Pandemic Severity Index
Encyclopedia
The Pandemic Severity Index (PSI) is a proposed classification scale for reporting the severity of influenza pandemic
s 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.
(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:-
s 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 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
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
).
The report recommends four primary measures for slowing down a pandemic:
These actions, when implemented, can have an overall effect of reducing the number of new cases of the disease; but they can carry potentially adverse consequences in terms of community and social disruption. The measures should have the most noticeable impact if implemented uniformly by organizations and governments across the US.
The University of Minnesota
's Center for Infectious Disease Research and Policy
(CIDRAP) reports that the PSI has been "drawing generally high marks from public health officials and others, but they say the plan spells a massive workload for local planners". One MD praised that the PSI were "a big improvement over the previous guidance"; while historical influenza expert and author John M. Barry
was more critical of the PSI, saying not enough emphasis was placed on basic health principles that could have an impact at the community level, adding "I'd feel a lot more comfortable with a lot more research [supporting them]"
During the initial press releases in 2007, the CDC acknowledge that the PSI and the accompanying guidelines were a work in progress and will likely undergo revision in the months following their release.
Influenza pandemic
An influenza pandemic is an epidemic of an influenza virus that spreads on a worldwide scale and infects a large proportion of the human population. In contrast to the regular seasonal epidemics of influenza, these pandemics occur irregularly, with the 1918 Spanish flu the most serious pandemic in...
s in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
. The PSI was accompanied by a set of guidelines intended to help communicate appropriate actions for communities to follow in potential pandemic
Pandemic
A pandemic is an epidemic of infectious disease that is spreading through human populations across a large region; for instance multiple continents, or even worldwide. A widespread endemic disease that is stable in terms of how many people are getting sick from it is not a pandemic...
situations. Released by the United States Department of Health and Human Services
United States Department of Health and Human Services
The United States Department of Health and Human Services is a Cabinet department of the United States government with the goal of protecting the health of all Americans and providing essential human services. Its motto is "Improving the health, safety, and well-being of America"...
(HHS) on February 1, 2007, the PSI was designed to resemble the Saffir-Simpson Hurricane Scale
Saffir-Simpson Hurricane Scale
The Saffir–Simpson Hurricane Scale , or the Saffir–Simpson Hurricane Wind Scale , classifies hurricanes — Western Hemisphere tropical cyclones that exceed the intensities of tropical depressions and tropical storms — into five categories distinguished by the intensities of their sustained winds...
classification scheme.
Development
The PSI was developed by the Centers for Disease Control and PreventionCenters for Disease Control and Prevention
The Centers for Disease Control and Prevention are a United States federal agency under the Department of Health and Human Services headquartered in Druid Hills, unincorporated DeKalb County, Georgia, in Greater Atlanta...
(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
Epidemiology
Epidemiology is the study of health-event, health-characteristic, or health-determinant patterns in a population. It is the cornerstone method of public health research, and helps inform policy decisions and evidence-based medicine by identifying risk factors for disease and targets for preventive...
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:-
Context
During the onset of a growing pandemic, local communities cannot rely upon widespread availability of antiviral drugAntiviral drug
Antiviral drugs are a class of medication used specifically for treating viral infections. Like antibiotics for bacteria, specific antivirals are used for specific viruses...
s 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 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 disease will spread worldwide — that is, become a pandemic — and more upon how severe the epidemic 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
Tropical cyclone scales
Tropical systems are officially ranked on one of several tropical cyclone scales according to their maximum sustained winds and in what oceanic basin they are located...
schemes, with specific reference to the recent aftermath of Hurricane Katrina
Hurricane Katrina
Hurricane Katrina of the 2005 Atlantic hurricane season was a powerful Atlantic hurricane. It is the costliest natural disaster, as well as one of the five deadliest hurricanes, in the history of the United States. Among recorded Atlantic hurricanes, it was the sixth strongest overall...
.
Like the Saffir-Simpson Hurricane Scale
Saffir-Simpson Hurricane Scale
The Saffir–Simpson Hurricane Scale , or the Saffir–Simpson Hurricane Wind Scale , classifies hurricanes — Western Hemisphere tropical cyclones that exceed the intensities of tropical depressions and tropical storms — into five categories distinguished by the intensities of their sustained winds...
, 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
Spanish flu
The 1918 flu pandemic was an influenza pandemic, and the first of the two pandemics involving H1N1 influenza virus . It was an unusually severe and deadly pandemic that spread across the world. Historical and epidemiological data are inadequate to identify the geographic origin...
).
| Category | CFR | example(s) |
|---|---|---|
| 1 | less than 0.1% | Seasonal Flu and Swine Flu H1N1 'Influenza A virus is a subtype of influenza A virus and was the most common cause of human influenza in 2009. Some strains of H1N1 are endemic in humans and cause a small fraction of all influenza-like illness and a small fraction of all seasonal influenza. H1N1 strains caused a few percent of... |
| 2 | 0.1% to 0.5% | Asian Flu and Hong Kong Flu |
| 3 | 0.5% to 1% | |
| 4 | 1% to 2% | |
| 5 | 2% or higher | Spanish flu Spanish flu The 1918 flu pandemic was an influenza pandemic, and the first of the two pandemics involving H1N1 influenza virus . It was an unusually severe and deadly pandemic that spread across the world. Historical and epidemiological data are inadequate to identify the geographic origin... |
The report recommends four primary measures for slowing down a pandemic:
- Isolation and treatment of people who have suspected or confirmed cases of pandemic influenza
- Voluntary home quarantineQuarantineQuarantine is compulsory isolation, typically to contain the spread of something considered dangerous, often but not always disease. The word comes from the Italian quarantena, meaning forty-day period....
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
These actions, when implemented, can have an overall effect of reducing the number of new cases of the disease; but they can carry potentially adverse consequences in terms of community and social disruption. The measures should have the most noticeable impact if implemented uniformly by organizations and governments across the US.
Response
While unveiling the PSI, Dr. Martin Cetron, Director for the Division of Global Migration and Quarantine at the CDC, reported that early feedback to the idea of a pandemic classification scale has been "uniformly positive".The University of Minnesota
University of Minnesota
The University of Minnesota, Twin Cities is a public research university located in Minneapolis and St. Paul, Minnesota, United States. It is the oldest and largest part of the University of Minnesota system and has the fourth-largest main campus student body in the United States, with 52,557...
's Center for Infectious Disease Research and Policy
Center for Infectious Disease Research and Policy
The Center for Infectious Disease Research and Policy is a center within the University of Minnesota that focuses on addressing public health preparedness and emerging infectious disease response...
(CIDRAP) reports that the PSI has been "drawing generally high marks from public health officials and others, but they say the plan spells a massive workload for local planners". One MD praised that the PSI were "a big improvement over the previous guidance"; while historical influenza expert and author John M. Barry
John M. Barry
John M. Barry is an American author and historian, perhaps best known for his books on the Great Mississippi Flood of 1927 and the influenza pandemic of 1918....
was more critical of the PSI, saying not enough emphasis was placed on basic health principles that could have an impact at the community level, adding "I'd feel a lot more comfortable with a lot more research [supporting them]"
During the initial press releases in 2007, the CDC acknowledge that the PSI and the accompanying guidelines were a work in progress and will likely undergo revision in the months following their release.
See also
- 2009 H1N1 influenza outbreak
- Early Warning and Response System
- WHO pandemic phases