2007-2008: There were 119
hospitalizations and 4 deaths associated
with adult influenza in the Portland
tri-county area (Multnomah, Clackamas,
Washington)
There are two main types of influenza
(flu) virus: Types A and B. Influenza A and B viruses are
responsible for seasonal flu epidemics each year. Influenza A
viruses can be broken down into sub-types. Over the course of a
flu season, different types (A & B) and subtypes of
influenza A viruses can circulate and cause illness. In
addition, influenza viruses are constantly changing through a
process called "antigenic drift." thus the reason for
developing a flu vaccine for a specific season, and the reason
sometimes the vaccine developed doesn't treat the strain
present.
