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Influenza Update—Week 13

April 9, 2019

Data are preliminary.

Pierce County

Influenza activity decreased during week 13 but remains elevated.

Hospitalizations

  • This season, 623 Pierce County residents have been hospitalized with influenza.
  • The median age of hospitalized patients is 64 years (range 9 days to 97 years).
  • The most common premorbid conditions among hospitalized adults are obesity (47%), diabetes (33%) and chronic obstructive pulmonary disease (28%).

Deaths

  • Since Oct. 22, 2018, we identified 35 people who died with influenza.
  • The median age of those who died is 73 years (range 36 to 97 years).
  • Most had at least one premorbid condition that increases the risk of influenza complications.
  • Five had no risk factor for influenza complications other than being older than 65 years.

Viruses

  • Influenza A continues to predominate.
  • 95% of patients hospitalized with influenza tested positive for influenza A and 5% tested positive for influenza B.
  • Of the 175 subtyped viruses, 56% were influenza A H3N2.
  • One patient tested positive for both influenza A H3N2 and influenza A H1N1.

Influenza-like illness

  • The proportion of visits to primary care for influenza-like illness (ILI) remains low.
  • The proportion of visits to emergency department (EDs) and urgent care for ILI decreased during week 13 but remains elevated.

Graph of influenza data. For more information, call (253) 798-6410.

Graph of influenza data. For more information, call (253) 798-6410.

Graph of influenza data. For more information, call (253) 798-6410.

Graph of influenza data. For more information, call (253) 798-6410.

Graph of influenza data. For more information, call (253) 798-6410.

Graph of influenza data. For more information, call (253) 798-6410.

Washington

Influenza activity is elevated and widespread.

Deaths

  • This season, Washington Department of Health received notification of 160 people who died with influenza.

Viruses

  • During week 13, 30.3% of commercial lab specimens tested positive for influenza.
  • Of the 30 influenza A viruses subtyped by public health labs, 24 (80%) were influenza A H3N2.

Influenza-like illness

  • The proportion of outpatient visits for ILI is above baseline.
  • Washington ILI activity is moderate.

Graph of influenza data. For more information, call (253) 798-6410.

Graph of influenza data. For more information, call (253) 798-6410.

United States

Influenza activity decreased during week 13 but remains elevated.

Deaths

  • This season, CDC received notification of 82 children who died with influenza.
  • The proportion of deaths caused by pneumonia or influenza is at the epidemic threshold.

Viruses

  • During week 13, 74% of viruses subtyped by public health labs were influenza A H3N2.
  • Influenza A H3N2 predominates in all 10 Health and Human Services (HHS) Regions.
  • The proportion of influenza B viruses detected remains low.

Influenza-like illness

  • The proportion of outpatient visits for ILI is at or above HHS Regional baselines throughout the country.

Graph of influenza data. For more information, call (253) 798-6410.

Graph of influenza data. For more information, call (253) 798-6410.

Graph of influenza data. For more information, call (253) 798-6410.

Influenza hospitalizations per 100,000 population, 2018-2019 influenza season, weeks 40 through 13

Age

Pierce County

United States

0 to 4 years

51.7

66.1

5 to 17 years

13.5

18.8

18 to 49 years

33.6

23.3

50 to 64 years

88.6

71.9

65 years and older

249.1

181.8

Total

72.5

56.4

Graph of influenza data. For more information, call (253) 798-6410. 

Comments

Influenza seasons typically end with increased detection of influenza B viruses. Last season ended with an increase in influenza B activity coinciding with a second wave of hospitalizations. This season, influenza B activity has stayed low.

Influenza A H1N1 predominated October through December 2018. Then influenza A H3N2 emerged and predominated throughout the United States. More influenza hospitalizations and deaths typically occur when influenza A H3N2 predominates. Older adults are more severely affected by influenza A H3N2 than influenza A H1N1.

In Pierce County, residents hospitalized with influenza A H3N2 are significantly older than those hospitalized with influenza A H1N1 (53.5 vs. 44.7, p=0.03). Seventy-five percent of residents hospitalized with influenza A H1N1 are age 0 to 64 years. Forty-five percent of residents hospitalized with influenza A H3N2 are age 65 years or older. During the 2009 influenza A H1N1 pandemic, influenza mortality was highest among adults age 18 to 65 years.

Influenza A subtypes in Pierce County residents hospitalized with influenza

Age

H1N1

Percent H1N1

H3N2

Percent H3N2

0 to 4 years

12

16%

5

5%

5 to 17 years

5

6%

12

12%

18 to 49 years

18

23%

17

17%

50 to 64 years

23

30%

20

20%

65 years and older

19

25%

44

45%

 

Influenza continues to circulate in Pierce County. CDC’s Advisory Committee on Immunization Practices recommends everyone age 6 months and older be immunized against seasonal influenza as long as influenza circulates.

References

Centers for Disease Control and Prevention. (2019). Weekly United States influenza surveillance report. 2018-2019 influenza season week 13 ending March 30, 2019. Retrieved April 5, 2019 from www.cdc.gov/flu/weekly.

Fowlkes, A. L., Arguin, P., Biggerstaff, M. S., Gindler, J., Blau, D., Jain, S., et al. (2011). Epidemiology of 2009 pandemic influenza A (H1N1) deaths in the United States, April-July 2009. Clinical Infectious Diseases, 52(Supple. 1). doi:10.1093/cid/ciq022.

Grohskopf, L. A., Sokolow, L. Z., Broder, K. R., Walter, E. B., Fry, A. M., & Jernigan, D. B. (2018). Prevention and control of seasonal influenza with vaccines: recommendations of the Advisory Committee on Immunization Practices—United States, 2018-19 influenza season. Morbidity and Mortality Weekly Report, 67(3). Retrieved Aug. 24, 2018 from www.cdc.gov/mmwr/volumes/67/rr/rr6703a1.htm.

Washington State Department of Health. (2019). Washington influenza update. Week 13: March 24, 2019 - March 30, 2019. Retrieved April 5, 2019 from www.doh.wa.gov/DataandStatisticalReports/DiseasesandChronicConditions/CommunicableDiseaseSurveillanceData/InfluenzaSurveillanceData.

 

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