FluView: A Weekly Influenza Surveillance Report Prepared by the Influenza Division

2018-2019 Influenza Season Week 20 ending May 18, 2019

All data are preliminary and may change as more reports are received.

An overview of the CDC influenza surveillance system, including methodology and detailed descriptions of each data component, is available at http://www.cdc.gov/flu/weekly/overview.htm.


Influenza activity remained low in United States and was similar to last week. While influenza A(H1N1)pdm09 viruses predominated from October to mid-February, influenza A(H3N2) viruses have been more commonly identified since late February. Small numbers of influenza B viruses also have been reported. Below is a summary of the key influenza indicators for the week ending May 18, 2019:

National and Regional Summary of Select Surveillance Components

HHS Surveillance Regions* Data for current week National data is for the current week
Regional data is for the most recent three weeks

Out-patient ILI Number of jurisdictions reporting regional or widespread activity§ % respiratory specimens positive for flu in clinical laboratories Predominant flu virus reported by public health laboratories
Nation Normal 3 of 54 3.8% Influenza A(H3)
Region 1 Normal 1 of 6 4.8% Approximately equal Influenza A and Influenza B
Region 2 Normal 1 of 4 2.0% Influenza A(H3)
Region 3 Normal 0 of 6 1.2% Approximately equal Influenza A and Influenza B
Region 4 Normal 0 of 8 5.7% Influenza A
Region 5 Normal 0 of 6 4.7% Influenza A(H3)
Region 6 Normal 0 of 5 5.0% Approximately equal Influenza A and Influenza B
Region 7 Normal 0 of 4 2.3% Influenza A
Region 8 Normal 0 of 6 2.8% Influenza A(H3)
Region 9 Normal 1 of 5 5.9% Influenza A(H3)
Region 10 Normal 0 of 4 2.5% Influenza A

† Elevated means the % of visits for ILI is at or above the national or region-specific baseline
§ Includes all 50 states, the District of Columbia, Guam, Puerto Rico, and U.S. Virgin Islands