The Ratio of Emergency Department Visits for ILI to Seroprevalence of 2009 Pandemic Influenza A (H1N1) Virus Infection, Florida, 2009.
BACKGROUND
A seroprevalence survey carried out in four counties in the Tampa Bay area of Florida provided an estimate of cumulative incidence of infection due to the 2009 influenza A (H1N1) as of the end of that year's pandemic in the four counties from which seroprevalence data were obtained Methods. Excess emergency department (ED) visits for influenza-like illness (ILI) during the pandemic period (compared to four non-pandemic years) were estimated using the ESSENCE-FL syndromic surveillance system for the four-county area.


RESULTS
There were an estimated 44 infections for every ILI ED visit. Age-specific ratios rose from 19.7 to 1 for children aged <5 years to 143.8 to 1 for persons aged >64 years.


CONCLUSIONS
These ratios provide a way to estimate cumulative incidence. These estimated ratios can be used in real time for planning and forecasting, when carrying out timely seroprevalence surveys is not practical. Syndromic surveillance data allow age and geographic breakdowns, including for children.
Florida Department of Health, Tallahassee, Florida, USA.
Richard S
RS
Hopkins
Florida Department of Health, Tallahassee, Florida, USA.
Aaron
A
Kite-Powell
Florida Department of Health, Tallahassee, Florida, USA.
Kate
K
Goodin
Florida Department of Health, Tallahassee, Florida, USA.
Janet J
JJ
Hamilton
H1N1; Influenza; Pandemic; Surveillance