Connecticut Seasonal Influenza Statistics



In Connecticut, the Department of Public Health uses multiple systems to monitor circulating influenza viruses. During the influenza season, weekly flu updates are posted from October of the current year, through May of the following year. Annual summaries are also posted for comparison. The national flu picture may vary from what we are seeing on a state level.


This Week's Flu Update



Current Influenza Season Weekly Updates


To see how this year's influenza season has progressed, please click on the MMWR Week number that corresponds with the week's beginning and end date you are interested in seeing. Each report is progressive and includes data starting from the beginning of this flu season.


All data are preliminary and subject to change.







Influenza Activity
2019 7 February 10, 2019 February 16, 2019 Widespread
2019 6 February 3, 2019 February 9, 2019 Widespread
2019 5 January 27, 2019 February 2, 2019 Widespread
2019 4 January 20, 2019 January 26, 2019 Widespread
2019 3 January 13, 2019  January 19, 2019  Widespread 
2019 2 January 6, 2019 January 12, 2019 Widespread
2019 1 December 30, 2018 January 5, 2019 Widespread
2018 52 December 23, 2018 December 29, 2018 Widespread
2018 51 December 16, 2018 December 22, 2018 Widespread
2018 50 December 9, 2018 December 15, 2018 Regional
2018 49 December 2, 2018 December 8, 2018 Regional
2018 48 November 25, 2018 December 1, 2018 Regional
2018 47 November 18, 2018 November 24, 2018 Regional
2018 46 November 11, 2018 November 17, 2018  Local 
2018 45 November 4, 2018 November 10, 2018 Local
2018 44 October 28, 2018 November 3, 2018 Local
2018 43 October 21, 2018 October 27, 2018 Sporadic
2018 42  October 14, 2018 October 20, 2018 Sporadic
October 7, 2018
October 13, 2018



Connecticut Annual Summaries


National Statistics


Weekly national updates are available from the Centers for Disease Control and Prevention's (CDC) FluView website.


International Statistics


International influenza activity is available at the World Health Organization website.


Connecticut's Influenza Surveillance Systems

  • The EpiCenter System: This system receives near real-time reports on ED visits from all 38 licensed, hospital emergency departments in Connecticut. Data include a description of the chief complaint, or reason for visit, including fever/flu. The EpiCenter system replaced the Hospital Emergency Department Syndromic Surveillance system (HEDSS). During 2017-2018, 18 additional emergency department facilities began sending data to the EpiCenter, and caution should be used when comparing EpiCenter surveillance data to historical HEDSS data.
  • Sentinel Provider Surveillance: Reporting of influenza-like illness (ILI) is conducted through a statewide network of volunteer outpatient providers known as ILINet. The proportion of patients exhibiting ILI is reported to the DPH on a weekly basis. ILI is defined as a cough and/or sore throat in the absence of a known cause, and the presence of a fever >100o F. 
  • Influenza-associated Hospitalizations and/or Deaths: Providers are required to report influenza-associated hospitalizations and influenza-associated deaths, they are not required to report any positive influenza test results. Data collected describe the more serious illnesses associated with influenza infections.
  • Laboratory Surveillance. In Connecticut, positive influenza results are reportable by the laboratory conducting the test. Rapid antigen results are only reportable by laboratories with electronic file reporting. These results are used to determine what types, subtypes, and strains are circulating.
 Influenza Activity Classification Definitions


No Activity No laboratory-confirmed cases AND no increase in the number of cases of ILI.
Sporadic Activity Small numbers of lab-confirmed cases OR lab confirmed outbreak in one institution, but NO increase in cases of ILI.
Local Activity Outbreaks of influenza or increases in ILI cases AND recent laboratory-confirmed influenza in a single region of the state.
Regional Activity Outbreaks of influenza or increases in ILI cases AND recent laboratory-confirmed influenza in at least 2 but less than half of the regions of the state with recent laboratory evidence of influenza in those regions.
Widespread Activity 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.




To contact the Epidemiology and Emerging Infections Program, please call 860-509-7994.