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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.