Colorado Flu Report
2018-2019 Influenza Season
Surveillance for the 2018-2019 influenza season officially began on September 30, 2018, and will run through May 18, 2019. The Colorado Flu Report is published weekly on Tuesdays to provide a concise and up-to-date summary of influenza activity in Colorado. Current surveillance activities include monitoring the following:
Summary for the Week Ending December 8, 2018
Due to delays in reporting numbers are incomplete, especially for the most recent week
As of September 30, 2018, all hospitalized patients with a positive influenza test are considered a confirmed case.
For seasons 2014-15 and 2015-16, the case definition did not include positive rapid influenza tests until influenza was widely circulating. For seasons 2016-17, 2017-18, and 2018-19 the case definition includes all positive influenza tests, including rapid tests, throughout the entire season.
Influenza-Associated Hospitalizations by Age Group
*Due to reporting delays, national cumulative data shown is 1 week delayed from the state-level data.
Table 1 reflects both PCR and rapid antigen testing performed, by current week and cumulative totals for Colorado and the United States. The Colorado weekly and cumulative data includes virologic information on influenza specimens from hospitalized patients tested by hospital laboratories and the Colorado Department of Public Health and Environment laboratory. The national cumulative
data includes virology information reported to the CDC from public health laboratories located in all 50 states, Puerto Rico and the District of Columbia.
Influenza-like Illness (ILI) Surveillance
The percentages shown in Figure 4 are based on the number of primary care office visits assigned a diagnosis consistent with influenza-like illness, divided by the total number of clinic visits for the week. This data comes from Kaiser Permanente and Primary Care Partners. This includes clinics in the North Central, Northeast, Northwest, South and South Central regions of the state.
Percentages shown in Figure 5 are based on the number of emergency department visits of patients with flu influenza like
Baseline levels for outpatient and emergency department visits are calculated using an average of non-influenza weeks for
Positivity Data from Sentinel Laboratories
Influenza positivity data is collected from 23 sentinel clinical laboratories across the state of Colorado. This includes the number of influenza tests performed Sunday through Saturday of each week. Figure 6 shows the number of specimens positive by virus type and the overall percent positivity of influenza testing across all sentinel laboratories.
Pneumonia and Influenza Mortality
Pneumonia and influenza mortality data comes from the National Center for Health Statistics mortality surveillance. This information comes from death certificate data provided by state and vital statistics offices. Data is released two weeks after the week of death. The seasonal baseline is calculated by using data applied from the previous 5 years. The epidemic threshold represents the point at
which the observed proportion of deaths attributed to pneumonia or influenza was significantly higher than what is expected for that time of year in absence of substantial influenza-related mortality. Figure 7 shows P & I mortality for Colorado compared to the national level. Figure 8 shows the trends of P & I data for influenza seasons 2014-15 through 2018-19. More information regarding P & I data can be found: https://gis.cdc.gov/grasp/fluview/mortality.html
Previous Seasons’ Flu Reports
To view the weekly CDC flu surveillance reports, go to: https://www.cdc.gov/flu/weekly/index.htm
COLORADO FLU REPORT | UPDATED 12/11/2018