Pandemic Levels and Severity
The World Health Organization (WHO) uses a series of six phases of pandemic alert as a system for informing the world of the seriousness of the threat and of the need to launch progressively more intense preparedness activities. The designation of phases, including decisions on when to move from one phase to another, is made by the Director-General of WHO. Each phase of alert coincides with a series of recommended activities to be undertaken by WHO, the international community, governments, and industry. Changes from one phase to another are triggered by several factors, which include the epidemiological behavior of the disease and the characteristics of circulating viruses.
CDC Pandemic Intervals
In March 2008, the federal government issued guidance that introduced the concept of pandemic intervals to describe the progression of an influenza pandemic within communities. The seven CDC pandemic intervals (investigation, recognition, initiation, acceleration, peak transmission, deceleration, and resolution) provide a greater level of specificity than either the World Health Organization’s pandemic periods/phases or the U.S. Government’s pandemic stages.
|
CATEGORY |
CASE FATALITY RATIO (Number of fatalities/total cases |
PROJECTED US DEATHS based on 30% illness rate and 2006 US population |
EXAMPLE |
|
1 |
<0.1% |
<90,000 |
Seasonal influenza |
|
2 |
0.1% - <0.5% |
90,000 - <450,000 |
|
|
3 |
0.5% - <1% |
450,000 - <900,000 |
|
|
4 |
1 – 2% |
900,000 - <1,800,000 |
|
|
5 |
>2% |
>1,800,000 |
Spanish flu of 1918 |
