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Colorado Flu Report


Back to influenza data

Reporting through the week of Dec. 16, 2017.

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

Overview

Surveillance for the 2017-2018 influenza season officially began on Oct. 1, 2017, and will run through May 26, 2018. The Colorado Flu Report is published weekly to provide a concise and up-to-date summary of influenza activity in Colorado. Current surveillance activities include:

  • Reporting of hospitalizations due to influenza.
  • Reporting of influenza-like illness (ILI) visits by selected sites.
  • Reporting of influenza testing activity by sentinel hospital labs.
  • Monitoring circulating influenza viruses through molecular typing, reporting outbreaks of influenza in long-term care facilities (LTCF).
  • Reporting of pediatric deaths due to influenza.

Case reporting

As of Oct. 1, all hospitalized flu cases with any positive flu test will be considered confirmed.  

Synopsis for the Week Ending December 16th:

  • During the week ending Dec. 16, 2017, there were 77 additional hospitalized influenza cases reported. The total number of hospitalizations since the beginning of the 2017-18 season is now 566.
  • Influenza-like illness reported by Kaiser Permanente (which includes providers from the North Central, Northeast, Northwest, South and South Central regions of the state) increased from 1.51% to 1.86%. Influenza-like illness reported by Primary Care Partners (Northwest region) decreased from 1.6% to 1.3%.
  • Sentinel hospital labs (21 of 24 reporting) tested 1,646  specimens and 282 (17%) were positive for influenza.
  • There have been a total of 18 outbreaks associated with influenza for the 2017-18 influenza season.  All outbreaks have been associated with influenza A.
  • No pediatric deaths associated with influenza have been reported for the 2017-18 influenza season.
  • One novel influenza A variant (H1N2v) was detected. An individual hospitalized with influenza in the San Luis Valley was found to be infected with a novel influenza A virus, H1N2v. This individual had exposure to swine at an agricultural event in the week preceding illness onset.

Hospitalizations

Due to reporting delays, the numbers of hospitalizations by week are recalculated each week.

Figure 2. This map displays crude rates of reported influenza-associated hospitalizations, by county. Due to delays in reporting, rates on this map may not include data from the most recent week. 

Table 1. Influenza-Associated Hospitalizations by County, by Report Date, 2017-2018

12/10/17 through 12/16/17

Week 50

10/01/17 through 12/16/17

 Cumulative Reported Cases

County*

2009

H1N1

H3

Type A

Type B

Total

2009 H1N1

H3

Type A

Type B

Total

Rate per

100,000

Total

0

24

51

2

77

5

235

300

26

566

10.2**

Adams

0

3

8

0

11

1

24

35

4

64

12.9

Alamosa

0

1

1

0

2

0

1

1

0

2

12.4

Arapahoe

0

4

4

0

8

0

43

33

1

77

12.1

Boulder

0

3

4

0

7

0

19

21

4

44

13.7

Broomfield

0

1

1

1

3

0

1

4

1

6

9.1

Chaffee

0

0

0

0

0

0

0

1

0

1

5.2

Conejos

0

0

1

0

1

0

1

2

0

3

37.3

Delta

0

0

0

0

0

1

0

1

2

4

13.1

Denver

0

1

10

0

11

0

46

71

5

122

17.6

Douglas

0

2

1

0

3

0

6

10

1

17

5.2

El Paso

0

3

10

1

14

0

25

40

3

68

9.9

Elbert

0

1

0

0

1

0

4

1

0

5

19.9

Fremont

0

0

0

0

0

0

0

0

1

1

2.1

Garfield

0

0

0

0

0

0

5

0

0

5

8.5

Gilpin

0

0

0

0

0

0

0

1

0

1

16.9

Jefferson

0

0

9

0

9

0

16

41

1

58

10.1

Lake

0

0

0

0

0

0

0

1

0

1

13.2

Larimer

0

2

1

0

3

1

21

11

2

35

10.3

Las Animas

0

0

0

0

0

0

1

1

0

2

14.2

Logan

0

0

0

0

0

0

0

2

0

2

9.1

Mesa

0

1

0

0

1

1

5

4

0

10

6.6

Montrose

0

0

0

0

0

0

1

0

0

1

2.4

Morgan

0

0

0

0

0

0

0

3

0

3

10.7

Prowers

0

0

0

0

0

0

0

0

1

1

8.4

Pueblo

0

0

0

0

0

0

5

5

0

10

6.1

Rio Blanco

0

0

0

0

0

0

1

0

0

1

15.4

Rio Grande

0

0

0

0

0

1

0

0

0

1

8.8

Saguache

0

1

0

0

1

0

1

1

0

2

31.2

San Juan

0

0

0

0

0

0

1

0

0

1

143.3

Sedgwick

0

0

0

0

0

0

0

1

0

1

41.3

Weld

0

1

1

0

2

0

8

9

0

17

5.8

 *Counties listed above have reported influenza-associated hospitalizations during the 2017-18 season | ** Rate for state of Colorado

Table 2. Influenza-Associated Hospitalizations by Age Group, Colorado| Oc. 1, 2017 - Dec. 16, 2017

Age

Count

%

CO Population

Rate per 100,000

<6 mo

7

1.2%

33592

20.8

6-23 mo

8

1.4%

101083

7.9

2-4 yr

12

2.1%

199638

6.0

5-18 yr

39

6.9%

1005338

3.9

19-24 yr

11

1.9%

467028

2.4

25-49 yr

63

11.1%

1930853

3.3

50-64 yr

113

20.0%

1056590

10.7

65+ yr

313

55.3%

744159

42.1


Virologic Surveillance

Table 3 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. Of the reported influenza-associated hospitalizations in Colorado, 45% were sub-typed by PCR. The results showed that 235 specimens were H3N2, 5 specimens were H1N1, 1 specimen was H1N2v, and 6 specimens were Yamagata lineage. Similar to the national trend, influenza A has predominated over influenza B in hospitalized patients in Colorado.

Table 3. Virologic Surveillance, Colorado and National Data, 2017-2018

 

 CO Week 50

CO Cumulative Data

National Cumulative Data*

(Dec 10 -Dec 16, 2017)

(Oct 1- Dec 16, 2017)

(Oct. 1, 2017- Dec. 9, 2017)

Total Positive Specimens

77

566

3,711

Influenza A

75 (97%)

540 (95%)

3,228 (87%)

H1N1

0 (0%)

5 (1%)

276 (9%)

H1N2v

0 (0%)

1 (>1%)

4 (>1%)

H3N2

24 (32%)

235 (44%)

2,916 (90%)

Subtyping not performed

51 (68%)

300 (56%)

36 (1%)

Influenza B

      2 (3%)

26 (5%)

483 (13%)

Yamagata lineage

2 (100%)

6 (23%)

318 (66%)

Victoria lineage

0 (0%)

0 (0%)

22 (4%)

Lineage not performed

0 (0%)

20 (77%)

143 (30%)

                          * Due to reporting delays, national cumulative data shown is 1 week delayed from state-level data.

Influenza-Like Illness (ILI) Surveillance

The percentages shown in Figure 3 and 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 from Kaiser Permanente Colorado (which includes providers from the North Central, Northeast, Northwest, South and South Central regions of the state) and Primary Care Partners, P.C. in the Northwest region

Positivity Data from Sentinel Laboratories
Influenza positivity data is collected from 24 sentinel clinical laboratories across the state of Colorado. This includes the number of influenza tests performed Sunday through Saturday of each week. Figure 5 s​hows the number of specimens positive by virus type and the overall percent positivity of influenza testing across all sentinel laboratories.

Rate of Influenza-Associated Hospitalizations by Season
The rates of influenza-associated hospitalizations by season is Figure 6.
​For seasons 2013-14 and 2014-2015,​ the​ case definition did not include positive rapid influenza tests until influenza was widely circulating. ​For seasons 2016-17 and 2017-18, ​the ​case​ ​definition includes all positive influenza tests, including rapid​ tests​​,​ throughout the entire season. So far, the 2017-18 season has had a higher rate of hospitalized cases compared​ with the 2016-17 season.

To view the weekly CDC flu surveillance reports, go to: https://www.cdc.gov/flu/weekly/index.htm 


COLORADO FLU REPORT | UPDATED Dec. 19, 2017