FluWatch report: May 10 to May 16, 2015 (Week 19)

Overall summary

  • Influenza B continues to be the most common influenza virus circulating in Canada; however, influenza B is past its peak and remains within expected levels for this time of year.
  • Overall, influenza activity in Canada continues to decrease; however, elevated activity was still reported in week 19 (mostly in parts of Central Canada and Newfoundland).
  • Based on laboratory detections, influenza B is having a greater impact on adults less than 65 years of age compared to influenza A(H3N2), which predominated earlier in the season.
  • As of week 19, 7,549 hospitalizations and 576 deaths have been reported from participating regions, which is more than were reported last year at this time (4,862 hospitalizations and 291 deaths).

Are you a primary health care practitioner (General Practitioner, Nurse Practitioner or Registered Nurse) interested in becoming a FluWatch sentinel for the 2014-15 influenza season? Contact us at FluWatch@phac-aspc.gc.ca

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Organization: Public Health Agency of Canada

Date published: 2015-05-22

Influenza/ILI Activity (geographic spread)

In week 19, one region in QC and one region in NL reported widespread activity. Eight regions reported localized activity: MB, ON(5), QC, and NL. Twenty-three regions reported sporadic activity: BC(4), AB(5), SK(3), MB(2), ON(2), QC(4), NL, NB, and NS.

Figure 1. Map of overall influenza/ILI activity level by province and territory, Canada, Week 19

Figure 1

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 on the Flu Activity website.

   Figure 1 Map of overall influenza/ILI activity level by province and territory, Canada, Week 16 - Text Description

In week 19, one region in QC and one region in NL reported widespread activity. Eight regions reported localized activity: MB, ON(5), QC, and NL. Twenty-three regions reported sporadic activity: BC(4), AB(5), SK(3), MB(2), ON(2), QC(4), NL, NB, and NS.

Influenza and Other Respiratory Virus Detections

The number of positive influenza tests decreased from 314 in week 18 to 220 in week 19. Influenza B remained the predominant virus in week 19, representing 93% of influenza detections. Most jurisdictions reported stable or declining levels of influenza detections over recent weeks. To date, 81% of influenza detections have been influenza A, and 99.2% of those subtyped have been A(H3N2) (Table 1). To date this season, detailed information on age and type/subtype has been received for 36,997 cases (Table 2). Adults ≥65 years of age have predominantly been affected by influenza A, accounting for 62% of influenza A detections. Influenza B, while much smaller in numbers, is mainly affecting individuals less than 65 years of age. Adults under the age of 64 years accounted for 59% of influenza B detections.

Figure 2. Number of positive influenza tests and percentage of tests positive, by type, subtype and report week, Canada, 2014-15

Figure 2
   Figure 2 Number of positive influenza tests and percentage of tests positive, by type, subtype and report week, Canada, 2014-15 - Text Description

The number of positive influenza tests decreased from 314 in week 18 to 220 in week 19.

In week 19, detections for all other respiratory viruses decreased from the previous week and are approaching inter-seasonal levels (figure 3).

For more details, see the weekly Respiratory Virus Detections in Canada Report.

Figure 3. Number of positive laboratory tests for other respiratory viruses by report week, Canada, 2014-15

Figure 3 RSV: Respiratory syncytial virus; hMPV: Human metapneumovirus
   Figure 3 Number of positive laboratory tests for other respiratory viruses by report week, Canada, 2014-15 - Text Description

In week 19, detections for all other respiratory viruses decreased from the previous week.

Table 1: Weekly and cumulative numbers of positive influenza specimens by type, subtype and province, Canada, 2014-15
Reporting provincesFootnote 1 Weekly (May 10 to May 16, 2015) Cumulative (August 24, 2014 to May 16, 2015)
Influenza A B Influenza A B
A Total A(H1)pdm09 A(H3) A Footnote (Uns) B Total A Total A(H1)pdm09 A(H3) A(UnS) B Total
BC 3 0 0 3 33 3525 28 2629 868 466
AB 1 0 0 1 25 3701 14 3531 156 937
SK 0 0 0 0 11 1315 0 839 476 311
MB 0 0 0 0 17 1124 1 390 733 214
ON 3 0 3 0 49 11162 50 4714 6398 1456
QC 4 0 0 4 50 11449 4 422 11023 3870
NB 0 0 0 0 6 1195 0 193 1002 530
NS 0 0 0 0 1 511 1 123 387 261
PE 0 0 0 0 0 131 1 128 2 108
NL 5 0 0 5 12 629 0 123 506 70
Canada 16 0 3 13 204 34742 99 13092 21551 8223
Percentage Footnote 2 7.3% 0.0% 18.8% 81.3% 92.7% 80.9% 0.3% 37.7% 62.0% 19.1%
Table 2. Weekly and cumulative numbers of positive influenza specimens by type, subtype and age-group reported through case-based laboratory reportingFootnote 1,Footnote 3, Canada, 2014-15
Age groups (years) Weekly May 10 to May 16, 2015 Cumulative (August 24, 2014 to May 16, 2015)
Influenza A B Influenza A B Influenza A and B
A Total A(H1) pdm09 A(H3) A Footnote (Uns) Total A Total A(H1) pdm09 A(H3) A (UnS) Total # %
<5 0 0 0 0 7 2091 22 809 1260 524 2615 7.1%
5-19 0 0 0 0 14 1781 6 956 819 755 2536 6.9%
20-44 1 0 1 0 32 3443 16 1672 1755 1065 4508 12.2%
45-64 4 0 0 4 36 3874 22 1659 2193 1762 5636 15.2%
65+ 2 0 1 1 44 18745 15 7289 11441 2830 21575 58.3%
Unknown 0 0 0 0 0 120 0 101 19 7 127 0.3%
Total 7 0 2 5 133 30054 81 12486 17487 6943 36997 100.0%
PercentageFootnote 2, 5.0% 0.0% 28.6% 71.4% 95.0% 81.2% 0.3% 41.5% 58.2% 18.8%    

Antiviral Resistance

During the 2014-2015 influenza season, the NML has tested 1,499 influenza viruses for resistance to oseltamivir and 1,444 influenza viruses for resistance to zanamivir. All viruses were sensitive to zanamivir and one influenza A(H3N2) virus was resistant to oseltamivir. A total of 1,390 influenza A viruses (99.9%) were resistant to amantadine (Table 3).

Table 3. Antiviral resistance by influenza virus type and subtype, Canada, 2014-15
Virus type and subtype Oseltamivir Zanamivir Amantadine
# tested # resistant (%) # tested # resistant (%) # tested # resistant (%)
A (H3N2) 901 1 888 0 1372 1371 (99.9%)
A (H1N1) 17 0 15 0 19 19 (100%)
B 581 1 541 0 NATable 3 - Footnote * NA Table 3 - Footnote *
TOTAL 1499 1 1499 0 1391 1390

Influenza Strain Characterizations

During the 2014-2015 influenza season, the National Microbiology Laboratory (NML) has characterized 898 influenza viruses [195 A(H3N2), 18 A(H1N1) and 685 influenza B].

Influenza A (H3N2): When tested by hemagglutination inhibition (HI) assay (n=195), one virus was antigenically similar to A/Texas/50/2012, five showed reduced titers to A/Texas/50/2012 and 189 were antigenically similar to A/Switzerland/9715293/2013, which is the influenza A(H3N2) component recommended for the 2015 Southern Hemisphere influenza vaccine. Additionally, 1,143 A(H3N2) viruses were unable to be tested by HI assay; however, sequence analysis showed that 1,141 belonged to a genetic group that typically shows reduced titers to A/Texas/50/2012.
Influenza A(H1N1):
Eighteen A(H1N1) viruses characterized were antigenically similar to A/California/7/2009.
Influenza B: Of the 685 influenza B viruses characterized, 643 viruses were antigenically similar to B/Massachusetts/2/2012, three viruses showed reduced titers against B/Massachusetts/2/2012, and 39 were B/Brisbane/60/2008-like (Figure 4).

Figure 4. Influenza strain characterizations, Canada, 2014-2015, N = 898

Figure 4

The NML receives a proportion of the number of influenza positive specimens from provincial laboratories for strain characterization and antiviral resistance testing. Characterization data reflect the results of haemagglutination inhibition (HAI) testing compared to the reference influenza strains recommended by WHO.

   Figure 4 Influenza strain characterizations, Canada, 2014-2015, N = 898 - Text Description
Strain Number of specimens Percentage
A/Texas/50/2012-like 1 0%
reduced titres to A/Texas/50/2012 5 1%
A/California/07/2009-like 18 2%
A/Switzerland/97 15293/2013-like 189 21%
B/Massachusetts/2/2012-like 643 72%
reduced titres to B/Massachusetts/2/2012 3 0%
B/Brisbane/60/2008-like 39 4%

Influenza-like Illness (ILI) Consultation Rate

In week 19, the national influenza-like-illness (ILI) consultation rate increased from the previous week to 23.8 consultations per 1,000 (Figure 5).

Figure 5. Influenza-like-illness (ILI) consultation rates by report week, compared to the 1996-97 through to 2012-13 seasons (with pandemic data suppressed), Canada, 2014-2015

Figure 5

No data available for mean rate for weeks 19 to 39 for the 1996-1997 through 2002-2003 seasons. Delays in the reporting of data may cause data to change retrospectively. The calculation of the average ILI consultation rate over 17 seasons was aligned with influenza activity in each season. In BC, AB, and SK, data is compiled by a provincial sentinel surveillance program for reporting to FluWatch. Not all sentinel physicians report every week.

   Figure 5 Influenza-like-illness (ILI) consultation rates by report week, compared to the 1996-97 through to 2012-13 seasons (with pandemic data suppressed), Canada, 2015-16 - Text Description

In week 19, the national influenza-like-illness (ILI) consultation rate increased from the previous week to 23.8 consultations per 1,000.

Influenza Outbreak Surveillance

In week 19, 10 new outbreaks of influenza were reported. Eight outbreaks were reported in long-term care facilities (LTCF) and two in institutional or community settings (Figure 6). Among the outbreaks in which the influenza type was known (n=3), all were associated with influenza B. To date this season, 1,273 outbreaks in LTCFs have been reported and the majority of those with known subtypes were attributable to A(H3N2). There have been a higher number of reported influenza outbreaks to date this season compared to the same period in previous seasons.

Figure 6: Overall number of new laboratory-confirmed influenza outbreaks by report week, Canada, 2014-2015

Figure 6

1 All provinces and territories except NU report outbreaks in long-term care facilities. All provinces and territories with the exception of NU and QC report outbreaks in hospitals. Outbreaks of influenza or influenza-like-illness in other facilities are reported to FluWatch but reporting varies between jurisdictions. Outbreak definitions are included at the end of the report.

   Figure 6 Overall number of new laboratory-confirmed influenza outbreaks by report week, Canada, 2015-2016 - Text Description
Report week Hospitals Long Term Care Facilities Other
35 0 0 0
36 0 0 0
37 0 0 0
38 0 1 0
39 0 5 1
40 0 0 0
41 0 2 0
42 0 3 0
43 0 2 0
44 0 1 0
45 0 2 0
46 0 3 0
47 0 16 1
48 3 17 1
49 2 32 3
50 2 57 13
51 9 94 22
52 8 114 21
53 9 122 35
1 12 152 31
2 8 118 19
3 6 54 12
4 13 64 16
5 7 51 13
6 4 60 10
7 2 45 9
8 0 24 7
9 6 22 10
10 0 32 19
11 5 49 11
12 0 31 4
13 1 19 9
14 1 20 9
15 0 19 2
16 0 15 2
17 0 8 0
18 0 11 3
19 0 8 2

Pharmacy surveillance

Pharmacy surveillance for sales of influenza antivirals has ended for the 2014-2015 influenza season (Figure 7).

Figure 7. Proportion of prescription sales for influenza antivirals by age-group and week, Canada, 2014-15

Figure 7

Note: Pharmacy sales data are provided to the Public Health Agency of Canada by Rx Canada Inc. and sourced from major retail drug chains representing over 2,500 stores nationwide (excluding Nunavut) in 85% of Health Regions. Data provided include the number of new antiviral prescriptions (for Tamiflu and Relenza) and the total number of new prescriptions dispensed by Province/Territory and age group. Age-groups: Infant: 0-2y, Child: 2-18y; Adult: 19-64y; Senior: ≥65y

   Figure 7 Proportion of prescription sales for influenza antivirals by age-group and week, Canada, 2015-16 - Text Description

Pharmacy surveillance has ended for the 2014-15 season.

Sentinel Hospital Influenza Surveillance

Paediatric Influenza Hospitalizations and Deaths (IMPACT)

In week 19, three laboratory-confirmed influenza-associated paediatric (≤16 years of age) hospitalizations were reported by the Immunization Monitoring Program Active (IMPACT) network. All cases were influenza B (Figure 8a). A greater proportion of cases have been reported with influenza B in recent weeks, following the trend in laboratory detections. Among the reported cases, two (67%) were <2 years of age and one (33%) was 10 to 16 years of age. No ICU admissions were reported.

To date this season, 685 hospitalizations have been reported by the IMPACT network, 509 (74%) of which were cases of influenza A. Among cases for which the influenza A subtype was reported, 98% (161/164) were A(H3N2) (Table 4). To date, 85 cases were admitted to the ICU, of which 48 (57%) were 2 to 9 years of age (Figure 9a). A total of 56 ICU cases reported to have at least one underlying condition or comorbidity. Four deaths have been reported.

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

Adult Influenza Hospitalizations and Deaths (CIRN)

Surveillance has ended for the 2014-2015 influenza season.

This season, 2,228 cases have been reported; 1,912 (86%) with influenza A. The majority of cases (81%) were among adults ≥65 years of age (Table 5). One hundred and seventy two ICU admissions have been reported and 128 cases were adults ≥65 years of age. Among the 172 ICU admissions, 27 were due to influenza B (12 in adults 45 to 64 years of age and 15 in adults over the age of 65). A total of 123 ICU cases (72%) reported to have at least one underlying condition or comorbidity. Of the 123 ICU cases with known immunization status, 40 (33%) reported not having been vaccinated this season. One hundred and thirty-five deaths have been reported, 124 (92%) of the deaths were adults >65 years of age (Figure 9b).

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

Table 4 - Cumulative numbers of paediatric hospitalizations with influenza reported by the IMPACT network, Canada, 2014-15
Age groups Cumulative (Aug. 24, 2014 to May 16, 2015)
Influenza A B Influenza A and B
A Total A(H1) pdm09 A(H3) AFootnote (Uns) Total # (%)
0-5m 81 0 18 63 14 95 (13.9%)
6-23m 114 2 36 76 36 150 (21.9%)
2-4y 124 1 38 85 47 171 (25.0%)
5-9y 129 0 44 85 50 179 (26.1%)
10-16y 61 0 25 36 29 90 (13.1%)
Total 509 3 161 345 176 685
% Footnote 1 74.3% 0.6% 31.6% 67.8% 25.7% 100.0%
Table 5 - Cumulative numbers of adult hospitalizations with influenza reported by the PCIRN-SOS network, Canada, 2014-15
Age groups Cumulative (November 15, 2014 to May 2, 2015)
Influenza A B Influenza A and B
A Total A(H1) pdm09 A(H3) AFootnote (Uns) Total # (%)
16-20 3 0 1 2 1 4 (%)
20-44 106 1 56 49 16 122 (5%)
45-64 217 3 99 115 76 293 (13%)
65+ 1586 4 760 822 223 1809 (81%)
Total 1912 8 916 988 316 2228
% Footnote 1 86% 0% 48% 52% 14% 100%

Figure 8 - Number of cases of influenza reported by sentinel hospital networks, by week, Canada, 2014-15

8A) Paediatric hospitalizations (≤16 years of age, IMPACT)

Figure 8A
   Figure 8A Number of cases of influenza reported by sentinel hospital networks, by week, Canada, 2015-16 - Text Description
Report week Influenza A Influenza B
35 0 0
36 0 0
37 2 0
38 1 0
39 1 0
40 1 0
41 2 0
42 1 0
43 3 1
44 4 0
45 4 0
46 9 3
47 8 1
48 15 4
49 30 2
50 41 2
51 56 1
52 65 2
53 47 2
1 53 5
2 43 2
3 33 1
4 25 0
5 12 3
6 9 9
7 14 11
8 5 6
9 5 12
10 6 13
11 7 11
12 0 22
13 1 11
14 2 13
15 2 12
16 2 8
17 0 9
18 0 7
19 0 3

Figure 8B - Number of cases of influenza reported by sentinel hospital networks, by week, Canada, 2014-15

8B) Adult hospitalizations (≥16 year of age, PCIRN-SOS)

Figure 8B Note: Data for week 46 is based on data collected for 1 day only and do not represent the number of hospitalizations for the entire week.
   Figure 8B Number of cases of influenza reported by sentinel hospital networks, by week, Canada, 2015-16 - Text Description
Report week Influenza A Influenza B Untyped
35 n/a n/a n/a
36 n/a n/a n/a
37 n/a n/a n/a
38 n/a n/a n/a
39 n/a n/a n/a
40 n/a n/a n/a
41 n/a n/a n/a
42 n/a n/a n/a
43 n/a n/a n/a
44 n/a n/a n/a
45 n/a n/a n/a
46 3 0 0
47 10 0 0
48 34 0 0
49 43 0 0
50 99 4 0
51 139 0 1
52 239 3 0
53 236 3 0
1 228 2 0
2 159 0 0
3 145 4 1
4 99 9 0
5 118 5 0
6 79 13 0
7 67 18 1
8 68 20 2
9 51 27 0
10 30 38 1
11 14 31 1
12 20 31 0
13 11 27 0
14 10 33 0
15 8 23 0
16 2 20 0
17 0 5 0
18      
19      

Figure 9 - Percentage of hospitalizations, ICU admissions and deaths with influenza reported by age-group, Canada, 2014-15

9A) Paediatric hospitalizations (≤16 years of age, IMPACT)

Figure 9a
   Figure 9A Percentage of hospitalizations, ICU admissions and deaths with influenza reported by age-group, Canada, 2014-15 A) Paediatric hospitalizations (≤16 years of age, IMPACT) - Text Description
Age-group (years) Hospitalizations(n=685) ICU admissions(n=85)
0-5m 13.9% 3.5%
6-23m 21.9% 22.4%
2-4y 25.0% 30.6%
5-9y 26.1% 25.9%
10-16y 13.1% 17.6%

9B) Adult hospitalizations (≥16 year of age, PCIRN-SOS)

Figure 9b
   Figure 9B Percentage of hospitalizations, ICU admissions and deaths with influenza reported by age-group, Canada, 2014-15 B) Adult hospitalizations (≥16 year of age, CIRN) - Text Description
Age-group (years) Hospitalizations (n=2228) ICU admissions(n=172) Deaths (n=135)
16-20 0.2% 0.0% 0.0%
20-44 5.5% 5.2% 2.2%
45-64 13.2% 20.3% 5.9%
65+ 81.2% 74.4% 91.9%

Provincial/Territorial Influenza Hospitalizations and Deaths

In week 19, 37 laboratory-confirmed influenza-associated hospitalizations were reported from participating provinces and territoriesootnote *, which is lower than the number reported the previous week. Of the 37 hospitalizations, 20 (54%) were due to influenza A and 15 (41%) were in patients ≥65 years of age.

Since the start of the 2014-15 season, 7,549 hospitalizations have been reported; 6,540 (87%) with influenza A. Among cases for which the subtype of influenza A was reported, 99.2% were A(H3N2). The majority of cases (70%) were ≥65 years of age (Table 6). A total of 389 ICU admissions have been reported to date: 53% (n=203) were in adults ≥65 years of age and 76% were due to influenza A. A total of 576 deaths have been reported since the start of the season: three children <5 years of age, four children 5-19 years, 43 adults 20-64 years, and 526 adults ≥65 years of age. Influenza A has been reported in 91% of deaths. Adults 65 years of age or older represent 91% of all deaths reported this season. Detailed clinical information (e.g. underlying medical conditions) is not known for these cases.

Table 6. Cumulative number of hospitalizations with influenza reported by the participating provinces and territories, Canada, 2014-15
Age groups Cumulative (24 August 2014 to 16 May, 2015)
Influenza A B Influenza A and B
A Total A(H1) pdm09 A(H3) AFootnote (Uns) Total # (%)
0-4 years 425 5 150 270 83 508 (7%)
5-19 years 258 0 120 138 90 348 (5%)
20-44 years 321 4 168 149 77 398 (5%)
45-64 years 718 12 352 354 197 915 (12%)
65+ years 4762 4 2274 2484 541 5303 (70%)
Unknown 56 1 52 3 21 77 (1%)
Total 6540 26 3116 3398 1009 7549
Percentage Footnote 1 86.6% 0.4% 47.6% 52.0% 13.4% 100.0%

See additional data on Reported Influenza Hospitalizations and Deaths in Canada: 2009-10 to 2014-15 on the Public Health Agency of Canada website.

Emerging Respiratory Pathogens

Human Avian Influenza
Influenza A(H7N9): Since the last FluWatch report, no new laboratory-confirmed cases of human infection with avian influenza A(H7N9) virus were reported by the World Health Organization. Globally to May 21, 2015, the WHO reported a total of 657 laboratory-confirmed human cases with avian influenza A(H7N9) virus, including 227 deaths. Documents related to the public health risk of influenza A(H7N9), as well as guidance for health professionals and advice for the public is updated regularly on the following websites:

Middle East Respiratory Syndrome Coronavirus (MERS-CoV)
Since the last FluWatch report, six new laboratory-confirmed cases of MERS-CoV have been reported by the World Health Organization. Globally, from September 2012 to May 21, 2015, the WHO has reported a total of 1,118 laboratory-confirmed cases of infection with MERS-CoV, including 423 deaths. All cases have either occurred in the Middle East or have had direct links to a primary case infected in the Middle East. The public health risk posed by MERS-CoV in Canada remains low (see the PHAC Assessment of Public Health Risk) and for the latest global risk assessment posted by the WHO on February 5, 2015: WHO MERS-CoV.

Documents related to the public health risk of MERS-CoV, as well as guidance for health professionals and advice for the public is updated regularly on the following websites:

International Influenza Reports


FluWatch definitions for the 2014-2015 season

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.

We would like to thank all the Fluwatch surveillance partners who are participating in this year's influenza surveillance program.

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