FluWatch report: February 12, 2017 – February 18, 2017 (Week 07)

Overall Summary

  • Many influenza indicators such as laboratory detections, outbreaks and hospitalizations have been stable for the past five weeks.
  • Widespread or localized influenza activity was reported in 30 regions across eight provinces.
  • For a third week in a row, the percentage of tests positive for influenza increased (from 23% in week 04 to 25% in week 07).
  • In week 07, 53 laboratory confirmed outbreaks were reported (down from 67 in the previous week); the majority in long-term care facilities and due to influenza A.
  • In week 07, the number of hospitalizations reported by participating provinces and territories decreased. 
  • A(H3N2) continues to be the most common type of influenza affecting Canadians.
  • The majority of laboratory detections, hospitalizations and deaths have been among adults aged 65+ years.
  • For more information on the flu, see our Flu(influenza) web page.

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Organization:

Date published: 2017-02-24

Influenza/Influenza-like Illness Activity (geographic spread)

In week 07, one region in NB reported no influenza or influenza-like illness activity. Sporadic influenza activity was reported in 16 regions across nine provinces and territories. Localized activity was reported in 24 regions across eight provinces. Widespread activity was reported in two provinces (three regions in QC and two regions in BC). For more details on a specific region, click on the map. 

Figure 1 – Map of overall influenza/ILI activity level by province and territory, Canada, Week 07

Figure 1
Figure 1 Legend

Note: Influenza/ILI activity levels, as represented on this map, are assigned and reported by Provincial and Territorial Ministries of Health, based on laboratory confirmations, sentinel ILI rates and reported outbreaks. Please refer to detailed definitions at the end of the report. Maps from previous weeks, including any retrospective updates, are available in the mapping feature found in the Weekly Influenza Reports.

Figure 1 - Text Description

In week 07, one region in NB reported no influenza or influenza-like illness activity. Sporadic influenza activity was reported in 16 regions across nine provinces and territories. Localized activity was reported in 24 regions across eight provinces. Widespread activity was reported in two provinces (three regions in QC and two regions in BC).

Laboratory Confirmed Influenza Detections

In week 07, the percentage of tests positive for influenza increased from to the previous week to 25%. Peak influenza detections occurred in week 02 at 27%. Since week 02, detections have remained relatively stable (ranging from 23% to 25% in weeks 03 to 07). For data on other respiratory virus detections, see the Respiratory Virus Detections in Canada Report on the Public Health Agency of Canada (PHAC) website.

Figure 2 – Number of positive influenza tests and percentage of tests positive, by type, subtype and report week, Canada, 2016-17, Week 07

Figure 2

The shaded area indicates weeks where the positivity rate was at least 5% and a minimum of 15 positive tests were observed, signalling the start and end of seasonal influenza activity.

Figure 2 - Text Description
Figure 2 - Number of positive influenza tests and percentage of tests positive, by type, subtype and report week, Canada, 2016-17
Report Week A(Unsubtyped) A(H3) A(H1)pdm09 Influenza B
35 0 <5 0 0
36 <5 0 <5 9
37 <5 17 0 <5
38 11 28 <5 <5
39 14 41 <5 7
40 0 47 <5 <5
41 10 31 0 <5
42 14 49 <5 6
43 16 76 <5 <5
44 19 110 <5 9
45 31 150 <5 11
46 52 140 <5 7
47 54 200 0 9
48 91 272 <5 7
49 148 414 <5 12
50 305 467 <5 18
51 535 750 <5 17
52 857 1064 <5 33
1 1444 1360 <5 38
2 1516 2118 10 39
3 1354 1412 0 47
4 1336 1220 <5 47
5 1222 1290 7 62
6 1203 1222 9 81
7 1248 1113 11 91
8 0 0 0 0
9 0 0 0 0
10 0 0 0 0
11 0 0 0 0
12 0 0 0 0
13 0 0 0 0
14 0 0 0 0
15 0 0 0 0
16 0 0 0 0
17 0 0 0 0
18 0 0 0 0
19 0 0 0 0
20 0 0 0 0
21 0 0 0 0
22 0 0 0 0
23 0 0 0 0
24 0 0 0 0
25 0 0 0 0
26 0 0 0 0
27 0 0 0 0
28 0 0 0 0
29 0 0 0 0
30 0 0 0 0
31 0 0 0 0
32 0 0 0 0
33 0 0 0 0
34 0 0 0 0

Nationally in week 07, 2,410 positive influenza detections were reported, which is comparable to the 2,472 detections reported the previous week. The provinces of QC, PE, and NL have reported increases in the percent positivity since the national peak in week 02. To date, 25,336 laboratory confirmed influenza detections have been reported, of which 98% have been influenza A. Influenza A(H3N2) is the most common subtype detected, representing over 99% of subtyped influenza A detections (13573/13642). For more detailed weekly and cumulative influenza data, see the text descriptions for Figures 2 and 3 or the Respiratory Virus Detections in Canada Report.

Figure 3 – Cumulative numbers of positive influenza specimens by type/subtype and province/territory, Canada, 2016-17, Week 07

Figure 3
Figure 3 - Text Description
Figure 3 - Cumulative numbers of positive influenza specimens by type/subtype and province/territory, Canada, 2016-17
Reporting
provincesTable Figure 3 - Footnote 1
Weekly (February 12, 2017 to February 18, 2017) Cumulative (August 28, 2016 to February 18, 2016)
Influenza A B Influenza A B A & B
Total
A
Total
A
(H1)pdm09
A
(H3)
ATable Figure 3 - Footnote UnS B
Total
A
Total
A
(H1)pdm09
A
(H3)
ATable Figure 3 - Footnote UnS B
Total
BC 381 2 370 9 27 3744 11 2138 1595 158 3902
AB 123 2 110 11 11 3444 13 3344 87 78 3522
SK 41 0 34 7 0 1397 1 774 623 19 1417
MB 0 0 0 0 0 183 0 78 105 11 194
ON 524 6 437 81 26 7675 38 6219 1418 120 7795
QC 1,063 0 78 985 24 7102 2 512 6588 161 7263
NB 105 0 17 88 1 472 2 69 401 4 476
NS 22 0 0 22 1 210 0 13 197 2 212
PE 26 0 26 0 0 137 2 135 0 1 138
NL 25 0 0 25 0 112 0 43 69 5 117
YT 0 0 0 0 0 197 0 150 47 2 199
NT 6 0 6 0 1 41 0 41 0 1 42
NU 3 0 3 0 0 58 0 57 1 1 59
Canada 2319 10 1081 1228 91 24772 69 13573 11131 563 25336
PercentageTable Figure 3 - Footnote 2 96% 0% 47% 53% 4% 98% 0% 55% 45% 2% 100%

To date, detailed information on age and type/subtype has been received for 17,946 laboratory-confirmed influenza cases (Table 1). Among cases with reported age and type/subtype information, adults aged 65+ accounted for almost half of the reported influenza cases. Among cases of influenza A(H3N2), adults aged 65+ represented  48% of cases, followed by adults aged 20-64 (29% of cases). In the previous influenza A(H3N2)-predominant season in 2014-15, adults aged 65+ represented  58% of cases and adults aged 20-64 represented 27% of cases.

Table 1 - Weekly and cumulative numbers of positive influenza specimens by type, subtype and age-group reported through case-based laboratory reportingTable 1 - Footnote 1, Canada, 2016-17, Week 07
Age groups (years) Weekly (February 12 to February 18, 2017) Cumulative (August 28, 2016 to February 18, 2017)
Influenza A B Influenza A B Influenza A and B
A Total A(H1) pdm09 A(H3) ATable 1 - Footnote UnS Total A Total A(H1) pdm09 A(H3) ATable 1 - Footnote UnS Total # %
<5 >169 <5 37 132 5 >1541 <5 650 891 57 >1598 x%
5-19 >107 <5 10 97 11 >1726 <5 876 850 72 >1798 x%
20-44 162 0 52 110 9 2671 8 1482 1181 70 2741 15%
45-64 199 0 61 138 11 2898 8 1546 1344 77 2975 17%
65+ 727 0 153 574 15 >8705 <5 4122 4583 120 >8825 x%
Total >1364 <5 313 1051 51 17550 25 8676 8849 396 17946 100%
PercentageTable 1 - Footnote 2 96% 0% 23% 77% 4% 98% 0% 49% 50% 2%    

Syndromic/Influenza-like Illness Surveillance

Healthcare Professionals Sentinel Syndromic Surveillance

In week 07, 1.7% of visits to healthcare professionals were due to influenza-like illness, down from 3.1% in the previous week.

Figure 4 - Percentage of visits for ILI reported by sentinels by report week, Canada, 2016-17, Week 07

Number of Sentinels Reporting Week 07: 116

Figure 4

Delays in the reporting of data may cause data to change retrospectively. In BC, AB, and SK, data are compiled by a provincial sentinel surveillance program for reporting to FluWatch. Not all sentinel physicians report every week.

Figure 4 - Text Description
Figure 4 - Percentage of visits for ILI reported by sentinels by report week, Canada, 2016-17
Report week % Visits for ILI
35 0.96%
36 0.96%
37 0.98%
38 0.96%
39 0.94%
40 1.03%
41 2.41%
42 1.04%
43 1.01%
44 1.39%
45 1.32%
46 0.97%
47 1.11%
48 1.07%
49 1.08%
50 1.30%
51 1.73%
52 2.83%
1 1.96%
2 2.22%
3 1.92%
4 2.02%
5 2.31%
6 3.13%
7 1.73%
8  
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19  
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Are you a primary healthcare practitioner (General Practitioner, Nurse Practitioner or Registered Nurse) interested in becoming a FluWatch sentinel?
Please visit our Influenza Sentinel page for more details.

Influenza Outbreak Surveillance

In week 07, 53 laboratory confirmed influenza outbreaks were reported (14 less than the previous week). Among the reported outbreaks: 37 in long-term care (LTC) facilities, eight in hospitals and eight in institutional or community (other) settings. Of the outbreaks with known strains or subtypes, nine were due to influenza A(H3N2), 29 were due to influenza A(UnS) and one was due to influenza B.

To date this season, 791 outbreaks have been reported and the majority (67%) have occurred in LTC facilities. Compared to the same period in the most recent previous A(H3N2) predominant season (2014-15), 1,367 outbreaks were reported, of which 74% occurred in LTC facilities. 

Figure 5 - Overall number of new laboratory-confirmed influenza outbreaksFigure 5 - Footnote 1 by report week, Canada, 2016-17, Week 07
Figure 5
Figure 5 - Text Description
Figure 5 - Overall number of new laboratory-confirmed influenza outbreaks by report week, Canada, 2016-17
Report week Hospitals Long Term Care Facilities Other
35 0 0 0
36 0 0 0
37 0 2 0
38 1 1 1
39 1 3 1
40 0 0 0
41 0 3 0
42 0 3 1
43 0 3 0
44 2 5 2
45 1 1 0
46 2 6 0
47 1 8 0
48 0 2 0
49 1 14 3
50 4 15 4
51 5 32 13
52 7 65 18
1 15 84 22
2 13 83 24
3 19 44 9
4 8 39 8
5 13 36 11
6 4 42 20
7 8 37 8
8 0 0 0
9 0 0 0
10 0 0 0
11 0 0 0
12 0 0 0
13 0 0 0
14 0 0 0
15 0 0 0
16 0 0 0
17 0 0 0
18 0 0 0
19 0 0 0
20 0 0 0
21 0 0 0
22 0 0 0
23 0 0 0
24 0 0 0
25 0 0 0
26 0 0 0
27 0 0 0
28 0 0 0
29 0 0 0
30 0 0 0
31 0 0 0
32 0 0 0
33 0 0 0
34 0 0 0

Provincial/Territorial Influenza Hospitalizations and Deaths

In week 07, 250 influenza-associated hospitalizations were reported by participating provinces and territories, down from  259 reported in the previous week*. Influenza A accounted for nearly all of hospitalizations (97%). The largest proportion of hospitalizations were among adults aged 65+ (64%). A total of less than five intensive care unit (ICU) admissions and 14 deaths were reported in week 07.

To date this season, 3,973 hospitalizations have been reported, of which 98% were due to influenza A. Among cases for which the subtype of influenza A was reported, almost all (2247/2256) were influenza A(H3N2). Adults 65+ accounted for 69% of the hospitalizations. A total of 137 ICU admissions and greater than 160 deaths have been reported. The majority of deaths were reported in adults aged 65+ years. 

Table 2 - Cumulative number of hospitalizations, ICU admissions and deaths by age and influenza type reported by participating provinces and territories, Canada 2016-17, Week 07
Age Groups (years) Cumulative (August 28, 2016 to February 18, 2017)
Hospitalizations ICU Admissions Deaths
Influenza A Total Influenza B Total Total [# (%)] Influenza A and B Total % Influenza A and B Total %
Note: Influenza-associated hospitalizations are not reported to PHAC by: BC, NU, and QC. Only hospitalizations that require intensive medical care are reported by SK. ICU admissions
x Supressed to prevent residual disclosure
0-4 283 9 292 (7%) 7  5% <5  1%
5-19 172 10 182 (5%) 10  7% <5  1%
20-44 209 5 214 (5%) 12  9% 0  0%
45-64 545 7 552 (14%) 43  31% 27 16%
65+ 2700 33 2733 (69%) 65 48% 133  82%
Total 3909 64 3973 (100%) 137 100% >160 100%

Sentinel Hospital Influenza Surveillance

Pediatric Influenza Hospitalizations and Deaths

In week 07, 25 laboratory-confirmed influenza-associated pediatric (≤16 years of age) hospitalizations were reported by the Immunization Monitoring Program Active (IMPACT) network. All  but three cases were due to influenza A. The number of hospitalizations reported in week 07 is below the six year average for the same time period (Figure 7).

To date this season, 373 laboratory-confirmed influenza-associated pediatric hospitalizations were reported by the IMPACT network. Children aged 0-23 months accounted for approximately 39% of hospitalizations. Influenza A accounted for 93% (n=345) of the reported hospitalizations, of which 35% (n=131) were influenza A(H3N2) and the remainder were A(UnS). Additionally, 62 intensive care unit (ICU) admissions have been reported, of which the largest proportion (29%) was reported in children 0-23 months. A total of 43 ICU cases reported at least one underlying condition or comorbidity. No deaths have been reported this season.

In 2014-15, the previous influenza A(H3N2)-predominant season, there were 530 hospitalizations, 65 ICU admissions and less than five deaths reported as of week 07. 

Figure 6 - Cumulative numbers of pediatric hospitalizations (≤16 years of age) with influenza by type and age-group reported by the IMPACT network, Canada, 2016-17, Week 07

Figure 6
Figure 6 - Text Description
Figure 6 - Cumulative numbers of pediatric hospitalizations (≤16 years of age) with influenza by type and age-group reported by the IMPACT network, Canada, 2016-17
Age Group Total
0-5 mo 63
6-23 mo 80
2-4 yr 100
5-9 yr 60
10-16 yr 67

Figure 7 – Number of pediatric hospitalizations (≤16 years of age) with influenza reported by the IMPACT network, by week, Canada, 2016-17, Week 07

Figure 7

The shaded area represents the maximum and minimum number of cases reported by week from seasons 2010-11 to 2015-16.

The number of hospitalizations reported through IMPACT represents a subset of all influenza-associated pediatric and adult hospitalizations in Canada. Delays in the reporting of data may cause data to change retrospectively.

Figure 7 - Text Description
Figure 7 - Number of pediatric (≤16 years of age) hospitalizations reported by IMPACT sentinel hospital network, by week, Canada, 2016-17
Report week 2016-17 Average Min Max
35 0 0 0 0
36 1 0 0 0
37 0 1 0 2
38 0 1 0 2
39 3 0 0 1
40 2 0 0 1
41 0 1 0 2
42 4 1 0 1
43 3 1 0 3
44 6 2 1 4
45 3 3 2 4
46 5 5 1 13
47 3 5 0 9
48 7 10 1 22
49 10 15 2 28
50 20 24 4 47
51 17 35 4 71
52 38 47 7 92
1 48 37 3 75
2 28 36 6 60
3 38 37 2 67
4 43 34 5 47
5 28 39 10 57
6 34 38 15 79
7 25 41 15 118
8 #N/A 48 25 134
9 #N/A 59 12 172
10 #N/A 48 17 114
11 #N/A 45 17 118
12 #N/A 39 14 96
13 #N/A 33 14 57
14 #N/A 27 12 56
15 #N/A 25 14 56
16 #N/A 22 10 41
17 #N/A 18 9 37
18 #N/A 15 6 28
19 #N/A 10 5 18
20 #N/A 9 4 18
21 #N/A 6 2 10
22 #N/A 4 1 7
23 #N/A 2 0 4
24 #N/A 2 0 5
25 #N/A 1 0 3
26 #N/A 1 0 2
27 #N/A 0 0 2
28 #N/A 1 0 1
29 #N/A 0 0 2
30 #N/A 0 0 0
31 #N/A 0 0 0
32 #N/A 0 0 1
33 #N/A 0 0 0
34 #N/A 1 0 2

Adult Influenza Hospitalizations and Deaths

In week 07, 88 laboratory-confirmed influenza-associated adult (≥20 years of age) hospitalizations were reported by the Canadian Immunization Research Network (CIRN). All but one case were due to influenza A and the majority of cases  (77%) occurred in adults aged 65+.

To date this season, 933 laboratory-confirmed influenza-associated adult (≥20 years of age) hospitalizations have been reported by CIRN. All but eight hospitalized cases were due to influenza A. Adults aged 65+ accounted for 77% of hospitalizations. To date, approximately 49 intensive care unit (ICU) admissions have been reported. A total of 31 ICU cases reported at least one underlying condition or comorbidity. The median age of patients admitted to the ICU was 69 years. Approximately 30 deaths have been reported this season, the majority in adults aged 65+. The median age of reported deaths was 84 years. 

Figure 8 - Cumulative numbers of adult hospitalizations (≥20 years of age) with influenza by type and age-group reported by CIRN, Canada, 2016-17, Week 07

Figure 8
Figure 8 - Text Description
Figure 8 - Cumulative numbers of adult hospitalizations (≥20 years of age) with influenza by type and age-group reported by the CIRN network, Canada, 2016-17
Age Group Total
20-44 yr 71
45-64 yr 148
65+ yr 714

Figure 9 – Percentage of hospitalizations, ICU admissions and deaths with influenza by age-group (≥20 years of age) reported by CIRN, Canada 2016-17, Week 07

Figure 9

The number of hospitalizations reported through CIRN represents a subset of all influenza-associated adult hospitalizations in Canada. Delays in the reporting of data may cause data to change retrospectively.

Figure 9 - Text Description
Figure 9 - Percentage of hospitalizations, ICU admissions and deaths with influenza reported by age-group (≥20 year of age), CIRN, Canada, 2016-17
Age-group (years) Hospitalizations (n= >933) ICU admissions (n= <44) Deaths (n= <28)
- Supressed due to small values
20-44 7.6% 6.0% -
45-64 15.9% 23.4% 3.0%
65+ 76.5% 70.2% 96.6%

During the 2016-17 influenza season, the National Microbiology Laboratory (NML) has characterized 814 influenza viruses [742 A(H3N2), 19 A(H1N1), 53 influenza B].  All but one influenza A virus (n=741) and all 53 influenza B viruses characterized were antigentically or genetically similar to the vaccine strains included in both the trivalent and quadrivalent vaccines. Thirty influenza B viruses were similar to the strain included only in the quadrivalent vaccine.

Table 3 – Influenza strain characterizations, Canada, 2016-17, Week 07
Strain Characterization ResultsTable 3 - Footnote 1 Count Description
Influenza A (H3N2)
Antigenically
A/Hong Kong/4801/2014-like
223 Viruses antigenically similar to A/Hong Kong/4801/2014, the A(H3N2) component of the 2016-17 Northern Hemisphere's trivalent and quadrivalent vaccine.
GeneticallyTable 3 - Footnote 2
A/Hong Kong/4801/2014-like
518

Viruses belonging to genetic group 3C.2a. A/Hong Kong/4801/2014-like virus belongs to genetic group 3C.2a and is the influenza A(H3N2) component of the 2016-17 Northern Hemisphere's trivalent and quadrivalent vaccine.

Additionally, genetic characterization of the 223 influenza A (H3N2) viruses that underwent HI testing determined that 188 viruses belonged to genetic group 3C.2a and 32 viruses belonged to genetic group 3C.3a. Sequencing is pending for the remaining 3 isolates. The majority of viruses belonging to genetic group 3C.3a are inhibited by antisera raised against A/Hong Kong/4801/2014Table 3 - Footnote 3.

Antigenically
A/Indiana/10/2011-likeTable 3 - Footnote 4
1

Viruses antigenically similar to A/Indiana/10/2011, a candidate H3N2v vaccine virus.

Influenza A (H1N1)
A/California/7/2009-like 19 Viruses antigenically similar to A/California/7/2009, the A(H1N1) component of the 2016-17 Northern Hemisphere's trivalent and quadrivalent vaccine influenza vaccine.
Influenza B
B/Brisbane/60/2008-like
(Victoria lineage)
23 Viruses antigenically similar to B/Brisbane/60/2008, the influenza B component of the 2016-17 Northern Hemisphere's trivalent and quadrivalent influenza vaccine
B/Phuket/3073/2013-like
(Yamagata lineage)
30 Viruses antigenically similar to B/Phuket/3073/2013, the additional influenza B component of the 2016-17 Northern Hemisphere quadrivalent influenza vaccine.

During the 2016-17 season, the National Microbiology Laboratory (NML) has tested 487 influenza viruses for resistance to oseltamivir and zanamivir and 142 influenza viruses for resistance to amantadine. All viruses were sensitive to oseltamivir and zanamivir. All 142 influenza A viruses were resistant to amantadine (Table 4).

Table 4 - Antiviral resistance by influenza virus type and subtype, Canada, 2016-17, Week 07
Virus type and subtype Oseltamivir Zanamivir Amantadine
# tested # resistant (%) # tested # resistant (%) # tested # resistant (%)
A (H3N2) 429 0 (0%) 429 0 (0%) 131 131 (100%)
A (H3N2v) 1 0 (0%) 1 0 (0%) 1 1 (100%)
A (H1N1) 13 0 (0%) 12 0 (0%) 10 10 (100%)
B 44 0 (0%) 45 0 (0%) N/ATable 4 - Footnote * N/ATable 4 - Footnote *
TOTAL 487 0 (0%) 487 0 (0%) 142 142 (100%)

Abbreviations: Newfoundland/Labrador (NL), Prince Edward Island (PE), New Brunswick (NB), Nova Scotia (NS), Quebec (QC), Ontario (ON), Manitoba (MB), Saskatchewan (SK), Alberta (AB), British Columbia (BC), Yukon (YT), Northwest Territories (NT), Nunavut (NU).

Influenza-like-illness (ILI): Acute onset of respiratory illness with fever and cough and with one or more of the following - sore throat, arthralgia, myalgia, or prostration which is likely due to influenza. In children under 5, gastrointestinal symptoms may also be present. In patients under 5 or 65 and older, fever may not be prominent.

ILI/Influenza outbreaks

Schools:
Greater than 10% absenteeism (or absenteeism that is higher (e.g. >5-10%) than expected level as determined by school or public health authority) which is likely due to ILI.
Note: it is recommended that ILI school outbreaks be laboratory confirmed at the beginning of influenza season as it may be the first indication of community transmission in an area.
Hospitals and residential institutions:
two or more cases of ILI within a seven-day period, including at least one laboratory confirmed case. Institutional outbreaks should be reported within 24 hours of identification. Residential institutions include but not limited to long-term care facilities (LTCF) and prisons.
Workplace:
Greater than 10% absenteeism on any day which is most likely due to ILI.
Other settings:
two or more cases of ILI within a seven-day period, including at least one laboratory confirmed case; i.e. closed communities.

Note that reporting of outbreaks of influenza/ILI from different types of facilities differs between jurisdictions.

Influenza/ILI activity level

1 = No activity: no laboratory-confirmed influenza detections in the reporting week, however, sporadically occurring ILI may be reported

2 = Sporadic: sporadically occurring ILI and lab confirmed influenza detection(s) with no outbreaks detected within the influenza surveillance region Footnote

3 = Localized:

  1. evidence of increased ILIFootnote * and
  2. lab confirmed influenza detection(s) together with
  3. outbreaks in schools, hospitals, residential institutions and/or other types of facilities occurring in less than 50% of the influenza surveillance regionFootnote

4 = Widespread:

  1. evidence of increased ILIFootnote * and
  2. lab confirmed influenza detection(s) together with
  3. outbreaks in schools, hospitals, residential institutions and/or other types of facilities occurring in greater than or equal to 50% of the influenza surveillance regionFootnote

Note: ILI data may be reported through sentinel physicians, emergency room visits or health line telephone calls.


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