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Pandemic Influenza Overview

Pandemic Influenza Overview. 衛福部 疾病管制署 中區傳染病防治醫療網 王任賢 指揮官. Outline. What is influenza? What is an influenza pandemic? History of influenza pandemics Control measures. Influenza. Respiratory infection

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Pandemic Influenza Overview

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  1. Pandemic InfluenzaOverview 衛福部 疾病管制署 中區傳染病防治醫療網 王任賢 指揮官

  2. Outline • What is influenza? • What is an influenza pandemic? • History of influenza pandemics • Control measures

  3. Influenza • Respiratory infection • Transmission:contact with respiratory secretions from an infected person who is coughing and sneezing • Incubation period:1 to 5 days from exposure to onset of symptoms • Communicability:Maximum 1-2 days before to 4-5 days after onset of symptoms • Timing:Peak usually occurs December through March in North America

  4. Clinical Presentation of Influenza

  5. Influenza Symptoms • Rapid onset of: • Fever • Chills • Body aches • Sore throat • Non-productive cough • Runny nose • Headache

  6. Signs & Symptoms Influenza Cold Onset Sudden Gradual Fever Characteristic, high (over Rare 101F); lasting 3 to 4 days Cough Nonproductive; can Hacking become severe Headache Prominent Rare Myalgia (aches and pains) Usual; often severe Slight Fatigue; weakness Can last up to 2 to 3 weeks Very mild Extreme exhaustion Early and prominent Never Chest discomfort CommonMild to moderate Stuffy nose Sometimes Common Sneezing Sometimes Usual Sore throat SometimesCommon Influenza vs Cold Symptoms Adapted from the National Institute of Allergy and Infectious Diseases.

  7. Classic Signs & Symptoms of Influenza • Rapid onset of symptoms • Fever, usually over 100F • Nonproductive cough • Headache • Myalgia • Chills and/or sweats • Sore throat • Potentially severe, persistent malaise • Substernal soreness, photophobia & ocular problems Cox NJ, Fukuda K. Infect Dis Clin North Am. 1998;12:28.

  8. Onset of Influenza A in Volunteer -1 0 1 2 3 4 5 6 7 8 23 Days After Inoculation 100 Temp °F 99 97 Illness Headache, Malaise, Myalgia Nasal Obstruction and Discharge,Throat Pain, Cough Adapted from Mandell GL, Bennett JE, Dolin R, eds. Mandell, Douglas and Bennett’s Principles and Practice of Infectious Disease. 5th ed. 2000:1831.

  9. Shedding of Influenza A in Volunteer Virus Sheddinglog10 TCID50 per mL nasal wash Day Adapted from Mandell GL, Bennett JE, Dolin R, eds. Mandell, Douglas and Bennett’s Principles andPractice of Infectious Disease. 4th ed. 1995:1554.

  10. Influenza is a serious illness • Annual deaths: 36,000* • Hospitalizations: >200,000* * Average annual estimates during the 1990’s • Who is at greatest risk for serious complications? • persons 65 and older • persons with chronic diseases • infants • pregnant women • nursing home residents

  11. Complications of influenza • Viral and bacterial pneumonia • Myositis/myoglobulinemia & renal failure • Myocarditis • CNS manifestations

  12. Respiratory complications of influenza • Primary viral pneumonia • Secondary bacterial pneumonia • Combined viral-bacterial pneumonia • Exacerbation of COPD • Exacerbation of asthma

  13. Viral Pneumonia Bacterial Pneumonia 2nd to Flu Patients more at risk – Children and adults with – Age >65 yrs cardiovascular disease, chronic – Patients with chronicpulmonary, pulmonary and metabolic disease cardiac and metabolic or other and hemoglobinopathies disease – Pregnant women – Young adults (H1N1) – Immunosuppressed patients, such as those with cancer, HIV/AIDS or organ transplants Clinical history Rapid progression from classic flu Improvement after classic flu symptoms symptoms, then worsening Sputum Gram stain Predominantly normal flora – no Pneumococcus significant evidence of Staphylococcus pathogenic bacteria Haemophilus influenzae Moraxella catarrhalis Chest x-ray Bilateral findings Consolidation WBC Leukocytosis with shift to left Leukocytosis with shift to left DDx of Viral vs Bacterial Pneumonia • Adapted from Treanor JJ. In: Mandell, Douglas, and Bennett’s Principles and Practice of Infectious Diseases. 5th ed. 2000:1834-1835; Piedra PA. Semin Respir Infect. 1995;10:218.

  14. Bacterial Etiology The marked changes that may occur in the etiology of bacterial pneumonia during an influenza outbreak are shown in the graph above. Note that the percentage of patients with staphylococcal pneumonia more than doubles during an influenza outbreak (and is more than 2.5 times as high if staphylococci found with other organisms are included), while the proportion attributable to pneumococcal infection decreases. Hospital Practice December 1976

  15. Influenza Types • Type A • Epidemics and pandemics • Animals and humans • All ages • Type B • Milder epidemics • Humans only • Primarily affects children

  16. Influenza Virus Composition Type of nuclear material Neuraminidase Hemagglutinin A/Beijing/32/92 (H3N2) Virus type Geographic origin Strain number Year of Isolation Virus subtype

  17. Influenza Antigenic Changes Structure of hemagglutinin (H) and neuraminidase (N) periodically change: • Drift:Minor change, same subtype • In 1997, A/Wuhan/359/95 (H3N2) virus was dominant • A/Sydney/5/97 (H3N2) appeared in late 1997 and became the dominant virus in 1998 • Shift: Major change, new subtype • H2N2 circulated in 1957-67 • H3N2 appeared in 1968 and replaced H2N2 • Pandemic potential

  18. Timeline of Emergence of Influenza A Viruses in Humans Avian Influenza H9 H7 Russian Influenza H5 H5 H1 Asian Influenza H3 Spanish Influenza H2 Hong Kong Influenza H1 1918 1957 1968 1977 1997 2003 1998/9

  19. Pandemic influenza: definition • Global outbreak with: • Novel virus, all or most susceptible • Transmissible from person to person • Wide geographic spread

  20. Impact of Past Influenza Pandemics/Antigenic Shifts

  21. Pandemic influenza: 2nd waves • 1957: second wave began 3 months after peak of the first wave • 1968: second wave began 12 months after peak of the first wave

  22. Next pandemic: impact Attack rate ranging from 15% to 35%: • Deaths: 89,000 - 207,000 • Hospitalizations: 314,000 - 733,000 Source: Meltzer et al. EID 1999;5:659-71

  23. Estimated hospitalizations due to influenza pandemic 95th percentile Mean 5th percentile Source: Meltzer et al. EID 1999;5:659-71

  24. Estimated deaths due to influenza pandemic 95th percentile Mean 5th percentile Source: Meltzer et al. EID 1999;5:659-71

  25. The 1918 Influenza Pandemic

  26. America’s Forgotten Pandemicby Alfred Crosby “The social and medical importance of the 1918-1919 influenza pandemic cannot be overemphasized. It is generally believed that about half of the 2 billion people living on earth in 1918 became infected. At least 20 million people died. In the Unites states, 20 million flu cases were counted and about half a million people died. It is impossible to imagine the social misery and dislocation implicit in these dry statistics.”

  27. America’s deaths from influenza were greater than the number of U.S. servicemen killed in any war Thousands Civil WWI 1918-19 WWII Korean Vietnam War Influenza War War

  28. Spanish Influenza • Slowed to a trickle the delivery of American troops on the Western front. • 43,000 deaths in US armed forces. • Slow down and eventual failure of the last German offensive (spring and summer 1918) attributed to influenza.

  29. Infectious Disease Mortality, United States--20th Century Armstrong, et al. JAMA 1999;281:61-66.

  30. Worldwide Spread in 6 Months Spread of H2N2 Influenza in 1957“Asian Flu” Feb-Mar 1957Apr-May 1957Jun-Jul-Aug 1957 69,800 deaths (U.S.)

  31. “Asian Flu” Timeline February 1957 • Outbreak in Guizhou Province, China April-May 1957 • Worldwide alert • Vaccine production begins October 1957 • Peak epidemic, follows school openings December 1957 • 34 million vaccine doses delivered • Much vaccine unused January-February 1958 • Second wave (mostly elderly)

  32. Close calls: avian influenza transmitted to humans • 1997: H5N1 in Hong Kong 18 hospitalizations and 6 deaths • 1999: H9N2 in Hong Kong 2 hospitalizations • 2003: • H5N1 in China 2 hospitalizations, 1 death • H7N7 in the Netherlands 80 cases, 1 death (eye infections, some resp. symptoms)

  33. Avian Influenza Poultry Outbreaks, Asia, 2003-04

  34. Avian Influenza Poultry Outbreaks, Asia, 2003-04 • Historically unprecedented scale of outbreak in poultry • Human cases reported from Vietnam and Thailand (as of 1/21/05: 52 cases; 39 deaths) • No sustained person-to-person transmission identified • Duration of the outbreak creates potential for genetic change that could result in person-to-person transmission

  35. “The pandemic clock is ticking, we just don’t know what time it is” E. Marcuse

  36. Influenza Control: vaccine • Cornerstone of prevention • Annual production cycle ensures availability by late summer/early summer

  37. surveillance select strains prepare reassortants standardize antigen assign potency review/license formulate/test/package vaccinate Vaccine Development Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec WHO/CDC) WHO/CDC/FDA CDC/FDA FDA FDA FDA manufacturers clinic

  38. Pandemic Vaccine • Annual vaccine is trivalent (3 strains), pandemic vaccine will be monovalent. • Production using current technologies would likely take 4-5 months  may not be available before 1st pandemic wave • There will be vaccine shortages initially • 2 doses may be necessary to ensure immunity

  39. Influenza control: antiviral medications • Uses • Prophylaxis • Treatment • Issues • Limited supply • Need for prioritization (among risk groups and prophylaxis versus treatment) • Unlikely to markedly affect course of pandemic

  40. Influenza control: infection control • influenza isolation precautions* • Private room or with other influenza patient • Negative air pressure room, or placed with other suspected influenza cases in area of hospital with independent air supply • Masks for HCW entering room • Standard droplet precautions (hand washing, gloves, gown and eye protection) * 1994 Guidelines for Prevention of Nosocomial Pneumonia

  41. Infection control, cont’d • Feasibility of these measures in a pandemic setting is questionable, priorities should include: • Droplet transmission precautions (use of masks and hand hygiene) • Cohorting of influenza-infected patients

  42. Influenza control: other control measures • Education to encourage prompt self-diagnosis • Public health information (risks, risk avoidance, advice on universal hygiene behavior) • Hand hygiene • Face masks for symptomatic persons • School closures (?) • Deferring travel to involved areas

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