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Zoonotic Influenza A: H1N1, H5N1 … What does all this mean anyway?

Zoonotic Influenza A: H1N1, H5N1 … What does all this mean anyway?. Shaun Case Public Health Epidemiology PhD Student Walden University PUBH-8165-1 Instructor: Dr. Rebecca Heick Spring Quarter, 2010. Learning Objectives. What is meant by zoonosis, pandemic and epidemic

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Zoonotic Influenza A: H1N1, H5N1 … What does all this mean anyway?

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  1. Zoonotic Influenza A:H1N1, H5N1 … What does all this mean anyway? Shaun Case Public Health Epidemiology PhD Student Walden University PUBH-8165-1 Instructor: Dr. Rebecca Heick Spring Quarter, 2010

  2. Learning Objectives • What is meant by zoonosis, pandemic and epidemic • What is the Influenza virus • What are the types of influenza • How does it infect a cell and replicate • How does Influenza mutate, or change • What is antigenic drift • What is antigenic shift • How does working with animals affect risk

  3. First Things First • Some Definitions • Zoonosis: “disease of animals transmissible to humans under natural conditions”1 • Influenza: “an acute viral infection of the respiratory tract, occurring in isolated cases, epidemics, and pandemics, caused by InfluenzavirusA, B or C … “1 (AKA “The Flu”) • Influenza A: “A genus of viruses of the family Orthomyxoviridae containing the agent of Influenza A”1 (AKA “A type of flu”) • Pandemic: “A widespread epidemic of a disease”1 • Epidemic: “Occurring suddenly in numbers clearly in excess of normal…”1 [1] Saunders (2009). Dorland’s Pocket Medical Dictionary, 28th Ed., Philadelphia: Elsevier-Saunders

  4. Why is this important to discuss • Diseases can be passed between animals and humans and visa-versa1,2,3 • 80% of all infectious diseases known to infect humans are zoonotic4 • 75% of all new human diseases are attributable to diseases originating in animals2 • Cause for concern in the general public [1] Myers K.P., Olsen C.W., Setterquist S.F., et al. (2006). Are swine workers in the United States at increased risk of infection with zoonotic influenza virus? Clinical Infectious Diseases, 42, 14–20 [2] Tomley, F. M. & Shirley, M.W. (2009). Livestock infectious diseases and zoonosis. Philosophical Transactions of the Royal Society B: Biological Sciences, 364, 2637-2642 [3] Gray G.C., Trampel D.W., Roth J.A. (2007). Pandemic influenza planning: Shouldn’t swine and poultry workers be included? Vaccine, 25, 4376-4381 [4] Olmstead A.L. (2009). The First Line of Defense: Inventing the Infrastructure to Combat Animal Diseases. The Journal of Economic History, 69, 327-357

  5. So, what about Influenza? • Found in domesticated animals such as swine, horses, and birds, to name a few1,2,3 • Can also be carried, and spread to other animals, and humans, by feral and wild animals2,4,5 • Some animals are “mixing vessels”1,3 • Influenza A is the primary concern for Zoonosis • Type B is found primarily(though not exclusively) in humans and type C causes generally mild effects in humans6 • Types B and Cmay cause epidemics but have not been known to cause pandemics6 [1] Myers K.P., Olsen C.W., Setterquist S.F., et al. (2006). Are swine workers in the United States at increased risk of infection with zoonotic influenza virus? Clinical Infectious Diseases, 42, 14–20 [2] Spencer, J.L. Guan, J. (2004). Public health implications related to spread of pathogens in manure from livestock and poultry operations. Methods in Molecular Biology, 268, 03-515 [3] Gray G.C., Trampel D.W., Roth J.A. (2007). Pandemic influenza planning: Shouldn’t swine and poultry workers be included? Vaccine, 25, 4376-4381 [4] Tomley, F. M. & Shirley, M.W. (2009). Livestock infectious diseases and zoonosis. Philosophical Transactions of the Royal Society B: Biological Sciences, 364, 2637-2642 [5] Olmstead A.L. (2009). The First Line of Defense: Inventing the Infrastructure to Combat Animal Diseases. The Journal of Economic History, 69, 327-357 [6] CDC (2005). Avian Influenza (Bird Flu). Retrieved on 25 April, 2010 from: http://www.cdc.gov/flu/avian/gen-info/pdf/flu_viruses.pdf

  6. Confused:How does this virus work? • RNA Virus (smaller than a cell)1 • Has no cell wall1 • Invades other cells1 • Alters the infected cell and its DNA1 [1] Webster R., Bean W.J., Gorman O.T., Chambers T.M., Kawoaka Y. (1992) Evolution and Ecology of Influenza A Viruses. Microbiological Review, 56, 152-179

  7. How does this work? (cont.) • Influenza A is made of 8 parts, called segments1 • Those 8 segments are used to make 10 larger components called gene products1 • These determine certain aspects of the virus. • Include products called Hemagglutinin and Neuraminidase, or HA and NA for short. • Commonly recognized in the name of the strain of the virus, such as “H1N1” [1] Webster R., Bean W.J., Gorman O.T., Chambers T.M., Kawoaka Y. (1992) Evolution and Ecology of Influenza A Viruses. Microbiological Review, 56, 152-179

  8. HA and NA? • Control how this virus interacts with the host cell • HA: How well the virus gets along with the host cell1 • Friend or foe: “Do I know you?” • Come on in, make yourself at home… • NA: How well the children of the virus can detach from the inside of the host cell1 to spread to other cells • Allows the children to “leave the nest” • Children move in with someone else, start their own families • Why we classify the strain by the H and N variations. [1] Webster R., Bean W.J., Gorman O.T., Chambers T.M., Kawoaka Y. (1992) Evolution and Ecology of Influenza A Viruses. Microbiological Review, 56, 152-179

  9. What happens next? • Hey, look, it’s a party! (The door is open…with the right HA key…) • Mix with your friends • Decide to stay (Hey, why not, the food is free, and the party never stops?) • Start talking to the other DNA segments • Spread some urban myths • How about a little Antigenic Drift? • Have children,(slow random genetic changes) • Kick the kids out when they’re old enough (replication)

  10. So, what about zoonosis? • Influenza A comes in many varieties1 • All originate in the avian species(birds)1 • Changes in the virus make it able to infect other species, (pigs, horses, humans, etc)1 • Other animals have species specific versions also1 • Mixing of species specific versions causes mutations1 into strange new creatures [1] Webster R., Bean W.J., Gorman O.T., Chambers T.M., Kawoaka Y. (1992) Evolution and Ecology of Influenza A Viruses. Microbiological Review, 56, 152-179

  11. At the party again… • New arrivals from out of town • Move in and settle down • Want a little Antigenic Shift? • Mix with other members of the house • Sometimes have children with others not from their town • Children are a different variety all together... • They like to move to other towns and crash parties

  12. How often does this happen? • Drift and shift happen all the time • Drift is more likely than shift1,2 • Most changes are not viable, (they don’t survive) • Pandemics happen with a regular frequency1,2 • Every 10 to 20 years • Not all are caused by shift, not necessarily zoonotic • Epidemics happen even more frequently, (yearly flu epidemics in humans)1,2 [1] Webster R., Bean W.J., Gorman O.T., Chambers T.M., Kawoaka Y. (1992) Evolution and Ecology of Influenza A Viruses. Microbiological Review, 56, 152-179 [2] Lin J., Andreasen V., Casagrandi R., Levin S. (2003). Traveling waves in a model of influenza A drift. Journal of Theoretical Biology, 222, 437-445

  13. Proximity to Animals • Will living near or working with animals increase my risk of contracting a zoonotic influenza? • Hotly debated topic • We really need more studies • Many studies show a correlation • Some argue those correlations are due to other factors • Correlation does not mean cause

  14. References • Bansal S., Grenfell B., Meyers L.A., (2007). When individual behaviour matters: homogeneous and network models in epidemiology. J R Soc Interface, 4, 879-891 • CDC (2005). Avian Influenza (Bird Flu). Retrieved on 25 April, 2010 from: http://www.cdc.gov/flu/avian/gen-info/pdf/flu_viruses.pdf • Donham K.J., Wing S., Osterberg D., et al. (2007). Community health and socioeconomic issues surrounding concentrated animal feeding operations. Environmental Health Perspectives, 115, 317-20 • Donham K.J. (2000). The concentration of swine production. Effects on swine health, productivity, human health, and the environment. The Veterinary Clinics of North America Food Animal Practice, 16, 559-597 • Gray G.C., McCarthy T., Capuano A.W., et al. (2007). Swine workers and swine influenza virus infections. Emerging Infectious Disease, 13, 1871–1878 • Gray G.C., Trampel D.W., Roth J.A. (2007). Pandemic influenza planning: Shouldn’t swine and poultry workers be included? Vaccine, 25, 4376-4381 • Lin J., Andreasen V., Casagrandi R., Levin S. (2003). Traveling waves in a model of influenza A drift. Journal of Theoretical Biology, 222, 437-445 • Lewis, D.B. (2006). Avian Flu to Human Influenza. Annual Review of Medicine, 57:139-154

  15. References (cont.) • Myers K.P., Olsen C.W., Setterquist S.F., et al. (2006). Are swine workers in the United States at increased risk of infection with zoonotic influenza virus? Clinical Infectious Diseases, 42, 14–20 • Olmstead A.L. (2009). The First Line of Defense: Inventing the Infrastructure to Combat Animal Diseases. The Journal of Economic History, 69, 327-357 • Ramirez A., Capuano A.W., Wellman D.A., et al. (2006). Preventing Zoonotic Influenza Virus Infection. Emerging Infectious Diseases, 12, 997-1000 • Saunders (2009). Dorland’s Pocket Medical Dictionary, 28th Ed., Philadelphia: Elsevier-Saunders • Shinde V., Bridges C., Uyeki T.M., Shu B., Balish A., et al (2009). Triple-Reassortant Swine Influenza A (H1) in Humans in the United States, 2005-2009. New England Journal of Medicine, 361 • Spencer, J.L. Guan, J. (2004). Public health implications related to spread of pathogens in manure from livestock and poultry operations. Methods in Molecular Biology, 268, 03-515 • Tomley, F. M. & Shirley, M.W. (2009). Livestock infectious diseases and zoonosis. Philosophical Transactions of the Royal Society B: Biological Sciences, 364, 2637-2642 • Webster R., Bean W.J., Gorman O.T., Chambers T.M., Kawoaka Y. (1992) Evolution and Ecology of Influenza A Viruses. Microbiological Review, 56, 152-179

  16. Further Reading • CDC: Influenza websites • http://www.cdc.gov/flu/ • http://www.cdc.gov/flu/avian/ • http://www.cdc.gov/h1n1flu/ • http://www.cdc.gov/SocialMedia/Campaigns/H1N1/ • RNA Virus replication • University of South Carolina School of Medicine Virology : http://pathmicro.med.sc.edu/mhunt/RNA-HO.htm • RNA virus mutations and fitness for survival: http://www.ncbi.nlm.nih.gov/pubmed/9343347

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