more upon how severe the pandemic actually is. The main criterion used to measure pandemic severity will be case-fatality ratio (CFR), the percentage of deaths out of the total reported cases of the disease.

The actual implementation of PSI alerts is expected to occur after the World Health Organisation (WHO) announces phase 6 influenza transmission (human to human) in the United States. This would probably result in immediate announcement of a PSI level 3-4 situation.

The analogy of "category" levels were introduced to provide an understandable connection to hurricane classification schemes, with specific reference to the recent aftermath of Hurricane Katrina. Like the Saffir-Simpson Hurricane Scale, the PSI ranges from 1 to 5. With Category 1 pandemics being most mild (equivalent to seasonal flu) and level 5 being reserved for the most severe "worst-case" scenario pandemics (such as the 1918 Spanish flu.