2017 -2018SEASON

INFLUENZA AND RSV SUMMARY

Every influenza season is unique with variation in the number of cases reported, timing of the season, and circulating strains.

Influenza in Arizona 2017–2018

The 2017–2018 influenza season was record-breaking with the most cases reported in a single season in the past decade, eclipsing the 2009 pandemic. During the 2009 pandemic, there were over 20,000 cases identified and in the peak week, there were 2,835 cases reported.

Rates (per 100,000)

< 200

200 to 299

300 to 399

>400

<400

400–599

600–899

≥900

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

Influenza A and Influenza B circulated simultaneously, at different levels, throughout the 2017–2018 season. Overall, influenza A/H3 was the predominant strain (A/H1, B/Victoria & B/Yamagata).

February 2018October 2017 September 2018

12,448 12,594

23,657

13,086

35,610

2013–14 2014–15 2015–16 2016–17 2017–18

6%

74%

4%

16%

During the 2017–2018 season, there were a total of 186 pediatric deaths nationally, the highest number of influenza-associated deaths in children reported since the 2009 pandemic.

Influenza in Arizona 2017–2018

Arizona reported five influenza-associated pediatric deaths in the 2017–2018 season. Two were associated with influenza A, and three with influenza B.

PCR testing conducted at the Arizona State Public Health Laboratory in the 2017–2018 season was used to identify strains of influenza circulating in Arizona.

0

100

200

300

400

500

600

700

800

900

1000

# o

f S

pe

cim

en

s P

osi

tiv

e f

or

Infl

ue

nza

Month of Test Completion

B/Yamagata B/Victoria A (H3) A (H1N1) pdm09

Influenza-like Illness (ILI) Surveillance from Sentinel Outpatient Providers

Information on outpatient visits to health care providers for influenza-like illness is collected through the U.S. Outpatient ILI Surveillance Network (ILINet). Outpatient providers around the nation, including Arizona, are enrolled. ILINet data captures individuals who may have influenza, but may not have had a laboratory test conducted. This data is used in addition to lab reported influenza cases to further illustrate what is occurring during the influenza season.

Influenza in Arizona 2017–2018

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

% o

f V

isit

s fo

r IL

I

Week Ending Date

ILI % ILI% Baseline Threshold (AZ)

Influenza-like illness: Defined as a fever of at least 100ºF plus either a cough or a sore throat. In weeks when a relatively low number of enrolled facilities report data, the ILI proportion may not be as representative of Arizona activity as for other weeks. The state ILI baseline is 1.3% and the epidemic threshold is 2.6%*.

*Note: The baseline is defined as the mean of the state ILI% in weeks in the 2014–2017 Influenza seasons in which two or more consecutive weeks accounted for less than 2% of the season’s total number of specimens testing positive for influenza at the Arizona State Public Health Laboratory. The epidemic threshold is defined as the mean plus two standard deviations.

The 2017–2018 RSV season was record-breaking, with the most cases reported in a single season in the past decade.

RSV in Arizona 2017–2018

Rates (per 100,000)

<50

50-99

100–199

≥200

Infants less than 1 year of age were the most affected; however, in the past several years there has been a notable increase in the older age groups.

700

0

200

400

600

800

October 2017 February 2018 September 2018

2,987

5,436

4,302

5,354

6,726

2013-14 2014-15 2015-16 2016-17 2017-18

2,881

1,649

240

8191,128

<1 Y 1-4 Y 5-14 Y 15-64 Y ≥65 Y

The 2017–2018 RSV season followed a similar trend to the 5 season average, with the peak number of cases being reported in February; however, the 2017–2018 RSV season peak was significantly higher than the 5 season average.