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Homeland Security

Scenario 3: Biological Disease Outbreak - Pandemic Influenza

Executive Summary

Casualties At a 15% attack rate: 87,000 fatalities; 300,000 hospitalizations
Infrastructure Damage None
Evacuations/Displaced Persons Isolation of exposed persons
Contamination None
Economic Impact $70 to $160 billion
Potential for Multiple Events Yes, would be worldwide nearly
Recovery Timeline Several months

Scenario Overview:1

General Description -

Influenza pandemics have occurred every 10 to 60 years, with three occurring in the twentieth century (1918, 1957-1958, and 1967-1968). Influenza pandemics occur when there is a notable genetic change (termed genetic shift) in the circulating strain of influenza. Because of this genetic shift, a large portion of the human population is entirely vulnerable to infection from the new pandemic strain.

This scenario hypothetically relates what could happen during the next influenza pandemic without an effective preplanned response. At least twenty-five cases occur first in a small village in south China. Over the next 2 months, outbreaks begin to appear in Hong Kong, Singapore, South Korea, and Japan. Although cases are reported in all age groups, young adults appear to be the most severely affected, and case-fatality rates approach 5%. Several weeks later, the virus appears in four major U.S. cities. By nature, pandemic influenza moves extremely rapidly, and the outbreaks continue.

Timeline/Event Dynamics -

When planning and preparing for the next influenza pandemic, there are two equally important timelines. Due to the rapid spread of the influenza pandemic and the time required to develop, test, produce, and distribute an effective vaccine, the disease will likely arrive in the United States before a "significant" number of people can be vaccinated. The implication of this is that, as part of any pandemic influenza preparation and response plan, there must be a mechanism for allocating the vaccine among the population.

Secondary Hazards/Events -

The greatest secondary hazard will be the problems caused by shortages of medical supplies (e.g., vaccines and antiviral drugs), equipment (e.g., mechanical ventilators), hospital beds, and health care workers. Having a detailed system for allocating resources potentially can reduce such difficulties. This system ideally should be in place well before an influenza pandemic actually occurs. Also of particular concern is the real likelihood that health care systems, particularly hospitals, will be overwhelmed. Another important secondary hazard is the disruption that might occur in society. Institutions, such as schools and workplaces, may close because a large proportion of students or employees are ill. A large array of essential services may be limited because workers are off work due to pandemic influenza. Travel between cities and countries may be sharply reduced.

Key Implications:

Estimates of impact are provided in Table 3-1.

Health Outcomes 15% Gross Attack Rate*
(5th, 95th percentiles)
15% Gross Attack Rate
(5th, 95th percentiles)
Fatalities 87,000
(54,400; 122,200)
207,000
(127,200; 285,300)
Hospitalizations 314,400
(210,400; 417,200)
733,800
(491,000; 973,500)
Outpatient visits 18.1 million
(17.5; 18.7)
42.2 million
(40.8; 43.7)
Self-care ill 21.3 million
(20.6; 21.9)
49.7 million
(48.2; 51.2)
*Percent Gross Attack Rate refers to the percentage of the entire U.S. population that will have a clinical case of influenza.

Note: Assumptions for these estimates are available in the full-text version of this scenario, which also includes an Appendix 3-C that provides graphs and additional estimates.

Table 3-1. Mean estimates (5th, 95th percentiles) of the impact of the next influenza pandemic in the United States without any large-scale and/or effective interventions


Property damage is minimal. Service disruption, however, could be severe due to worker illness. Health care systems will be severely stressed, if not overwhelmed, and first responders are also likely to be severely strained.

Based on the estimates in Table 3-1, the economic impact, in 1995 U.S. dollars, will range from $71 billion (15% gross attack rate) to $166 billion (35% gross attack rate). These estimates include a value for time lost from work but do not include any estimate due to economic disruption or long-term health care costs.

Mission Areas Activated:


Prevention/Deterrence/Protection - Prevention is currently impossible. Protection requires pre-pandemic preparedness, providing more vaccines and conducting more vaccine research and development, antiviral drug stockpiling, and increased surveillance capacity to track illness patterns.

Emergency Assessment/Diagnosis - U.S. influenza surveillance systems will be activated. However, more information is needed regarding attack rate measurements.

Emergency Management/Response - Preparedness plans should contain clear guidelines on setting priorities for the use of scarce resources such as vaccines, drugs, and hospital beds. Federal and state governments have such plans in progress but not all are complete.

Incident/Hazard Mitigation - Success depends on the availability of scarce resources and how well these resources are distributed. Timely, effective public information communication is also important.

Public Protection - Due to late-onset symptoms and the rapid rate at which the disease spreads, evacuation and quarantine are not recommended. Protection will rely on vaccines and antiviral drugs to prevent spread of the disease.

Victim Care - Will rely on the use of antiviral drugs for treatment. Hospitalization and mechanical ventilators will be necessary for many and likely be in short supply. However, at-home care and over-the-counter medications may be helpful for some. A large number of fatalities will likely occur, requiring mortuary and burial services.

Investigation/Apprehension - Investigation is dependent on disease surveillance, although the current system has distinct limitations.

Recovery/Remediation - Not required.


1 Adapted from Patriarcia et al., Pandemic influenza: A planning guide for state and local officials (draft 2.1). Available from http://www.cdc.gov/od/nvpo/pubs/pandemicflu.htm.




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