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HLTA01 Influenza.docx

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University of Toronto Scarborough
Health Studies
Sandy Romain

HLTA01 Influenza 19/03/2013 6:12:00 AM Influenza  Seasonal Influenza o Rates increase in colder seasons due to more people indoors o U.S. between 1976-2006 flu-associated deaths range from 3,000 to 49,000 per year o 90% of deaths occur in those aged >65 yrs (risk group)  should always get flu shot  Epidemic/Pandemic Influenza o Surges in influenza cases/deaths caused by a highly virulent and infectious strain  Can show diff peeks o Can be differences in risk groups and/or seasonality History  Limited lasting immunity for influenza o Measles- life long once contracted and need large population density o Influenza- no immunity, small population  Associated with domestication of animals  First evidence in 1400s and 1500s o None in new world due to no domestic animals  First European epidemics in 1500s  No evidence in pre-colonial New World  1781 pandemic o 2/3 of Rome and ¾ of Britain infected o North America, West Indies and South America 1918 Influenza Pandemic  Spanish flu o Came from end of WWI o Huge censorship in Spain o Publicize more  ~500 million infected (1/3 of global population)  ~50 million global deaths o more death than WWII o from France to US o in 17 days, 1-72thousands infected  ½ of all deaths among those 20-40 yrs of age o they are usually the bread winners and providers o all pregnant women give birth in convents  hospital doesn’t want to risk lives  23-71% mortality rate – infected pregnant women o women who survived, their children did not nd  Occurred in 3 waves, the 2 being the worst Influenza-North America  500,000 deaths in the US (19,000 in New York City)  300,000 cases in Ontario – 8,700 deaths (1,200 deaths in Toronto in just 3 weeks)  500,000 cases and 14,000 deaths in Quebec o Inuit population was completely lost Pathogen-Influenza virus  Influenza A – most virulent, multi species o Can show up in different reservoir o Mutate a lot  Influenza B – humans, only 1 serotype o Mutate slowly, 2-3 times slower than A  Influenza C – least common, mild o Human, dog, pig  Serotypes differ based on: o Hemagglutinin act as a key  15+ different types o Neuraminidase  9+ different types Transmission  From animal o Ducks and geese  Virus can stay for 100 days near shore or lakes after animal poo it out  In digestive o From pig and raccoon  in digestive and respiratory o from chicken  respiratory receptor and human get it the most from chicken o human  only respiratory Antigenic Drift and Shift  Antigenic Drift o small genetic changes over time  get similar strain of influenza in the future o May be unrecognizable to previously exposed immune system  Antigenic Shift o Abrupt, major shift o New H or N protein, or novel combination o No immunity o Make completely different mutation  Influenza A is for both  Influenza B is antigenic drift Host Risk Factors  First nation and aboriginal are most vulnerable o Doesn’t know if its genetic  Some evidence of genetic factors  Respiratory ailments o CPE, lung fibrosis, decreased lung function  High population densities in temperate
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