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									ONONDAGA COUNTY Pandemic Flu Community Planning Guide

last updated: June 2007

Section 1:
A. Background B. Seasonal Flu C. Pandemic Flu

Introduction

D. How is Seasonal Flu Different from Pandemic Flu? E. What is Avian Flu? F. Phases of an Influenza Pandemic G. Pandemic Severity index

A.

Background

Flu pandemics are a significant threat to public health as they have the potential to cause significant illness and death, affect a broad range of the community, and strike not only vulnerable populations, but also the young and healthy. A pandemic is a worldwide epidemic, which constitutes a global health emergency. Flu pandemics have the capacity to cause serious morbidity because the population has little or no immunity to the circulating strain of flu. The 20th century saw three flu pandemics. Although there is no way to predict when the next flu pandemic will occur, health experts such as the Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO), believe that education and outreach are critical to preparing for a pandemic.

B.

Seasonal Flu

Influenza, also called Flu, is a contagious respiratory illness caused by common influenza viruses that are present in our community, primarily on a seasonal basis. Common symptoms include: fever, extreme tiredness, body pain, headache, runny or stuffy nose, dry cough, sore throat, and stomach symptoms such as nausea, vomiting and diarrhea (more common in children than adults). The best way to prevent the flu is by getting a flu vaccination each fall. Onondaga County residents can schedule appointments via the website (www.onflu.net) from mid-October until the end of the flu season, which can last as late as May.

Influenza virus A

Flu is primarily transmitted from person to person by “droplet” spread or direct contact. Droplet spread refers to spray with relatively large, short range droplets produced by sneezing, coughing, talking or singing. These droplets may spray up to three feet and can land directly in eyes or be breathed in through the nose or mouth. Transmission may also occur through direct contact or 1

ONONDAGA COUNTY Pandemic Flu Community Planning Guide

last updated: June 2007

indirect contact with respiratory secretions such as when touching surfaces contaminated with influenza virus and then touching the eyes, nose or mouth. For most adults, the period of communicability is from 24 hours before and up to 3-5 days after symptoms develop. Children and some adults may be infectious for 7 or more days after the onset of symptoms. The incubation period is usually 2 days, but can vary from 1 to 4 days. While a fever can typically last 3-7 days, coughing and muscle ache can last up to two weeks. Influenza viruses are primarily divided into two types: “A” and “B” viruses. The remarkable variation of influenza strains – particularly type A – and their ability to cause annual epidemics of respiratory illness of varying intensity and severity, continue to be the focus of intense investigation. Only type A viruses are known to cause pandemics. Type A viruses are further divided into subtypes based on the specific hemagglutinin (H) and neuraminadase (N) proteins on the virus surface. Hemagglutinin binds to the cell surface to initiate infection. Neuraminidase is involved in the release of virus from infected cells. The emergence of new H or N proteins in the 20th century led to three separate pandemics. For example, the 1918 pandemic resulted from the emergence and spread of the H1N1 virus while the 1968 pandemic was associated with the H3N2 virus. The 1957 pandemic was associated with the emergence and spread of the H2N2 virus, however, this virus subtype stopped circulating in 1968. Pandemics are believed to have occurred for at least 300 years at unpredictable intervals.

C.

Pandemic Flu

A pandemic flu occurs when there is an abrupt and major change in the protein structure of the Influenza A virus resulting in a new subtype. This is known as ‘antigenic shift’. This change may occur in two ways. When two viruses infect the same cell, they may share genetic material (reassortment) and result in a new human virus. Alternatively, a virus may undergo random mutation resulting in an adaptive form more likely to survive in the host. This second type of change may occur during sequential infection of humans and other mammals and lead to a virus more efficiently transmitted amongst humans. Three conditions must be met for a pandemic to start: 1. a new flu virus subtype must emerge for which there is little or no human immunity; 2. it must infect humans and cause illness; and 3. it must spread easily and sustainably (continue without interruption) among humans. In the event of a pandemic, any vaccine or therapeutic drugs are likely to be delayed and/or in short supply. Because of these features, pandemic flu is likely to last several months and affect a large percentage of the national and world population, overloading health care systems, and causing major social and economic disruption. Recent outbreaks of avian flu, that began in Asia in 1996, pose the greatest current threat of a flu pandemic. If the avian flu strains mutate into a virus that is easily transmitted from person-toperson, a pandemic can occur. Such a pandemic would likely originate in Asia and quickly spread across the globe to North America and Onondaga County. This scenario is typical of the patterns exhibited by past pandemics. 2

ONONDAGA COUNTY Pandemic Flu Community Planning Guide

last updated: June 2007

D.

How is Seasonal Flu Different from Pandemic Flu?
Pandemic Flu Occurs rarely (three times in 20th century – last in 1968) No previous exposure; little or no pre-existing immunity Healthy people may be at increased risk for serious complications

Seasonal Flu Outbreaks follow predictable seasonal patterns; occur annually, usually in winter, in temperate climates Usually some immunity built up from previous exposure Healthy adults usually not at risk for serious complications; the very young, the elderly and those with certain underlying health conditions at increased risk for serious complications Health systems can usually meet public and patient needs Vaccine developed based on known flu strains and available for annual flu season Adequate supplies of antivirals are usually available

Health systems may be overwhelmed

Vaccine probably would not be available in the early stages of a pandemic Effective antivirals may be in limited supply because the demand, during a pandemic, could possibly overwhelm current national stockpiles Average U.S. deaths approximately 36,000 / Number of deaths could be quite high (e.g., U.S. year 1918 death toll approximately 675,000) Symptoms: fever, cough, runny nose, Symptoms may be more severe and muscle pain, with deaths often caused by complications more frequent complications such as pneumonia Generally causes modest impact on society May cause major impact on society (e.g., (e.g., some school closing, encouragement widespread restriction on travel, closings of of people who are sick to stay home) schools and businesses, cancellation of large public gatherings) Manageable impact on domestic and world Potential for severe impact on domestic and economies world economies.

E.

What is Avian Influenza?

Avian influenza, or the bird flu, is an infection caused by avian (bird) influenza (flu) viruses. These influenza viruses occur naturally among birds. Wild birds worldwide carry the viruses in their intestines, but usually do not get sick from them. However, avian influenza is very contagious among birds and can make some domesticated birds, including chickens, ducks, and turkeys, very sick and kill them. Infection with avian influenza viruses in domestic poultry causes two main forms of disease. The “low pathogenic”, or less harmful, form may go undetected and usually causes only mild symptoms.

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ONONDAGA COUNTY Pandemic Flu Community Planning Guide

last updated: June 2007

“Avian influenza virus” refers to influenza A viruses found chiefly in birds, but infections with these viruses can occur in humans and other mammals. The risk of human infection from avian influenza is generally low. However, confirmed cases of human infection from several subtypes of avian influenza infection have been reported since 1997. Influenza A (H5N1) virus – also called “H5N1 virus” – is an influenza A virus subtype that occurs mainly in birds, is highly contagious among birds, and can be deadly to them. While H5N1 virus H5N1 does not usually infect humans, some human cases have occurred. Most of the individuals who have contracted the virus in recent years have had direct or close contact with H5N1-infected poultry or H5N1-contaminated surfaces.

F.

Phases of Influenza Pandemic
World Health Organization Pandemic Phases Phase 1 No new influenza virus subtypes have been detected in humans. An influenza virus subtype that has caused human infection may be present in animals. If present in animals, the risk of human infection or disease is considered to be low. Phase 2 No new influenza virus subtypes have been detected in humans. However, a circulating animal influenza virus subtype poses a substantial risk of human disease. Phase 3 Human infection(s) with a new subtype, but no human-to-human spread, or at most, rare instances of spread to a close contact. Phase 4 Small cluster(s) with limited human-to-human transmission but spread is highly localized, suggesting that the virus is not well adapted to humans. Phase 5 Larger cluster(s) but human-to-human spread still localized, suggesting that the virus is becoming increasingly better adapted to humans, but may not yet be fully transmissible. Virus poses a substantial pandemic risk. Phase 6 Pandemic phase: increased and sustained transmission in general population. Return to inter-pandemic period.

Interpandemic Period

Pandemic Alert Period

Pandemic Period Post Pandemic Period

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ONONDAGA COUNTY Pandemic Flu Community Planning Guide

last updated: June 2007

G.

Pandemic Severity Index

The Centers for Disease Control and Prevention (CDC) has developed a Pandemic Severity Index intended to introduce categories of Pandemic intensity, similar to the sytem used to predict hurricane strength. This index (below) will be used to estimate a pandemic’s effect on a community, using the death rate of infected individuals as the measurement of severity (i.e., if 1.5% of individuals infected with the influenza strain experience influenza-related deaths, then the pandemic would be classified as a Category 4). A Category 1 pandemic would be equal to a particularly severe seasonal influenza event, while Category 5 would be akin to the 1918 Spanish flu outbreak which killed over 50 million people worldwide. Please reference Section 5, Part D to understand how the Onondaga County Health Department might implement a public health response based upon the pandemic level decalred.

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