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Seasonal, Animal and Pandemic Influenza: An Overview

Seasonal, Animal and Pandemic Influenza: An Overview. Learning Objectives. Differentiate between seasonal, avian and pandemic influenza. Overview. Seasonal influenza Animal influenza Pandemic influenza. Photo provided by CDC. Photo provided by National Museum of Health and Medicine.

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Seasonal, Animal and Pandemic Influenza: An Overview

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  1. Seasonal, Animal and Pandemic Influenza: An Overview

  2. Learning Objectives • Differentiate between seasonal, avian and pandemic influenza.

  3. Overview • Seasonal influenza • Animal influenza • Pandemic influenza Photo provided by CDC Photo provided by National Museum of Health and Medicine

  4. Seasonal influenza Photo provided by CDC

  5. Seasonal Influenza • Influenza A and B currently circulating virus subtypes • Minor changes occur in viral genome (antigenic drift) • Spreads easily from person to person • Annual vaccine and anti-virals are principal prevention and control measures • Global public health problem

  6. Impact of Seasonal Influenza • United States1 (annual estimates) • 20- 40 million outpatient visits • 330,000 hospitalizations; 40,000 deaths • US$ 87.1 billion/year for influenza-related costs • England and Wales2 (1989, 1993, 1995) • 192,000-760,00 excess visits to primary care physicians • World-wide (annual estimates)3 • 1million deaths (malaria deaths 1.5-3 million) 1Molinari et al. Vaccine, 2007; 2Douglas Fleming, Pharmaco Econ. 1996;3WHO PAHO, 2007

  7. Excess Mortality in Japan Deaths Excess deaths Threshold Total death Baseline Year

  8. Outbreak of Influenza-Like Illness in Remote Jungle Area in Indonesia, Nov 1995-Feb 1996 • Investigation found significant impact:* • URI episodes doubled to 1,476/100,000 • Pneumonia tripled to 1,000/100,000 • 20% attack rate for 20-50 yr adults • 15% case fatality rate • Influenza A suspected; elevated antibody titres found • Poor nutrition and limited access to health care likely contributed to morbidity and mortality *Based on limited data – no standardized influenza surveillance and mortality reporting Ref: A.L. Corwin et al., Clinical Inf. Dis. 1998

  9. Influenza Outbreaks in Africa • Madagascar, July- August 20021 • 27,000 cases in three months and 800 deaths • ARI attack rate: 67% Ikongo District • 54% of deaths attributed to ARI in children aged < 5years • Highest mortality rate in persons aged ≥ 60 years • Congo, Democratic Republic Nov- Dec 20022 • ILI attack rate: 47.4% Bosobolo District • CFR: 1.5% • CFR higher in: children < 5yrs (3.5%); adults >65 yrs (3.2%) • Both outbreaks attributed to circulating H3N2 virus 1WER 46, 2002; 2WER 13, 2003

  10. Animal Influenza

  11. Animal Influenza • All animal influenza viruses are A subtypes • Wild birds often asymptomatic carriers • Highly contagious in birds • Domesticated birds (chickens, ducks, turkeys) infected by contact with wild birds • Rarely infect humans

  12. H5N1/H1N1 • Was animal or "bird flu" virus of most concern • H5N1 is only one of many different avian viruses • > 300 million poultry deaths due to H5N1 or culling • > 300 cases of human H5N1 • Over > 5000 cases of human H1N1

  13. Pandemic Influenza Photo provided by National Museum of Health and Medicine

  14. Requirements for a Pandemic Global outbreak of disease • New influenza A virus emerges in humans • Minimal or no population immunity • Causes serious illness; high morbidity/mortality • Spreads easily from person to person Photo provided by CDC

  15. Pandemics in the 20th Century 1968: “Hong Kong Flu” 1957: “Asian Flu” 1918: “Spanish Flu” 1 million deaths 1 milliondeaths 20-40 million deaths H3N2 H2N2 H1N1 1920 1940 1960 1980 2000 Adapted from England Dept of Health

  16. Mortality Comparisons

  17. First Pandemic of 21st Century • Reach all parts of the world within 3 months1 • World Bank estimates cost to world economy US$800 billion within a year (SARS cost >US$40 billion) • Deaths: 2 to 7 million (very mild strain)2 1WHO Strategic action plan for pandemic influenza 2006-2007.2006 WHO/CDS/EPR/GIP/2006.2 2WHO Avian influenza: assessing the pandemic threat, 2005 WHO/CDS/2005.29

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