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Pandemic influenza: medical counter-measures Jo Hofmann, MD Communicable Disease Epidemiology Section Washington State Department of Health July 2006 Influenza - overview • Review the difference between seasonal, avian and pandemic influenza • Update on avian influenza (H5N1) situation in Asia, Europe, Middle East and Africa • Discuss the use of medical interventions to control the spread of pandemic influenza Seasonal, avian or pandemic? • Seasonal influenza Flu that circulates each winter; the virus changes a little from year-to-year • Avian influenza A common infection of birds but virus may also infect other species • Pandemic influenza A widespread, multi-continental outbreak of serious human influenza Caused by a new virus adapted to spread quickly between people How is influenza spread? • Flu virus infects cells in nose and throat • Virus can be spread 24 hours before a person is ill until 5-7 days later • Spread by coughing, sneezing and surfaces contaminated with flu virus Influenza virus subtypes Neuraminidase “N” • Proteins determine characteristics of a virus Which species it infects How deadly it is to host • 2 proteins on surface determine virus subtype Hemagglutinin (“H”) Neuraminidase (“N”) Hemagglutinin “H” • Virus subtypes designated by H and N numbers For example -- H5N1, H3N2 Influenza virus • Infects people, animals and/or birds • Has a simple genetic structure • Likes to share genes and evolves by: RNA genes Mutation Reassortment Areas with confirmed H5N1 influenza in poultry and/or wild birds, 2003-06 As of August 2, 2006 Areas with confirmed H5N1influenza in people, 2003-06 As of August 9, 2006 Total cases 241 Total deaths 141 Avian influenza and pandemics • All 20th century pandemics were caused by a virus closely related to avian influenza • Genetic fingerprint of the 1918-1919 “Spanish” influenza pandemic virus looks “avian-like” but the actual source of the virus is unknown Controlling the spread of influenza Medical counter-measures • List is small Influenza vaccine Antiviral medications Annual process of development, manufacturing, and distribution of influenza vaccine: January- May Annual process of developing, manufacturing and distribution of influenza vaccine: May-October Source: Treanor, J. N Engl J Med 2004;351:2037-2040 Problems with vaccine in a pandemic • Current technology can’t produce vaccine without knowing virus structure Is H5N1 a future pandemic virus? • Vaccine unlikely to be available until months into pandemic • Federal gov’t will probably control distribution of limited vaccine supplies to state and local government agencies Influenza antivirals • Medications to treat or prevent influenza M2 inhibitors - amantidine, rimantidine First approved in 1976 No longer recommended due to resistant influenza strains Neuraminidase inhibitors – oseltamivir, zanamivir (Tamiflu®, Relenza®) First approved in 1999 Antivirals – how they work M2 inhibitors (amantidine, rimantidine) Neuraminidase inhibitors (oseltamivir, zanamivir) Neuraminidase inhibitors • Compared with M2 inhibitors, fewer side effects but more $$$$$$ • Can reduce duration of flu symptoms by 24 hours if taken within the first 48 hours of illness • Can reduce chance of getting flu if exposed • None shown to reduce the complications associated with flu • Seasonal influenza viruses and H5N1 have been identified that are resistant to oseltamivir Problems with antivirals in a pandemic • Pandemic virus could be resistant • Antivirals may not prevent flu complications or deaths • HHS stockpile enough to treat only 25% of the US population • Waiting list for state/local stockpiles orders is long • Current guidelines are for treatment, not prevention of influenza Summary • No magic bullets for the pandemic • We need more research and improved technology for vaccine and antiviral production • We need more information on how well other prevention measures work • A combination of measures will be needed to limit a pandemic The estimated impact of a pandemic on the US and Washington State Moderate (1957/68-like) Severe (1918-like) US Washington US Washington Outpatient care 23–54 million .5 –1.1 million 45 million 943,000 Hospital Care .5–1.2 million 10-24,000 9.9 million 210,009 ICU care 77–180,000 15–3600 1.5 million 31,500 Deaths 117–270,000 23–5400 1.9 million 40,400 Modern Quarantine Honey - will you join me in registering our whereabouts with the appropriate government bureaucracies? Oh, Jim you romantic fool – of course I’ll wear my CDC Division of Global Migration and Quarantine Electronic Locator Ring™