Influenza Sentinel Surveillance Program

By watching for outbreaks of flu and testing for different strains of flu, public health agencies can help prepare for and control outbreaks, determine appropriate treatments, assess the usefulness of antiviral drugs, and evaluate the effectiveness of vaccines.

Each week, sentinel physicians, university health centers, hospitals/medical centers and public health agencies across the state report "influenza-like illness" (ILI) to the national Centers for Disease Control and Prevention (CDC) and collect representative samples for virus strain identification. The reports include the total number of patient visits to each practice or agency for that week and the number of those patients with symptoms of influenza-like illness (ILI), broken down into five age groups. For purposes of this surveillance program, the ILI case definition is a fever of 100 degrees F or higher along with a cough or sore throat.

For the 2009-2010 flu season, 96 health providers in 55 counties throughout the state have been regularly reporting influenza-like illness to CDC. This group of sentinels includes a wide variety of physician practice types (pediatrics, family practice and internal medicine) in 33 local health department and local health district offices, 38 private practices, 6 hospitals, and 19 college and university student health centers. Nine more sentinel sites were added in Mecklenburg County during the first week in November to improve coverage in that heavily populated area of the state, bringing the total to 104. In addition to tracking seasonal and H1N1 flu cases among North Carolina residents, this system enables North Carolina and CDC to monitor influenza in a very diverse student population that includes students from other states and countries.

These sentinel sites help public health personnel monitor the spread of influenza in the state more effectively than before. Timely identification of circulating influenza virus strains can help detect new strains with pandemic potential and can also help determine whether antiviral drugs might be useful in preventing or treating ILI.

The current influenza sentinel surveillance program began on October 4, 2009.

For North Carolina's flu season reports for 2009-2010 and previous flu seasons, see the N.C. Influenza Update (updated weekly). For comparable national data, see the CDC weekly reports. North Carolina flu and pneumonia mortality data is published in the N.C. Detailed Mortality Statistics annual report (see ICD 10 codes J10-J18) on the State Center for Health Statistics web site.

General information about influenza is available on the N.C. DHHS flu page, flu.nc.gov, and on the CDC’s seasonal flu web page and H1N1 flu web page.

North Carolina's General Communicable Disease Control Branch and the State Laboratory of Public Health have continuously participated in the U.S. Influenza Sentinel Physicians Surveillance Network since the 2000-2001 flu season.