2017-2018 Influenza Season, Boston - Boston Public Health ... › healthdata ›...
Transcript of 2017-2018 Influenza Season, Boston - Boston Public Health ... › healthdata ›...
2017-2018 Influenza Season, Boston
Communicable Disease Control Division
Infectious Disease Bureau
Boston Public Health Commission
Boston Public Health CommissionCommunicable Disease Control Division
Influenza Surveillance, Boston, 2017-2018
• The 2017-2018 influenza season
refers to the period between
10/1/2017-5/5/2018.
• Influenza cases diagnosed in Boston
and confirmed by any laboratory test
must be reported to the city health
department (Boston Public Health
Commission, [BPHC]).
SLIDE 1
Boston Public Health CommissionCommunicable Disease Control Division
Influenza Surveillance, Boston, 2017-2018
• BPHC syndromic surveillance data are used to
track influenza-like illness (ILI) visits at
Emergency Departments (EDs) in Boston.
• The %ILI represents the percent of all ED visits
attributed to ILI based on chief complaint data.
• During the season, data are used to inform
control measures and provide community and
stakeholder situational awareness.
• Data for this report were analyzed by BPHC at
the conclusion of the influenza season.
SLIDE 2
Boston Public Health CommissionCommunicable Disease Control Division
Reported Influenza Cases* and Percent of Emergency Department
Visits Due to Influenza-Like Illness (ILI)**, Boston, 2017-2018
Boston ED ILI data tracks well with laboratory-confirmed reports of influenza.
0%
1%
2%
3%
4%
5%
6%
0
50
100
150
200
250
300
350
400
450
500
550
600
650
% IL
I
Nu
mb
er
of
Cas
es
Week Ending
Influenza Cases %ILI ED
SLIDE 3
Boston Public Health CommissionCommunicable Disease Control Division
Reported Influenza Cases by Influenza Type,
Boston Residents, 2017-2018
0
50
100
150
200
250
300
350
400
450
500
550
600
650
Nu
mb
er
of
Cases
Week Ending
Influenza A Cases Influenza B Cases
SLIDE 4
The proportion of total cases due to influenza B increases as the season progresses. This does not constitute a second wave
of influenza, but rather is consistent with what typically occurs during most influenza seasons.
Boston Public Health CommissionCommunicable Disease Control Division
Percent of Emergency Department Visits* for Influenza-like Illness (ILI), Boston, 2012-2018**
SLIDE 5
4.81%
5.23%
0%
1%
2%
3%
4%
5%
6%
Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug
% I
LI
/ A
ll V
isit
s
Month
2012-2013 2013-2014 2014-2015 2015-2016 2016-2017 2017-2018
*ED ILI visits: All visits to Boston Eds regardless of residence**Predominating influenza A subtypes by season:
2012-13: H3N2 (circulating virus was well matched to vaccine strain)2013-14: H1N1 (circulating virus was well matched to vaccine strain)2014-15: H3N2 (circulating virus demonstrated antigenic drift from vaccine strain)2015-16: H1N1 (circulating virus was well matched to vaccine strain)2016-17: H3N2 (circulating virus was well matched to vaccine strain)2017-18: H3N2 (circulating virus was well matched to vaccine strain)
While the 2017-2018 influenza season had a high percentage of ED ILI visits over a longer period than most prior seasons, the
2012-2013 season also had a relatively long period of increased ILI activity. During the first wave of the 2009 influenza A(H1N1)
pandemic (not shown here), Boston ED ILI peaked at 7.1%.
Boston Public Health CommissionCommunicable Disease Control Division
Characteristics of Reported Influenza Cases, Boston Residents, 2017-2018
Persons hospitalized with influenza had the highest mortality rate.
Total Cases N=4138
N (%)
Hospitalized 772 (19%)
Died (among total cases) 19 (0.5%)
Died (among hospitalized cases) 14 (1.8%)
N (%)
Influenza A * 3022 (73%)
Influenza B * 1115 (27%)
N (%)
Male 1778 (43%)
Female 2360 (57%) *Excludes one case who tested positive with a rapid diagnostic test that does not differentiate between flu types
SLIDE 6
Boston Public Health CommissionCommunicable Disease Control Division
Reported Influenza Cases, Boston Residents, 2017-2018
187
332
488
396
318
57
199
272
841
529
387
131
900 750 600 450 300 150 0 150 300 450 600 750 900
< 5
5-17
18-44
45-64
64-85
85+
Number of Cases
Age
Gro
up
(yr
s)
Female
Male
SLIDE 7
<5 yrs9%
5-17 yrs15%
18-44 yrs32%
45-64 yrs22%
65-84 yrs17%
85+ yrs5%
Distribution of Cases,
by Age Group and GenderDistribution of Cases, by Age Group
Persons 18 to 44 years of age accounted for the highest proportion of influenza cases.
Boston Public Health CommissionCommunicable Disease Control Division
Reported Influenza Cases by Age in Boston Residents,
Compared to the Overall Boston Population*, 2017-2018
9.3%
14.6%
32.1%
22.4%
17.0%
4.5%
5.2%
11.5%
52.7%
20.4%
8.6%
1.5%
0% 10% 20% 30% 40% 50% 60%
<5
5-17
18-44
45-64
65-84
85+
Percent of Total
Age
Gro
up
(yr
s)
% of Boston Population % of Reported Influenza Cases
Influenza disproportionately impacts extremes of age, specifically children less than 5 years of age, and persons 65 years
of age and older.
SLIDE 8
Boston Public Health CommissionCommunicable Disease Control Division
Reported Influenza Cases by Race/Ethnicity in Boston Residents,
Compared to the Overall Boston Population*, 2017-2018
5.2%
4.1%
7.0%
18.9%
33.0%
31.8%
4.6%
8.9%
17.5%
24.4%
53.9%
0% 10% 20% 30% 40% 50% 60%
Unknown
Other
Asian
Latino
Black
White
Percent of Total
Rac
e/E
thn
icit
y
Boston Population Reported Influenza Cases
Influenza disproportionately impacts Black residents, and to a lesser extent, Latino residents. This is consistent with data
BPHC has reported over the past several influenza seasons.
SLIDE 9
Boston Public Health CommissionCommunicable Disease Control Division
Influenza A vs. Influenza B Cases by Age Group,
Boston Residents, 2017-2018
Age Group (years)
<5 5-17 18-44 45-64 65-84 85+ Total
Influenza A 82% 72% 74% 71% 72% 66% 73%
Influenza B 18% 28% 26% 29% 28% 34% 27%
SLIDE 10
The overall distribution of influenza types by patient age was statistically significant (p=0.0005). Children less than 5 years of
age were more likely to be infected by influenza A compared with other age groups (p=0.0001). Persons greater than or equal to
85 years of age had a higher proportion of influenza B than other age groups (p=0.0249).
Boston Public Health CommissionCommunicable Disease Control Division
Characteristics of Reported Influenza Cases*, by Age Range,
Boston, 2017-2018
SLIDE 11
Persons greater than or equal to 45 years of age had higher hospitalization and mortality rates. No pediatric influenza
associated deaths were reported in Boston residents. The last pediatric influenza associated death in a Boston resident
occurred in 2012.
Age Group (years)
<5 5-17 18-44 45-64 65-84 85+ Overall
# Cases N=386 N=604 N=1329 N=926 N=705 N=188 N=4138
GenderMale (%) 48% 55% 37% 43% 45% 30% 43%
Female (%) 52% 45% 63% 57% 55% 70% 57%
White (%) 25% 16% 34% 33% 38% 55% 32%
Black (%) 34% 37% 29% 39% 33% 20% 33%
Race Latino (%) 16% 25% 20% 19% 17% 11% 19%
Asian (%) 10% 10% 6% 4% 8% 10% 7%
Other** (%) 6% 6% 6% 2% 2% 2% 4%
Hospitalized 8% 4% 7% 21% 42% 70% 19%
Died(N=0)
0% (N=0)
0% (N=0)
0%(N=4) 0.43%
(N=7) 1.00%
(N=8) 4.28%
(N=19) 0.46%
*Reported Cases: Boston Residents only.
**Other is inclusive of American Indian, Alaskan Native, Native Hawaiian, Pacific Islander, and unspecified “other” race.
Boston Public Health CommissionCommunicable Disease Control Division
Characteristics of Reported Influenza Cases* >64 Years of Age,
by Age Range, Boston, 2017-2018
*Reported cases: Boston Residents only.
**Race totals do not total 100% as those with unknown race are not shown
***Other is inclusive of American Indian, Alaskan Native, Native Hawaiian,
Pacific Islander, and unspecified “other” race
Case Demographics
Overall BostonPopulation
Case Demographics
Overall Boston Population
65-84 yrs 65-84 yrs 85+ yrs 85+ yrs
N=705 N/A N=188 N/A
GenderMale 45% 42% 30% 30%
Female 55% 58% 70% 70%
Race**
White 38% 55% 55% 68%
Black 33% 24% 20% 17%
Latino 17% 9% 11% 5%
Asian 8% 9% 10% 7%
Other*** 2% 3% 2% 2%
Hospitalized N/AN=294
42%N/A
N=132 70%
N/A
Died N/A(N=7)
N/A(N=8)
N/A1.00% 4.28%
SLIDE 12
Although racial and ethnic differences are noted in the 65 to 84 year old age group, disparities among Black and Latino residents
persist in persons 85 years of age and greater. Persons 85 years of age and greater were more frequently hospitalized with
increased mortality compared with persons between the ages of 65 and 84 years.
Boston Public Health CommissionCommunicable Disease Control Division
Hospitalization and Mortality Among Laboratory Confirmed Influenza
Cases* Evaluated at Acute Care Hospitals, 2014-2018
Over the past four influenza seasons, the 2017-2018 influenza season had the highest percent of ILI visits. However,
hospitalizations and mortality were highest during the 2014-2015 influenza season, which was also an influenza A(H3N2)
predominant season, though characterized by antigenic drift from vaccine strain.
**2014-15 2015-16 2016-17 2017-18
% Hospitalized 31.6% 20.9% 23.9% 24.8%
% Mortality 5.20% 4.80% 2.40% 1.80%
0%
1%
2%
3%
4%
5%
6%
0%
5%
10%
15%
20%
25%
30%
35%
% M
ort
alit
y
% H
osp
ital
ize
d
*Boston residents only
Predominating influenza A subtypes by season:**2014-15: H3N2 (circulating virus demonstrated antigenic drift from vaccine strain)2015-16: H1N1 (circulating virus was well matched to vaccine strain)2016-17: H3N2 (circulating virus was well matched to vaccine strain)2017-18: H3N2 (circulating virus was well matched to vaccine strain)
SLIDE 13
Boston Public Health CommissionCommunicable Disease Control Division
Confirmed Influenza Cases and ILI Emergency Department (ED)
Visits in Boston Residents, 2017-2018
Confirmed Influenza Cases,
per 100,000 population, 10/1/2017-5/5/2018
ILI ED Visits,
per 100,000 population, 10/1/2017-5/5/2018
Neighborhood
Legend
A/B=Allston/Brighton
BB=Back Bay
CH=Charlestown
DOR=Dorchester
EB=East Boston
FW=Fenway
HP=Hyde Park
JP=Jamaica Plain
MT=Mattapan
RS=Roslindale
RX=Roxbury
SB=South Boston
SE=South End
WR=West Roxbury
SLIDE 14
Boston Public Health CommissionCommunicable Disease Control Division
Comparison of ILI Using Flu Near You (FNY)* and Boston Emergency Department (ED)
Syndromic** Data, 2016-2018
0.0
1.0
2.0
3.0
4.0
5.0
6.0
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
% I
LI
Vis
its (
Bo
sto
n H
osp
itals
)
Metr
o B
osto
n F
NY
% I
LI
Week Ending
Comparison of Flu Near You (FNY) ILI Data and ED Visits for ILI (2016-2018)
Metro Boston FNY % ILI % ILI ED Visits (Boston Hospitals)
↑ start of 2016-2017
influenza season
↑ start of 2017-2018
influenza season
*Flu Near You (FNY) compiles weekly data of ILI activity across the United States. The data come from short, weekly internet-based surveys completed by voluntary participants who indicate whether
they are healthy or have experienced any of a short list of symptoms; the FNY data represented are for the Boston metropolitan area***.**All visits to Boston EDs regardless of residence*** Boston metropolitan area: urbanized area around Boston as defined by the US Census Bureau; approximates towns and cities within the Route 128 belt.
SLIDE 15
Crowd source data (FNY) overall tracks well with ILI. However, the 2017-2018 influenza season’s extreme peak in Boston ED ILI percent
was not well reflected in FNY data. Factors such as aging populations and public perceptions of severity likely impacted reporting to
FNY.
The public may participate by enrolling in FNY at: https://flunearyou.org/
Communicable Disease Control Division
Infectious Disease Bureau
P: (617) 534-5611
F: (617) 534-5905
www.bphc.org/cdc