FluWatch report: May 3 to May 9, 2015 (Week 18)

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 18 (mostly in Central Canada and parts of British Columbia).
  • 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 18, 7,448 hospitalizations and 562 deaths have been reported from participating regions, which is more than were reported last year at this time (4,731 hospitalizations and 275 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: 2015-05-15

Influenza/ILI Activity (geographic spread)

In week 18, one region in BC and one region in NL reported widespread activity. Ten regions reported localized activity: BC(2), ON(6), and QC(2). Twenty-six regions reported sporadic activity: NT, BC, AB(5), SK(3), MB(4), ON, QC(4), NL, NB(5), and NS. Twenty regions reported no activity: YK, NT, NU(3), BC, MB, NL(2), NB(2), NS(8), and PE.

Figure 1. Map of overall influenza/ILI activity level by province and territory, Canada, Week 18

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 18, one region in BC and one region in NL reported widespread activity. Ten regions reported localized activity: BC(2), ON(6), and QC(2). Twenty-six regions reported sporadic activity: NT, BC, AB(5), SK(3), MB(4), ON, QC(4), NL, NB(5), and NS. Twenty regions reported no activity: YK, NT, NU(3), BC, MB, NL(2), NB(2), NS(8), and PE.

Influenza and Other Respiratory Virus Detections

The number of positive influenza tests decreased from 381 in week 17 to 299 in week 18. Influenza B remained the predominant virus in week 18, representing 89% 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 99.3% of those subtyped have been A(H3N2) (Table 1). To date this season, detailed information on age and type/subtype has been received for 36,794 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 381 in week 17 to 299 in week 18.

In week 18, detections for all other respiratory viruses except rhinovirus and human metapneumovirus decreased from the previous week (figure 3). The percent positive for rhinovirus increased from 13% in week 17 to 20% in week 18.

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 18, detections for all other respiratory viruses except rhinovirus and human metapneumovirus 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 3 to May 9, 2015) Cumulative (August 24, 2014 to May 9, 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 3 0 18 3522 28 2629 865 433
AB 1 0 0 1 31 3700 14 3531 155 912
SK 0 0 0 0 5 1314 0 839 475 286
MB 2 1 0 1 12 1124 1 390 733 197
ON 8 0 1 7 87 11157 4 4710 6399 1400
QC 16 0 0 16 83 11445 4 422 11019 3820
NB 0 0 0 0 19 1195 0 193 1002 524
NS 0 0 0 0 2 511 1 123 387 260
PE 0 0 0 0 0 131 1 128 2 108
NL 2 0 0 2 10 624 0 123 501 58
Canada 32 1 4 27 267 34723 97 13088 21538 7998
Percentage Footnote 2 10.7% 3.1% 12.5% 84.4% 89.3% 81.3% 0.3% 37.7% 62.0% 18.7%
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 3 to May 9, 2015 Cumulative (August 24, 2014 to May 9, 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 1 0 0 1 10 2092 22 809 1261 508 2600 7.1%
5-19 0 0 0 0 20 1783 6 957 820 751 2534 6.9%
20-44 3 0 0 3 25 3441 16 1671 1754 1018 4459 12.1%
45-64 6 0 0 6 39 3869 21 1658 2190 1705 5574 15.1%
65+ 9 0 0 9 78 18739 15 7286 11438 2761 21500 58.4%
Unknown 0 0 0 0 0 120 0 101 19 7 127 0.3%
Total 19 0 0 19 172 30044 80 12482 17482 6750 36794 100.0%
PercentageFootnote 2, 9.9% 0.0% 0.0% 100.0% 90.1% 81.7% 0.3% 41.5% 58.2% 18.3%    

Antiviral Resistance

During the 2014-2015 influenza season, the NML has tested 1,446 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 1,365 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) 890 1 888 0 1350 1349 (99.9%)
A (H1N1) 15 0 15 0 16 16 (100%)
B 541 1 541 0 NATable 3 - Footnote * NA Table 3 - Footnote *
TOTAL 1446 1 1446 0 1366 1365

Influenza Strain Characterizations

During the 2014-2015 influenza season, the National Microbiology Laboratory (NML) has characterized 849 influenza viruses [190 A(H3N2), 17 A(H1N1) and 642 influenza B].

Influenza A (H3N2): When tested by hemagglutination inhibition (HI) assay (n=190), one virus was antigenically similar to A/Texas/50/2012, five showed reduced titers to A/Texas/50/2012 and 184 were antigenically similar to A/Switzerland/9715293/2013, which is the influenza A(H3N2) component recommended for the 2015 Southern Hemisphere influenza vaccine. Additionally, 1,129 A(H3N2) viruses were unable to be tested by HI assay; however, sequence analysis showed that 1,127 belonged to a genetic group that typically shows reduced titers to A/Texas/50/2012.
Influenza A(H1N1):
Seventeen A(H1N1) viruses characterized were antigenically similar to A/California/7/2009.
Influenza B: Of the 642 influenza B viruses characterized, 602 viruses were antigenically similar to B/Massachusetts/2/2012, three viruses showed reduced titers against B/Massachusetts/2/2012, and 37 were B/Brisbane/60/2008-like (Figure 4).

Figure 4. Influenza strain characterizations, Canada, 2014-2015, N = 849

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.

The recommended components for the 2014-2015 northern hemisphere trivalent influenza vaccine include: an A/California/7/2009(H1N1)pdm09-like virus, an A/Texas/50/2012 (H3N2)-like virus, and a B/Massachusetts/2/2012-like virus (Yamagata lineage). For quadrivalent vaccines, the addition of a B/Brisbane/60/2008-like virus is recommended.

   Figure 4 Influenza strain characterizations, Canada, 2014-2015, N = 849 - 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 17 2%
A/Switzerland/97 15293/2013-like 184 22%
B/Massachusetts/2/2012-like 602 71%
reduced titres to B/Massachusetts/2/2012 3 0%
B/Brisbane/60/2008-like 37 4%

Influenza-like Illness (ILI) Consultation Rate

In week 18, the national influenza-like-illness (ILI) consultation rate increased from the previous week to 23.1 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 18, the national influenza-like-illness (ILI) consultation rate increased from the previous week to 23.1 consultations per 1,000.

Influenza Outbreak Surveillance

In week 18, 14 new outbreaks of influenza were reported: two due to influenza B, one due to influenza A and 11 for which the influenza type was not provided.  Eleven outbreaks were reported in long-term care facilities (LTCF) and three in institutional or community settings (Figure 6). To date this season, 1,265 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

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 18, six 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, three (50%) were <2 years of age and three (50%) were 2 to 9 years of age. One ICU case was reported.

To date this season, 681 hospitalizations have been reported by the IMPACT network, 509 (75%) 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, 86 cases were admitted to the ICU, of which 49 (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 9, 2015)
Influenza A B Influenza A and B
A Total A(H1) pdm09 A(H3) AFootnote (Uns) Total # (%)
0-5m 81 0 18 63 13 94 (13.8%)
6-23m 114 2 36 76 35 149 (21.9%)
2-4y 124 1 38 85 47 171 (25.1%)
5-9y 129 0 44 85 50 179 (26.3%)
10-16y 61 0 25 36 27 88 (12.9%)
Total 509 3 161 345 172 681
% Footnote 1 74.7% 0.6% 31.6% 67.8% 25.3% 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 4
6 9 8
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 6

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

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=681) ICU admissions(n=86)
0-5m 13.8% 3.5%
6-23m 21.9% 22.1%
2-4y 25.1% 30.2%
5-9y 26.3% 26.7%
10-16y 12.9% 17.4%

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 18, 78 laboratory-confirmed influenza-associated hospitalizations were reported from participating provinces and territoriesootnote *, which is lower than the number reported the previous week. Of the 78 hospitalizations, 46 (59%) were due to influenza A and 38 (49%) were in patients ≥65 years of age.

Since the start of the 2014-15 season, 7,448 hospitalizations have been reported; 6,510 (87%) with influenza A. Among cases for which the subtype of influenza A was reported, 99.3% were A(H3N2). The majority of cases (70%) were ≥65 years of age (Table 6). A total of 382 ICU admissions have been reported to date: 53% (n=202) were in adults ≥65 years of age and 34% (n=128) were in adults 20-64 years. A total of 562 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 512 adults ≥65 years of age. Influenza A has been reported in 92% 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 9 May, 2015)
Influenza A B Influenza A and B
A Total A(H1) pdm09 A(H3) AFootnote (Uns) Total # (%)
0-4 years 424 4 150 270 76 500 (7%)
5-19 years 256 0 118 138 86 342 (5%)
20-44 years 319 4 168 147 70 389 (5%)
45-64 years 711 11 347 353 185 896 (12%)
65+ years 4744 3 2260 2481 500 5244 (70%)
Unknown 56 1 52 3 21 77 (1%)
Total 6510 23 3095 3392 938 7448
Percentage Footnote 1 87.4% 0.4% 47.5% 52.1% 12.6% 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, six new laboratory-confirmed cases of human infection with avian influenza A(H7N9) virus were reported by the World Health Organization. Globally to May 14, 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, two new laboratory-confirmed cases of MERS-CoV have been reported by the World Health Organization. Globally, from September 2012 to May 14, 2015, the WHO has reported a total of 1,112 laboratory-confirmed cases of infection with MERS-CoV, including 422 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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