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Transcript
PANDEMICS THROUGHOUT HISTORY A pandemic is defined as an unusually high outbreak of a new infectious disease that is spreading through the human population across a large region “pan” – all, “demos” – people According to the World Health Organization (WHO), a pandemic can start when three conditions have been met: emergence of a disease new to a population; agents infect humans, causing serious illness; and agents spread easily and sustainably among humans. Throughout human history there have been numerous pandemics, including the bubonic plague, smallpox, cholera, the Spanish influenza, and most recently HIV Currently we are in the middle of a flu pandemic, with the novel strain of influenza A, H1N1 THE BUBONIC PLAGUE (1347-1352) Also known as the “Black Death” Caused by a bacteria (Yersinia pestis) carried by rats and spread by fleas Infectious agent: Yersinia pestis Reservoir: rats Vector: fleas Kills within 3-7 days if untreated Killed tens of millions across Europe (between ¼ and ½ of the total population) CHOLERA PANDEMIC (1817-1823) A water-bourne bacteria, Vibrio cholerae causes severe diarrhea leading to dehydration and death The first pandemic is characterized by the unprecedented spread of the bacteria throughout Asia, starting at the Lower Ganges River in India Total estimated deaths: 30 000 SPANISH INFLUENZA (1918-1920) A very virulent influenza A subtype H1N1 strain Approximately 1/3 of the world’s population became infected, and anywhere from 50 to 100 million people died worldwide (10-20% of those infected) WW I killed 15 mill., WWII 12 mill., Spanish flu 50 HIV (1981-PRESENT) From 1981 to 2006 AIDS killed more than 25 million people HIV (human immunodeficiency virus) is a retrovirus that can cause AIDS (acquired immunodeficiency syndrome) It is thought to have originated in sub-Saharan Africa HIV is passed through sexual relations, blood or blood products, and mother-to-child transmission THE “SWINE FLU”: H1N1 (APRIL 2009 - ?) Caused by a strain of influenza A, H1N1 Originated as a mixture of swine, avian, and human influenzas The genetic change that allows a virus to “jump species” is called antigenic shift PANDEMICS OF INFLUENZA Recorded human pandemic influenza (early sub-types inferred) H2N2 H2N2 H1N1 H1N1 H3N8 1895 1905 1889 Russian influenza H2N2 1915 Pandemic H1N1 H3N2 1925 1900 Old Hong Kong influenza H3N8 1955 1918 Spanish influenza H1N1 1965 1957 Asian influenza H2N2 1975 1985 H9* H5 H7 1980 Reproduced and adapted (2009) with permission of Dr Masato Tashiro, Director, Center for Influenza Virus Research, National Institute of Infectious Diseases (NIID), Japan. 1965 1975 1985 2005 2010 2009 Pandemic influenza H1N1 1968 Hong Kong influenza H3N2 Recorded new avian influenzas 1955 1995 1999 1997 2003 1996 1995 2002 2005 14 Animated slide: Press space bar 2015 GENETIC ORIGINS OF THE PANDEMIC (H1N1) 2009 VIRUS: VIRAL REASSORTMENT N. American H1N1 (swine/avian/human) Eurasian swine H1N1 PB2 PB1 PA HA NP NA MP NS PB2 PB1 PA HA NP NA MP NS Classical swine, N. American lineage Avian, N. American lineage Human seasonal H3N2 Eurasian swine lineage PB2 PB1 PA HA NP NA MP NS Pandemic (H1N1) 2009, combining swine, avian and human viral components 15 SEASONAL INFLUENZA COMPARED TO PANDEMIC — PROPORTIONS OF TYPES OF CASES Deaths Requiring hospitalisation Clinical symptoms Deaths Requiring hospitalisation Clinical symptoms Asymptomatic Seasonal influenza Asymptomatic Pandemic 18 WHAT WE KNOW SO FAR ABOUT 2009 H1N1 Infection rate for probable and confirmed cases highest in 5−24 year age group. Hospitalisation rate highest in 0−4 year age group, followed by 5−24 year age group. Pregnant women seem particularly at risk Most deaths in 25−64 year age group in people with chronic underlying disease. Adults, especially 60 years and old, may have some degree of preexisting protection There are some predictions that up to 1/3 of the population could become infected… 19 Swine Reality Video What can we do to prepare ourselves for the influenza pandemic?
