FluSurv-NET Case Definition
For FluSurv-NET, a case is defined as a person who is a resident in a defined FluSurv-NET catchment area and tests positive for influenza by a laboratory test ordered by a health care professional within 14 days prior to or during hospitalization. Laboratory confirmation is defined by a positive result of a viral culture, direct or indirect fluorescent antibody staining, rapid antigen test, or molecular assay.
How FluSurv-NET Calculates Hospitalization Rates
A minimum set of data are collected on all identified cases to produce weekly hospitalization rates:
- race and ethnicity
- surveillance site
- date of hospital admission
- positive influenza test result/date
Hospitalization rates are calculated as the number of residents of a defined area who are hospitalized with a positive influenza laboratory test divided by the total population within the defined area. NCHS bridged-race population estimates are used as denominators.
FluSurv-NET coverage area includes more than 70 counties in 14 states that participate in the Emerging Infections Program (EIP) and the Influenza Hospitalization Surveillance Program (IHSP). Participating states include: California, Colorado, Connecticut, Georgia, Iowa, Maryland, Michigan, Minnesota, New Mexico, New York, Ohio, Oregon, Tennessee and Utah.
FluSurv-NET covers more than 29 million people and includes an estimated 9 percent of the U.S. population. The counties covered are located in all 10 Health and Human Services (HHS) regionsexternal icon. The designated FluSurv-NET surveillance area is generally similar to the U.S. population by demographics; however, the information might not be generalizable to the entire country.