Lecture 20- Pandemic Influenza Wednesday, May 20, 20159:44 AMInfluenza Start by talking about influenza virus in generaloFocus on Spanish Lady\great influenza of 1918-1919Virus isolated in 1930s by Andrews, Wilson and LaidlawMechanisms of disease unraveled soon afteroThree typesA, B, CA causes pandemics in human beingsRNA wrapped in protein coat with proteins on surface as welloSpikes of two major typesHemagglutininEnables virus to attach itself to host cell (in respiratory tract in this case)NeuraminidaseEnables funsion of virus with cells, viral RNA released into cell's cytoplasm, migrate to cell nucleus oBoth spikes have many strains that were isolated in 19th-21st centuryH1N1= swine virus with us today (2009-2011)Viral RNA hijacks cell machinery, makes it a viral factory to reproduce the virusoEventually destroys cell itself, very efficient processNearly instantaneous, cannot measure generations of virusesoInfluenza virus has RNA combine in all sorts of ways, genetic characteristics= mutability\instability Involves things like antigen drift\shift, mutation, hybridizationCreates many strains and variants, subtypes tooPart of success story of influenzaNo crossover immunity from one strain to anotherAcquired immunity is strain specificoMutability also explains an epidemiological features of influenzaPandemics= arrive in wavesEach biologically different, different symptoms and different virulencePandemic in 1918 had four wavesInfluenza=reflective of relationships of human beings and animals (birds\horses\pigs)oInterspecies transfers do occurPossibly the way humans contracted disease in first placeAnimal reservoir= source of new strainsoHypothesis= disease reservoir in Asia (China\Asiatic Russia)Misled public health responses with swine flu pandemicSurveillance active in far east but disease arrived in MexicoTransmission Disease with regards to human beings = unknown origins oEarliest clear evidence is literary, from 15th-16th centuriesRecords fragmentary and unreliableoMust look at last few centuries (18th-21st centuries)
18th centuries had many pandemics1729 to '30,'32 to '33,'61 to '62,1781 to 17821788 to 1789.19th century pandemics 1830 to '31, '33, '50 to '51, Great pandemic of 1889 to 189020th century had many Worst was 1918 to '20 and called the Spanish FluoDisease still with us and recurrent Also, there seemed to be a pattern of one major pandemic every centuryViral\airborne disease, transmitted person to personoMore contagious than SARS (prolonged face to face contact required)Flu communicated rapidlyShort incubation period (24-72 hours)oMakes the disease different epidemiologically from other diseasesAt far end of spectrum, not a classic social diseaseNot sensitive to economic conditions, sanitation and diet like malaria or tuberculosis Frequent were humans breath and are large in numbers
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- Spring '10
- case fatality rate, pandemic influenza