Seasonal Influenza
Responsible for the influenza that we see every fall and winter. (There are 3 types: A, B, and C)
Influenza A is responsible for most human disease and is the source of all past pandemics
The virus changes slightly during the flu season and as it migrates from the northern to southern hemispheres.
Because the virus changes so frequently, one vaccine does not give lifelong immunity
These changes are monitored and the annual flu vaccine must be designed to try to match these changes.
Named by H#N#s - these signify proteins on the virus envelope – diff. subtypes
Within these subtypes there are different strains
Through prior exposure to similar flu virus strains and from the vaccine, many people have partial immunity to the current circulating strain.
Annually, the US experiences 30 – 40K deaths from seasonal influenza.
Current Avian Flu (H5N1): Human Disease
Human infections have occurred in 10 countries in East Asia & the Pacific, Europe & Eurasia, and the Near East.
There have been a total of 256 confirmed infections and 151 deaths in humans (10/16/06).
Virus is not efficiently spread between birds/humans and humans/humans.
Why Are We Worried About Avian Flu?
Rapid spread through poultry flocks in Asia.
Although rare, has caused severe disease in humans.
Ongoing exposure and infection in humans in rural Asia and Europe (in association with free-ranging poultry flocks).
Co-infection with pig or humans infected with influenza could lead to genetic reassortment.
Could create new flu type easily transmitted from human-to-human (i.e. create a pandemic).
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