Unlike other reportable diseases, MDH does not request that every case of influenza or every patient who goes to the doctor with influenza symptoms be reported to MDH. Tracking each case would overburden health care providers as well as MDH, without significant benefit. Instead, MDH uses several different surveillance programs to determine the burden of influenza disease in Minnesota each week (influenza-like illness [ILI] outbreaks at schools and long-term care facilities, outpatient/clinic visits for ILI, laboratory-confirmed influenza in hospitalized patients, and laboratory testing for influenza and other respiratory disease).

Keeping Track of Flu in Minnesota

Many people get sick with flu every year in Minnesota without ever seeing a doctor or reporting their illness. Therefore, MDH uses various indicators to find out how widespread the flu is in Minnesota each week, rather than trying to track every case. The MDH Public Health Laboratory (PHL) also tests selected influenza specimens to monitor which flu strains are circulating each flu season.

Hospitalized Surveillance

Hospitals report to MDH when they have a patient admitted to the hospital with laboratory-confirmed influenza. Hospitals are asked to submit specimens to MDH-PHL for influenza testing. MDH provides guidance on infection control and outbreak management, including the use of antiviral medication for treatment and prevention.

Sentinel Surveillance

Physicians and health care providers across the state help to monitor influenza throughout the flu season. Sentinel providers fill out a weekly report detailing the number of patients they've seen with influenza-like illness. They also submit additional influenza specimens to the MDH Public Health Lab according to the Sentinel Surveillance program guidelines.

Long-Term Care Facility Surveillance

Facilities report to MDH when they have a suspected or laboratory confirmed influenza outbreak. Specimens can be submitted to MDH-PHL for influenza testing. MDH provides guidance on infection control and outbreak management, including the use of antiviral medication for treatment and prevention.

School Surveillance

Minnesota K-12 schools report outbreaks of ILI to MDH when the number of students absent with ILI reaches 5 percent of total enrollment or three or more students with ILI are absent from the same elementary classroom. These reports, although not based on laboratory confirmation, help determine the impact of influenza on school age children in concordance with other surveillance activities.

MLS Laboratory Surveillance

The MN Lab System (MLS) Laboratory Influenza Surveillance Program is made up of more than 100 clinic- and hospital-based laboratories, voluntarily submitting testing data on a weekly basis. These laboratories perform rapid testing for Influenza and Respiratory Syncytial Virus (RSV). Significantly fewer labs, a total of seven, perform confirmatory culture testing for Influenza and RSV. Tracking the laboratory results assists health care providers with patient diagnosis of influenza-like illness and provides an indicator as to the progression of the influenza season as well as prevalence of disease in the community. If your laboratory is interested in participating in this program, please call 651-201-5581.

MLS Virology Laboratory Isolate Surveillance

Viral isolates are subtyped to monitor for the introduction of new influenza virus strains and compared to the current vaccine subtypes. MDH-PHL performs hemagglutinin subtyping on isolates submitted from virology laboratories serving MN patients. Selected influenza isolates are forwarded to CDC for neuraminidase subtyping.