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The Threat of Pandemic Influenza

The Threat of Pandemic Influenza. November 11, 2005 Amy Thompson, M.P.Aff. Public Health Response Team, ATCHHSD. Objectives:. At the conclusion of this workshop, participants will be able to… Explain the history of pandemic influenza Explain the threat that pandemic influenza represents

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The Threat of Pandemic Influenza

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  1. The Threat of Pandemic Influenza November 11, 2005 Amy Thompson, M.P.Aff. Public Health Response Team, ATCHHSD

  2. Objectives: At the conclusion of this workshop, participants will be able to… • Explain the history of pandemic influenza • Explain the threat that pandemic influenza represents • Identify personal protective measures to protect against infection • Identify workplace planning needs

  3. Critical prerequisites for pandemic disease: • The infectious agent must be capable of efficient transmission from one person to another; and • Levels of immunity in the general population must be very low.

  4. Few infectious agents are capable of causing pandemic disease: • Smallpox • Plague • Newly emerging, highly transmissible agents • SARS (if it became more highly transmissible) • Influenza

  5. The 1918 Influenza Pandemic • 50 million deaths globally • More deaths in a single year than the worst four years (1347 to 1351) of the Black Death Plague • 1/5 of earth infected • 28% of Americans The Grim Reaper by Louis Raemaekers

  6. The 1918 Influenza Pandemic • 2.5% mortality rate • death rate for 15-34 year age group 20 times higher than usual • 675,000 deaths in US • 10 X the number killed in the WWI

  7. How the US Responded…. Obey the laws And wear the gauze Protect your jaws From Septic Paws

  8. How Public Health Responded… Public Health Recommendations: • Cough & secretion control • Hand washing • Avoid physical exhaustion • Avoid nervous exhaustion • Get enough rest & fresh air • Maintain general hygiene • Eat nourishing foods • Avoid exposure to the cold

  9. Shortages… • Physicians • Nurses • Hospital beds • [Vaccine] • [Antiviral drugs] • [Antibiotics] • Caskets • Morticians • Gravediggers

  10. Lessons learned: • Timely closure of public gathering essential • Hospital capacity and treatment availability crucial

  11. When will the next pandemic occur? • 31 since 1580 • (2004-1580)/31 = ~14 years • Last pandemic was in 1968-69. • 1969 + 14 = 1983 • 2005 – 1983 = 22 • By this calculation, we are 22 years overdue!

  12. 19th Century Pandemics • 1918-19 "Spanish flu" A(H1N1) -- 675,000 deaths, US: 50 million worldwide • 1957-58 "Asian flu" A(H2N2) -- 70,000 deaths, US : 1 million worldwide • 1968-69 "Hong-Kong flu" A(H3N2) -- 34,000 deaths, US : 700,000 worldwide

  13. Influenza A H3N….WHAT? Hemagglutinin (H) Influenza A viruses are subtyped based on two surface antigens Hemagglutinin(H) [cell entry] Neuraminidase(N) [cell escape] Immunity to surface antigens reduces likelihood and severity of infection to same or similar subtypes Neuraminidase (N)

  14. Antigenic Drift vs. Shift Drift - a series of mutations that occur over time and cause a gradual evolution of the virus. Shift - an abrupt change in the hemagglutinin and/or the neuraminidase proteins resulting in a new subtype of the virus.

  15. The Etiologic Agents Influenza A • Humans, swine, horses, ducks, chickens, seals & whales • Antigenic drift and shift • Can cause high mortality in young persons • + Pandemics Influenza B • Humans only • Antigenic drift; no shift • Severe disease usually limited to elderly and high risk • No Pandemics Influenza C • Humans and swine • Antigenic drift; no shift • Mild disease • No seasonality • No pandemics

  16. Hemagglutinin Subtypes of InfluenzaA Virus Subtype Human Swine Horse Bird H1 H2 H3 H4 H5 H6 H7 H8 H9 H10 H11 H12 H13 H14 H15

  17. Neuraminidase Subtypes of Influenza A Virus SubtypeHuman Swine Horse Bird N1 N2 N3 N4 N5 N6 N7 N8 N9

  18. Currently Circulating • Three Influenza A Viruses • H3N2 – the “Hong Kong” flu of 1968-9 • H1N1 – re-emerged in 1977 • H1N2 – reported in February 2002 • One strain of Influenza B

  19. “Avian Influenza” H5N1 • Currently, no efficient transmission to humans • Threat to poultry and related industries

  20. Austin Pandemic Influenza Planning Assumptions • The first wave will have the following effects on the general population in Austin (est. 1,306,627) • 326,657 people will be infected (ill 7 to 10 days) • 13,067 hospitalizations • 5,553 deaths • The second wave will have the following affects on the general population in Austin (est. 1,306,627) • 65,332 people will be infected (ill 7 to 10 days) • 2,614 hospitalizations • 1,111 deaths

  21. ATCHHSD’s Strategy • Daily surveillance (local and global situations) • Annual flu clinics • Preparedness planning (i.e. for mass vaccinations and/ or prophylaxis) • Building “surge” treatment capacity • Educating the public and employers on the importance of PPE and limited social contact

  22. Influenza Transmission and Infection • Spread from person to person by the aerosol route • Most transmitted by droplets formed during coughing or sneezing • Virus replicates exclusively in superficial cells of the respiratory tract • Released by the apical surface of the cell facilitating transmission to the next susceptible host

  23. Clinical Features of Influenza • Sudden onset of symptoms; persist for 7+ days • Incubation period: 1-4 days • Infectious period: 5 days, starting 1 day before symptoms (longer in children) • Varying symptomatology • Fever, headache, cough, sore throat, myalgia, nasal congestion, weakness and loss of appetite • On average, results in 5-6 days restricted activity, 3 days absenteeism • 50% have medically attended illness

  24. During an event: Limit social contacts (avoid handshaking, work from home, avoid public gatherings), and Utilize PPE …according to instructions by local health authorities. Prior to an event: Wash hands Create family preparedness plan and supply kit (including personal protective equipment, PPE) Obtain annual vaccine Lead healthy lifestyle Educate self and family (CDC and ATCHHSD) Recommended PrecautionsFor Individuals

  25. Prior to an event: Plan for pandemic flu (predetermine provision of PPE, tele-work alternatives, and personnel requirements for essential functions) Educate employees and executives (hand washing, PPE, infectious period) Know and train for implementation of the Incident Command System (ICS) Know your organization’s role, if any, in mass vaccination plans During an event: Closely monitor health department advisories Voluntarily implement preventative measures from plan (i.e. PPE, telecommuting, etc.) Respond in a timely manner to official advisories regarding business closures Recommended PrecautionsFor Employers

  26. Questions? Comments? Feedback?

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