HLTB21H3 Lecture Notes - Antigenic Drift, 1918 Flu Pandemic, Influenza Vaccine

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Published on 13 Apr 2013
School
UTSC
Department
Health Studies
Course
HLTB21H3
Professor
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
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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
Occurred in 3 waves, the 2nd 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
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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 climate
Occupational exposure: farmers, veterinarians and slaughterhouse
workers
Environmental Risk Factors
Drainage of wetlands and lagoons
o Would increase risk
o Birds will go to the only place that is left
Favorable temperature and humidity
o Makes it last longer or shorter with temperature and humidity
High density/unventilated animal pens
o Pigs and chicken
Exposure to: live animal markets, infected poultry, commercial pig
farming
Surveillance and health infrastructure
Characteristics
Respiratory droplet transmission
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Document Summary

Seasonal influenza: rates increase in colder seasons due to more people indoors, u. s. between 1976-2006 flu-associated deaths range from. 3,000 to 49,000 per year: 90% of deaths occur in those aged >65 yrs (risk group) Epidemic/pandemic influenza: surges in influenza cases/deaths caused by a highly virulent and infectious strain. Can show diff peeks: can be differences in risk groups and/or seasonality. Limited lasting immunity for influenza: measles- life long once contracted and need large population density, influenza- no immunity, small population. First evidence in 1400s and 1500s: none in new world due to no domestic animals. 1781 pandemic: 2/3 of rome and of britain infected, north america, west indies and south america. Spanish flu: came from end of wwi, huge censorship in spain, publicize more. ~500 million infected (1/3 of global population) ~50 million global deaths: more death than wwii, from france to us in 17 days, 1-72thousands infected.

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