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Transcript
Pandemic Influenza (“Bird Flu”) Valerie Fletcher, M.D. Infectious Diseases Southern Ohio Medical Center September 2006 Introduction Influenza viruses are found in some animal species, and cause a respiratory illness of varying severity. Seasonal influenza affects 5 – 20% of population. 200,000 persons admitted with complications. Influenza results in 36,000 deaths in US annually. The Virus Three strains of influenza virus – A, B, C Influenza A causes illness in humans of all ages and some animals, and is responsible for epidemics and pandemics. Influenza B causes infection in humans and milder epidemics. Influenza C causes a mild illness in children throughout the year. Influenza Virus Nomenclature Neuraminidase Hemagglutinin A/Wisconsin/67/2005 (H3N2) Virus type Geographic origin Strain number Year of Isolation Virus subtype Definitions Seasonal influenza – respiratory viral illness that can be transmitted from person to person and occurs in a cyclic manner. Most people have some immunity. Epidemic influenza – respiratory viral illness in greater numbers than usual, but confined to a single population, community or region. Pandemic influenza – respiratory viral illness due to a new, virulent strain, causing a worldwide outbreak. There is little or no human immunity, and is easily spread from person to person. Features of a Pandemic Influenza Virus New influenza subtype to which there is little or no human immunity. Virus infects humans and causes illness. Spreads easily, and there is sustained spread among humans. 6 Phases of Pandemic Alert – W.H.O. Phase 1: interpandemic phase, low risk of human cases Phase 2: new virus in animals, but no human cases, higher risk of human cases Phase 3: pandemic alert, no or very limited human-to-human transmission. Phase 4: clusters of human cases suggesting increased adaptability of the virus, evidence of increased human-tohuman transmission. Phase 5: larger clusters of human cases over longer period, evidence of significant human-to-human transmission. Phase 6: pandemic, efficient and sustained human-to-human transmission History ~ 35 pandemics recorded in the past 400 years. 3 pandemics in the past century. 1918 pandemic (H1N1) was most lethal in recorded history. > 500,000 people deaths in US as a result of the 1918 Influenza Pandemic (“Spanish flu”). Three Pandemic Waves Influenza and pneumonia mortality, UK - 1918 - 1919 1918 Influenza: The mother of all pandemics. EID Jan 2006 1957 Asian Flu - H2N2 Originated in Far East in Feb 1957 Vaccine production began early May 1957: available in limited supply in August 1957 “Double wave” of illness/death: 1st peak October 1957; 2nd peak Jan/Feb 1958 Number of deaths in US 69,800 (Sept 1957 to March 1958) 1918 1957 1968 ???? Worldwide Spread of H2N2 (“Asian Flu”) in 6 Months Feb-Mar 1957 Apr-May 1957 Jun-Jul-Aug 1957 CDC 69,800 deaths (U.S.) 1968 Hong Kong Flu - H3N2 Four year wave: illness widespread in Dec 1968; same virus returned following 3 flu seasons. Elderly most vulnerable. Number of deaths in US 33,800 (Sept 1968 – March 1969) Impact mitigated: similar to 1957 Asian flu, peaked late in year. 1918 1957 1968 ???? Timeline of Emergence of Influenza A Viruses in Humans Avian Influenza Russian Influenza Asian Influenza Spanish Influenza H7 H5 H1 H3 Hong Kong Influenza H2 H1 1918 H9 H5 1957 1968 1977 1997 1998/9 2003 Avian influenza in Humans Year Strain Country Number of confirmed human cases Number of confirmed human deaths 1997 A/H5N1 Hong Kong 18 6 1999 A/H9N2 Hong Kong 2 0 2003 A/H5N1 Hong Kong 2 1 2003 A/H7N7 Netherlands 89 1 2003 A/H9N2 Hong Kong 1 0 2003 A/H7N2 New York 1 0 2003 A/H7N3 Canada - 0 2003-2006 A/H5N1 Viet Nam, Cambodia, Indonesia, Azerbaijan, China, Djibouti, Egypt, Iraq, Turkey, and Thailand 247 144 September 2006 Nations with confirmed cases of H5N1 Avian Influenza (July2006) WHO Cumulative Number of Confirmed Human Cases of Avian Influenza A/(H5N1) Reported to WHO 2003 Country 2004 2005 2006 Total cases deaths cases deaths cases deaths cases deaths cases deaths Azerbaijan 0 0 0 0 0 0 8 5 8 5 Cambodia 0 0 0 0 4 4 2 2 6 6 China 1 1 0 0 8 5 12 8 21 14 Djibouti 0 0 0 0 0 0 1 0 1 0 Egypt 0 0 0 0 0 0 14 6 14 6 Indonesia 0 0 0 0 19 12 46 37 65 49 Iraq 0 0 0 0 0 0 3 2 3 2 Thailand 0 0 17 12 5 2 2 2 24 16 Turkey 0 0 0 0 0 0 12 4 12 4 Viet Nam 3 3 29 20 61 19 0 0 93 42 Total 4 4 46 32 97 42 100 66 247 144 Total number of cases includes number of deaths. WHO reports only laboratory-confirmed cases. September 19, 2006 Transmission Inhalation of droplets containing infectious material. Direct contact. Indirect contact. Human to human transmission Animal to human transmission. Clinical Features Fever Chills Cough Sore throat Body aches Headache Runny or stuffy nose Nausea, vomiting, diarrhea Complications Pneumonia Exacerbation of cardiac or lung diseases Death Persons at greatest risk of complications Persons > 65 yrs Infants Persons with chronic disease Pregnant women Nursing home residents Treatment Antiviral agents Supportive care – eg respiratory support, nutrition, hydration Prevention Influenza vaccine Antiviral agents Isolation Quarantine Definitions Isolation – separation of an infected person from others during period of disease communicability, in such a way that prevents, as far as possible, the direct or indirect transfer of infectious agent to susceptible persons. Quarantine – separation and restriction of movement of people who have been exposed to infectious agent, are potentially infectious, but not yet showing signs of illness. May be voluntary or mandatory. Infection Control Isolation – private room or cohort with other patients with same illness. N 95 masks for caretaker entering room. Surgical masks for patients leaving isolation room if still infectious. Handwashing (or alcohol gel), gloves, gown, eye protection. Surgical masks Goggles N95 mask Handwashing Hands are wet with running water. Lather with soap for at least 15 seconds. Rinse hand with running water. Dry hands with disposable towel. Turn off tap with disposable paper towel. Place disposable towel in appropriate container. Waterless alcohol-based hand rub or rinse Approx. 3 ml of product taken from dispenser and rubbed on dry skin for about 30 sec until alcohol evaporates. Effective only on areas in contact with rub or rinse. Does not remove soil or organic material. Does not replace handwashing with soap and water if hands are visibly soiled. Contains 60 -70% alcohol. Contains a moisturizer to prevent drying of skin. DHHS Pandemic Preparedness – Five Priorities Monitor disease spread to support rapid response. Developing vaccines and vaccine production capacity. Stockpiling antivirals and other countermeasures. Coordinating federal, state and local preparation. Enhancing outreach and communication planning. Pandemic Planning Update II, DHHS Secretary Michael Leavitt, 6/06 Pandemic Planning Update, DHHS Secretary Michael Leavitt, 03/06 Vaccine Development Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec (WHO/CDC) surveillance select strains prepare reassortants standardize antigen WHO/CDC/FDA CDC/FDA FDA FDA assign potency review/license FDA manufacturers formulate/test/package clinic vaccinate CDC Pandemic vaccine Vaccine to target H5. Production will start at the time the pandemic strain is detected. Production may take up to 6 months. Initial vaccine shortage expected. 2 doses may be needed. Priority Groups for Pandemic Vaccine - DHHS 1A 1B 1C 1D Healthcare workers involved in direct patient care; vaccine and antiviral manufacturing personnel (9 million). Highest risk group (26 million). Household contacts of children < 6 months and severely immunocompromised patients, pregnant women (11 mil). Key government leaders and critical public health pandemic responders (150,000). 2 High risk group, public safety and transportation workers. 3 Other key government health decision makers, mortuary workers. 4 Healthy 2 – 64 year old persons not in the other groups (180 million). Antivirals Oseltamivir (Tamiflu®) and Zanamivir (Relenza®). Used for prophylaxis and treatment. Supply limited – national stockpile. Need for prioritization. Unlikely to affect the course of the pandemic. Other control measures Educate to encourage self-diagnosis. Public health information – risk avoidance, hygiene practices Defer or limit travel Seasonal influenza vaccine Impact of Pandemic Influenza Onset and scope of pandemic unpredictable. Much depends on virulence of the virus and human immunity. Availability of effective drugs and vaccines uncertain. Health services will be overwhelmed. Surveillance and early diagnosis important in curtailing spread. Impact of Pandemic Influenza Estimated attack rate 15% - 35% Projected 314,000 – 733,000 hospitalizations Projected 89,000 – 207,000 deaths Meltzer et al, EID 1988 Comparison of 1918 Influenza Pandemic and projections for 2000 YEAR 1918 2000 World Population 1.8 Billion 5.9 Billion Primary mode of transportation Troopships, railroad Commercial aircraft, automobiles Time for virus to circle the globe 4 months 4 days Estimated deaths worldwide 20+ million 60 million? B. Wallace MD, P Smith MD. NYS DOH 2005 Social disruption Civil unrest Schools closed No transportation Absenteeism Disruption of essential and non-essential services Economic impact Preparing for a pandemic Surveillance Training/Education Volunteer Build a kit with essentials Plan to care for self and others for ~ 72h without assistance Preparing for a pandemic Stockpile water and nonperishable food First aid kit Flashlight Radio (battery-operated) Medication Tools Clothing Money Preparing for a pandemic Personal items Pet supplies Money Gas Identify resources/Contact information Support system During a Pandemic Wash hands or use alcohol hand cleanser frequently. Cover your cough. Proper disposal of used tissue and other potentially contaminated material. Social distancing – stay home if sick and avoid people who are sick. Stay informed pandemicflu.gov cdc.gov 1-800-CDC-INFO (1-800-232-4636 or 1-888-232-6348) who.org Media Local authorities Pandemic influenza today H5N1 is a likely candidate to cause a pandemic, however, it is not expected to do so in its current form. Rare cases of human to human transmission. No cases of sustained transmission in humans. No cases of H5N1 detected in birds or humans in North America.