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L09 Influenza
- respiratory infection transmitted via respiratory secretions with incubation of ~1-5 days
- seasonal December/March survives better in dry environments with little sun
- symptoms: fever, chills, body aches, sore throat, non-productive cough, runny nose,
headache [may lead to respiratory problems/pneumonia
- people who have weak immune system, infants, pregnant women, more subject
- Spanish Flu mainly affected people ages 20-25
- Type A: most virulent, accentuates and mutates
- Type B: only affects humans
- Type C: humans & some animals (dogs/pigs)
- antigenic shift (evolution of subtypes)
- zoonosis: transmission of virus between species (e.g. pigs to humans, or pigs to birds)
- Avian influenza (amongst birds), Pandemic influenza (causes global outbreak), Seasonal
Avian Influenza
- type A affects domestic and wild species
- capable of killing, <50% of those who contract it will die
- occurs when human/bird contact increases but does not transmit human to human
- aquatic birds are natural reservoirs --- can affect chickens/turkeys
- 218 poultry cases from 2003-2006, >124 human deaths (deaths in ferrets, felids, domestic
- high density spreads influenza [poultry centres co-located with humans]
Increased prevalence due to..
- spread via bird saliva, nasal secretion, feces, contact with humans/poultry
- increase in poultry exportations/importations [centres tried to tackle the Avian flu by killing
poultry given subsidies]
- usually death within 10 days lethal but uncommon
- poor sanitary infrastructure
- planetary overload
Pandemic Influenza
- rare but recurrent all over the world (widespread) approximately 3 every century
- another pandemic may be imminent, medical supplies will be inadequate to supply to all
- economic/social disruption every country must be prepared
Æ climate change created anomalies in people
Stages of pandemic
- phase 0 interpandemic phase
- phase 1 novel influenza virus causing outbreaks in at least 1 country, high
- phase 2 outbreaks and epidemics with global spread
- phase 3 end of first pandemic wave
- phase 4 possible second wave
- phase 5 pandemic ends, high immunity
Interpandemic period
- phase 1 no new virus subtypes in humans
- phase 2 circulating animal influenza virus (posing substantial risk)
Pandemic alert!
- phase 3 human infection with new subtype but no/limited human to human spread
- phase 4 small clusters/localized infections
- phase 5 large clusters suggesting better adaptation to humans
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