Flu Activity and Surveillance

Flu Activity and Surveillance

The Vermont Department of Health monitors flu activity in the state throughout the year using different surveillance methods and creates a report. This weekly report gives a snapshot of emergency room visit, sentinel provider, lab, and outbreak data. The 2021-2022 flu season began the week of October 3, 2021. 
Note: In an ordinary season, MMWR week 20 would be the final report of the season. However, because flu continues to circulate in many areas of the country, extended-season reports will be published at least through MMWR week 25.

Read the latest surveillance report

Influenza surveillance is a collaborative effort among the Centers for Disease Control & Prevention, state health departments, health care providers, laboratories, clinics, and emergency departments. Learn more about influenza surveillance in the United States

Previous Years' End of Season Reports
Title Date Type
Vermont 2020-2021 Influenza End of Season Report
06/11/2021 PDF Download
Vermont 2019-2020 Influenza End of Season Report
05/31/2021 PDF Download
Overview of the 2018-2019 Flu season
06/20/2019 PDF Download
Vermont 2017-2018 Influenza End of Season Report
Overview of the 2017-2018 Flu season
07/06/2018 PDF Download
Vermont 2016-2017 Influenza End of Season Report
Overview of the 2016-2017 Flu season
07/20/2017 PDF Download
Geographic Spread

Please note: The Centers for Disease Control and Prevention (CDC) discontinued data collection for Geographic Spread in the 2021-22 season.

Influenza data is collected and analyzed each week between October and May by the Vermont Department of Health to determine the estimated level of geographic spread of flu in the state. The current geographic spread can be found in the most recent Weekly Surveillance Report. The geographic spread of influenza activity is defined as follows:

No Activity: No laboratory-confirmed cases of influenza and no reported increase in the number of cases of ILI.

Sporadic: Small numbers of laboratory-confirmed influenza cases or a single laboratory-confirmed influenza outbreak has been reported, but there is no increase in cases of ILI.

Local: Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed influenza in a single region of the state.

Regional: Outbreaks of influenza or increases in ILI and recent laboratory confirmed influenza in at least two but less than half the regions of the state with recent laboratory evidence of influenza in those regions.

Widespread: Outbreaks of influenza or increases in ILI cases and recent laboratory-confirmed influenza in at least half the regions of the state with recent laboratory evidence of influenza in the state.

Sentinel ILINet Surveillance

This surveillance data is based upon reports submitted by ILINet - a nationwide group of medical offices that act as influenza sentinels. Sentinel providers report the number of patients with an influenza-like illness (ILI) seen by their practices each week. The aggregated ILI data are analyzed as part of our monitoring of statewide ILI activity.

Ten medical practices located throughout the state currently partner with the Health Department as sentinels, with at least one practice located in each of the state’s five influenza surveillance regions.

Join ILINet — Medical professionals in family practices, internal medicine offices, urgent care centers, emergency rooms, college student health centers, and pediatric practices are invited to join ILINet. Learn more about becoming a sentinel provider or call (802) 863-7240.

Laboratory Testing

The Vermont Department of Health Laboratory (VDHL) tests specimens for influenza to identify which strains are currently causing illness in the state. VDHL only tests specimens from sentinel providers and during outbreaks. If your facility is experiencing a flu outbreak, please call the Health Department at (800) 640-4374 or (802) 863-7240.

See lab testing information

Domestic and International Influenza Surveillance