E-final 3e
Terms
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- Influenza agent
- Agent – RNA virus, 3 types (A,B and C) subtypes of H (Hemagglutinin) and N (Neuraminidase) factors emerge in strains of A as a result of re-assortment H1N1, H5N1, H2N3, etc. Sub-types are important Natural protection from cyclic disease Antigen choice for vaccines each year Key animal sources wild and domestic birds (especially aquatic species) Chickens, ducks, geese Pigs (swine)
- Influenza transmission
- Primarily airborne and droplet transmission from person-to-person Can also occur via indirect transmission, since virus can survive in some environments for hours
- Influenza disease
- Incubation period – 1-3 days Symptoms – lasting 3-5 days Sudden onset of fever / chills Headache Myalgias (muscle aches) Cough
- Influenza outcome
- Most recover fully after 1-2 weeks Death often occurs from secondary bacterial or viral pneumonia other underlying systemic disease Average of 36,000 deaths/year in US most frequently in the very young or very old
- Influenza diagnostics
- Symptomatic basis Culture of organism (1-4 days) Rapid tests for viral antigen Serologic tests demonstrating a rise in specific titers Diagnostic tests are not particularly useful in clinical care of patient
- Influenza distribution
- Worldwide, with epidemic cycles of specific strains most often offset 6 months between northern and southern hemispheres In epidemics, 10-20% of the population may experience symptomatic disease, with severe disease (requiring hospitalization) at rates of 50-800/100,000/cycle
- Graphs & maps
- (look at lecture)
- Influenza prevention & treatment
- Vaccination, especially for high-risk populations Prophylactic and therapeutic intervention with one of several pharmacologic agents Adequate personal hygiene regarding unprotected coughs and hand-to-mouth transmission (hand-washing)
- Influenza pandemics
- First pandemic described in the late 16th century (Europe) Pandemics have occurred 3 times in the 20th century
- Influenza pandemics (ex)
- Pandemics have occurred in: 1918 (Spanish ‘flu, H1N1*) 1957 (Asian, H2N2) 1968 (Hong Kong, H3N2) Recent scare: Hong Kong 1997-8 (H5N1) “Avian†flu 2003-present (H5N1) * subtype determined in the last 3-4 years
- 1918 pandemic
- First case identified at Fort Riley army camp in Kansas in the spring of 1918 in one week, 500 cases identified 48 soldiers died transmission then slowed, but did not disappear entirely Flu returned to the US in the fall of 1918 with army personnel reemerged at Fort Devans - a supply depot - near Boston, in mid-September 17,000+ cases at Devans by the end of October, with 800+ deaths (~5% CF) meanwhile the flu also spread to the general population through the fall and into winter Urban populations hard hit large gatherings occurred in support of war effort, facilitating spread rail network enabled spread up and down East Coast and inland some towns set quarantines and blockades to keep infection out; some required use of gauze masks by all people in public settings Global impact 20+ million people worldwide DIED of flu and its complications in 1918-19 600,000 died in the US alone Deaths did not occur primarily in the elderly, as in other outbreaks of flu, but in young adults
- 1918 pandemic context
- WWI underway in Europe 1.5 million US soldiers went to Europe in 1918 by ship (high morbidity/mortality on ships) trench warfare conditions which facilitated transmission troop movements in Europe carried disease to other countries, including Italy, France, Spain and Britain no antibiotics for secondary infections
- CDC pandemic concerns
- New influenza pandemic considered inevitable Little warning - 1 to 6 months between identification and disease arrival in US Simultaneous outbreaks around country Prolonged impact expected - weeks to months at the community level Inadequate and inequitably distributed supplies - vaccine, anti-virals, antibiotics
- Pandemic preparedness
- Maintain/strengthen influenza surveillance worldwide Increase routine coverage of influenza and pneumococcal vaccination efforts Support new vaccine development methods Pre-pandemic planning by all levels of government and other stakeholders