Virginia Weekly Influenza Activity Report (Week Ending May 4, 2013)
The Virginia Department of Health monitors the level of activity of influenza-like illness (ILI) each week from October through May. Those are the months when influenza ("flu") is most likely to occur in Virginia, and that time period is referred to as the "flu season".
The Virginia Department of Health uses a number of different data sources to determine the level of flu activity that is occurring each week during flu season. The main data sources that are used to make the weekly flu activity level determination are:
Flu Activity Levels:
Flu surveillance is not designed to count every person who has the disease. That would be nearly impossible because not all people with the disease are diagnosed by a physician and even fewer have their illness confirmed by a laboratory test.
Instead, VDH monitors changes in flu activity from week to week in each of the five health planning regions to look for increases compared to a baseline period. Activity is based on illness complaints that lead people to seek care in a hospital emergency department or urgent care center. Flu-like illness is defined as a fever along with a cough and/or a sore throat.
In addition to looking at changes in the number of visits for flu-like illness in each region from week to week, VDH staff also factor in information about outbreaks that have been reported in each region as well as cases of influenza that have been confirmed by specific laboratory methods.
In order for the weekly flu activity level in Virginia to be comparable to those reported by other states, national definitions established by the Centers for Disease Control and Prevention are followed. The national definitions of flu activity levels are:#
Laboratory-confirmed case = case confirmed by culture, antigen detection by DFA, or PCR.
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