Re: Canada FluWatch Weekly Reports 2010-2011 Season Week 16 - 221 deaths total (excluding BC, QC, NB and NU)
<TABLE border=0 cellSpacing=0 cellPadding=0><TBODY><TR><TD>April 17 to 23, 2011 (Week 16)
</TD></TR></TBODY></TABLE>
Posted 2011-04-29
Overall Influenza Summary
Influenza Activity and Outbreaks
In week 16, 9 regions reported localized activity: ON(1), NB(2), NS(4), and NL(2); 28 regions reported sporadic activity (in BC(3), AB(5), SK(3), MB(3), ON(4), QC(6), NB(2), YK(1) and NU(1)) and 19 regions presented no activity (see Activity level Map). Compared to the previous week (week 15), 8 regions reported an increased level of influenza activity, 17 regions reported decreased activity, and 23 regions maintained a stable level of influenza activity (sporadic or higher). Fourteen new outbreaks were reported: 7 outbreaks of influenza in long-term care facilities (LTCF) in NS(5), NB(1) and NL(1); 1 outbreak of influenza in a hospital in NS; 5 ILI outbreaks in schools in NS(3), and NB(2); and one outbreak of ILI in another facility in NL.
Map of overall Influenza activity level by province and territory, Canada, Week 16
No Data
No Activity
Sporadic Activity
Localized Activity
Widespread Activity
Note: Influenza 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 (see graphs and tables) and reported outbreaks. Please refer to detailed definitions on the last page. For areas where no data is reported, late reports from these provinces and territories will appear on the FluWatch website.
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Number of influenza surveillance regions<SUP title="sub-regions within the province or territory as defined by the provincial/territorial epidemiologist. Graph may change as late returns come in">?</SUP> reporting widespread or localized influenza activity, Canada, by report week, 2010-2011 (N=56)
? sub-regions within the province or territory as defined by the provincial/territorial epidemiologist. Graph may change as late returns come in.
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Overall Number of Influenza Outbreaks, Canada, by Report Week, 2010-2011
Note that this was the first year that all the provinces and territories were reporting on influenza outbreaks in schools (greater than 10% absenteeism on any day most likely due to ILI) which has increased considerably the total number of outbreaks reported compared to previous years.
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ILI consultation rate
During week 16, the national ILI consultation rate was 16.7 consultations per 1,000 patient visits, which is decreased compared to the previous week and is within the expected rate for this time of year (see ILI graph). Children 5-19 years of age had the highest consultation rates (45.3 per 1,000 consultations), followed by children under 5 years of age (19.9 per 1,000 consultations) in week 16.
Influenza-like illness (ILI) consultation rates, Canada, by report week, 2010-2011 compared to 1996/97 through to 2008/09 seasons
Note: No data available for mean rate in previous years for weeks 19 to 39 (1996-1997 through 2002-2003 seasons). Delays in the reporting of data may cause data to change retrospectively.
Text Equivalent
Laboratory Surveillance Summary
The overall proportion of tests that were positive for influenza during week 16 was 7.2% (1.9% influenza A, 5.3% influenza B), which is decreased compared to week 15 (10.3%) and the third week in which more influenza B detections were reported than influenza A. The proportion of positive tests peaked in week 52 (see Influenza tests graph). Since the beginning of the season, 86.8% (16,320/18,810) of influenza virus detections have been influenza A viruses, of which 84.7% (5,446/6,431) of subtyped specimens have been A/H3N2. Detections of influenza B have been increasing steadily since week 03 and appear to have reached a peak in week 15. Among influenza A detections in week 16, 20 (36.4%) specimens were reported as influenza A/H3N2, 1 (1.8%) as pandemic H1N1 2009, and 34 (61.8%) as unsubtyped influenza A. Through detailed case-based laboratory reporting where age data is provided, since August 29, 2010, 50.8% (2049/4033) of cases with A/H3N2 were aged 65 years or older. In contrast, the majority of cases with pandemic H1N1 2009 (94.5%, 741/784) and influenza B (90.2%, 1246/1381) were under 65 years of age (see Tests detailed table). In week 16, the proportion of positive tests for respiratory syncytial virus detections (RSV) decreased to 9.2% of specimens tested. The proportion of positive RSV tests appears to have peaked in week 07. Since week 11, the proportion of positive tests for parainfluenza viruses has been increasing, reaching 5.8% in week 16, predominantly due to parainfluenza type 3 (51.4%) and type 1 (38.1%). (See Respiratory viruses graph).
Weekly & Cumulative numbers of positive influenza specimens by Provincial Laboratories, Canada, 2010-2011
<TABLE class=widthFull border=1 cellSpacing=0 cellPadding=2><TFOOT><TR><TD class=fontSize85 colSpan=13>* Unsubtyped: The specimen was typed as influenza A, but no test for subtyping was performed. Specimens from NT, YT, and NU are sent to reference laboratories in other provinces. Note: Cumulative data includes updates to previous weeks; due to reporting delays, the sum of weekly report totals do not add up to cumulative totals.
</TD></TR></TFOOT><TBODY><TR class=alignCenter><TH class=bg-colour-blue rowSpan=3 scope=col>Reporting provinces</TH><TH class="bg-colour-blue fontSize85" colSpan=6 scope=colgroup>Weekly (April 17 to April 23, 2011)</TH><TH class="bg-colour-blue fontSize85" colSpan=6 scope=colgroup>Cumulative (August 29, 2010 to April 23, 2011)</TH></TR><TR class=alignCenter><TH class="bg-colour-blue fontSize85" colSpan=5 scope=colgroup>Influenza A</TH><TH class="bg-colour-blue fontSize85" scope=col>B</TH><TH class="bg-colour-blue fontSize85" colSpan=5 scope=colgroup>Influenza A</TH><TH class=bg-colour-blue scope=col>B</TH></TR><TR class=alignCenter><TH class="fontSize85 bg-colour-blue" scope=col>A Total</TH><TH class="fontSize85 bg-colour-blue" scope=col>A(H1)</TH><TH class="fontSize85 bg-colour-blue" scope=col>A(H3)</TH><TH class="fontSize85 bg-colour-blue" scope=col>Pand H1N1</TH><TH class="fontSize85 bg-colour-blue noWrap" scope=col>A (Un S)*</TH><TH class="fontSize85 bg-colour-blue" scope=col>Total</TH><TH class="fontSize85 bg-colour-blue" scope=col>A Total</TH><TH class="fontSize85 bg-colour-blue" scope=col>A(H1)</TH><TH class="fontSize85 bg-colour-blue" scope=col>A(H3)</TH><TH class="fontSize85 bg-colour-blue" scope=col>Pand H1N1</TH><TH class="fontSize85 bg-colour-blue noWrap" scope=col>A (Un S)*</TH><TH class="fontSize85 bg-colour-blue" scope=col>Total</TH></TR><TR><TH class=bg-colour-blue scope=row>BC</TH><TD class=alignCenter>4</TD><TD class=alignCenter>0</TD><TD class=alignCenter>3</TD><TD class=alignCenter>1</TD><TD class=alignCenter>0</TD><TD class=alignCenter>1</TD><TD class=alignCenter>476</TD><TD class=alignCenter>0</TD><TD class=alignCenter>199</TD><TD class=alignCenter>164</TD><TD class=alignCenter>113</TD><TD class=alignCenter>176</TD></TR><TR><TH class=bg-colour-blue scope=row>AB</TH><TD class=alignCenter>10</TD><TD class=alignCenter>0</TD><TD class=alignCenter>7</TD><TD class=alignCenter>0</TD><TD class=alignCenter>3</TD><TD class=alignCenter>25</TD><TD class=alignCenter>1042</TD><TD class=alignCenter>0</TD><TD class=alignCenter>734</TD><TD class=alignCenter>270</TD><TD class=alignCenter>38</TD><TD class=alignCenter>687</TD></TR><TR><TH class=bg-colour-blue scope=row>SK</TH><TD class=alignCenter>2</TD><TD class=alignCenter>0</TD><TD class=alignCenter>1</TD><TD class=alignCenter>0</TD><TD class=alignCenter>1</TD><TD class=alignCenter>24</TD><TD class=alignCenter>313</TD><TD class=alignCenter>0</TD><TD class=alignCenter>210</TD><TD class=alignCenter>30</TD><TD class=alignCenter>73</TD><TD class=alignCenter>148</TD></TR><TR><TH class=bg-colour-blue scope=row>MB</TH><TD class=alignCenter>0</TD><TD class=alignCenter>0</TD><TD class=alignCenter>0</TD><TD class=alignCenter>0</TD><TD class=alignCenter>0</TD><TD class=alignCenter>3</TD><TD class=alignCenter>515</TD><TD class=alignCenter>0</TD><TD class=alignCenter>56</TD><TD class=alignCenter>2</TD><TD class=alignCenter>457</TD><TD class=alignCenter>12</TD></TR><TR><TH class=bg-colour-blue scope=row>ON</TH><TD class=alignCenter>5</TD><TD class=alignCenter>0</TD><TD class=alignCenter>2</TD><TD class=alignCenter>0</TD><TD class=alignCenter>3</TD><TD class=alignCenter>39</TD><TD class=alignCenter>6874</TD><TD class=alignCenter>0</TD><TD class=alignCenter>2435</TD><TD class=alignCenter>272</TD><TD class=alignCenter>4167</TD><TD class=alignCenter>779</TD></TR><TR><TH class=bg-colour-blue scope=row>QC</TH><TD class=alignCenter>16</TD><TD class=alignCenter>0</TD><TD class=alignCenter>0</TD><TD class=alignCenter>0</TD><TD class=alignCenter>16</TD><TD class=alignCenter>51</TD><TD class=alignCenter>5616</TD><TD class=alignCenter>0</TD><TD class=alignCenter>877</TD><TD class=alignCenter>38</TD><TD class=alignCenter>4701</TD><TD class=alignCenter>595</TD></TR><TR><TH class=bg-colour-blue scope=row>NB</TH><TD class=alignCenter>6</TD><TD class=alignCenter>0</TD><TD class=alignCenter>5</TD><TD class=alignCenter>0</TD><TD class=alignCenter>1</TD><TD class=alignCenter>6</TD><TD class=alignCenter>943</TD><TD class=alignCenter>0</TD><TD class=alignCenter>662</TD><TD class=alignCenter>176</TD><TD class=alignCenter>105</TD><TD class=alignCenter>68</TD></TR><TR><TH class=bg-colour-blue scope=row>NS</TH><TD class=alignCenter>5</TD><TD class=alignCenter>0</TD><TD class=alignCenter>2</TD><TD class=alignCenter>0</TD><TD class=alignCenter>3</TD><TD class=alignCenter>0</TD><TD class=alignCenter>257</TD><TD class=alignCenter>0</TD><TD class=alignCenter>80</TD><TD class=alignCenter>11</TD><TD class=alignCenter>166</TD><TD class=alignCenter>3</TD></TR><TR><TH class=bg-colour-blue scope=row>PE</TH><TD class=alignCenter>0</TD><TD class=alignCenter>0</TD><TD class=alignCenter>0</TD><TD class=alignCenter>0</TD><TD class=alignCenter>0</TD><TD class=alignCenter>0</TD><TD class=alignCenter>97</TD><TD class=alignCenter>0</TD><TD class=alignCenter>79</TD><TD class=alignCenter>16</TD><TD class=alignCenter>2</TD><TD class=alignCenter>6</TD></TR><TR><TH class=bg-colour-blue scope=row>NL</TH><TD class=alignCenter>7</TD><TD class=alignCenter>0</TD><TD class=alignCenter>0</TD><TD class=alignCenter>0</TD><TD class=alignCenter>7</TD><TD class=alignCenter>8</TD><TD class=alignCenter>187</TD><TD class=alignCenter>0</TD><TD class=alignCenter>114</TD><TD class=alignCenter>6</TD><TD class=alignCenter>67</TD><TD class=alignCenter>16</TD></TR><TR><TH class=bg-colour-blue scope=row>Canada</TH><TD class=alignCenter>55</TD><TD class=alignCenter>0</TD><TD class=alignCenter>20</TD><TD class=alignCenter>1</TD><TD class=alignCenter>34</TD><TD class=alignCenter>157</TD><TD class=alignCenter>16320</TD><TD class=alignCenter>0</TD><TD class=alignCenter>5446</TD><TD class=alignCenter>985</TD><TD class=alignCenter>9889</TD><TD class=alignCenter>2490</TD></TR></TBODY></TABLE>
Weekly & Cumulative numbers of positive influenza specimens by age groups reported through case-based laboratory reporting, Canada, 2010-2011*
<TABLE class=widthFull border=1 cellSpacing=0 cellPadding=2><TFOOT><TR><TD class=fontSize85 colSpan=11> * Please note that this table reflects the number of specimens for which demographic information was reported. These represent a subset of all positive influenza cases reported. Five provinces have reported detailed case-by-case data since the beginning of the season (BC, AB, SK, MB and ON). Delays in the reporting of data may cause data to change retrospectively.
</TD></TR></TFOOT><TBODY><TR class=bg-colour-yellow><TH rowSpan=3 scope=col>Age groups</TH><TH colSpan=5 scope=colgroup>Weekly
(April 17 to April 23, 2011)</TH><TH colSpan=5 scope=colgroup>Cumulative
(Aug. 29, 2010 to Apr. 23, 2011)
</TH></TR><TR class=bg-colour-yellow><TH colSpan=4 scope=colgroup>Influenza A</TH><TH>B</TH><TH colSpan=4 scope=colgroup>Influenza A</TH><TH>B</TH></TR><TR class=bg-colour-yellow><TH scope=col>A Total</TH><TH scope=col>Pandemic H1N1</TH><TH scope=col>A/H3N2</TH><TH scope=col>A unsubtyped</TH><TH scope=col>Total</TH><TH scope=col>A Total</TH><TH scope=col>Pandemic H1N1</TH><TH scope=col>A/H3N2</TH><TH scope=col>A unsubtyped</TH><TH scope=col>Total</TH></TR><TR><TD><5</TD><TD class=alignCenter>2</TD><TD class=alignCenter>0</TD><TD class=alignCenter>1</TD><TD class=alignCenter>1</TD><TD class=alignCenter>10</TD><TD class=alignCenter>999</TD><TD class=alignCenter>126</TD><TD class=alignCenter>728</TD><TD class=alignCenter>145</TD><TD class=alignCenter>367</TD></TR><TR><TD>5-19</TD><TD class=alignCenter>1</TD><TD class=alignCenter>0</TD><TD class=alignCenter>0</TD><TD class=alignCenter>1</TD><TD class=alignCenter>7</TD><TD class=alignCenter>517</TD><TD class=alignCenter>103</TD><TD class=alignCenter>296</TD><TD class=alignCenter>118</TD><TD class=alignCenter>499</TD></TR><TR><TD>20-44</TD><TD class=alignCenter>2</TD><TD class=alignCenter>0</TD><TD class=alignCenter>1</TD><TD class=alignCenter>1</TD><TD class=alignCenter>5</TD><TD class=alignCenter>1071</TD><TD class=alignCenter>327</TD><TD class=alignCenter>528</TD><TD class=alignCenter>216</TD><TD class=alignCenter>270</TD></TR><TR><TD>45-64</TD><TD class=alignCenter>2</TD><TD class=alignCenter>0</TD><TD class=alignCenter>1</TD><TD class=alignCenter>1</TD><TD class=alignCenter>0</TD><TD class=alignCenter>785</TD><TD class=alignCenter>185</TD><TD class=alignCenter>432</TD><TD class=alignCenter>168</TD><TD class=alignCenter>110</TD></TR><TR><TD>65+</TD><TD class=alignCenter>5</TD><TD class=alignCenter>0</TD><TD class=alignCenter>3</TD><TD class=alignCenter>2</TD><TD class=alignCenter>1</TD><TD class=alignCenter>2484</TD><TD class=alignCenter>43</TD><TD class=alignCenter>2049</TD><TD class=alignCenter>392</TD><TD class=alignCenter>135</TD></TR><TR><TD>Unknown</TD><TD class=alignCenter>2</TD><TD class=alignCenter>0</TD><TD class=alignCenter>0</TD><TD class=alignCenter>2</TD><TD class=alignCenter>1</TD><TD class=alignCenter>231</TD><TD class=alignCenter>3</TD><TD class=alignCenter>224</TD><TD class=alignCenter>4</TD><TD class=alignCenter>1</TD></TR><TR><TD>Total</TD><TD class=alignCenter>14</TD><TD class=alignCenter>0</TD><TD class=alignCenter>6</TD><TD class=alignCenter>8</TD><TD class=alignCenter>24</TD><TD class=alignCenter>6087</TD><TD class=alignCenter>787</TD><TD class=alignCenter>4257</TD><TD class=alignCenter>1043</TD><TD class=alignCenter>1382</TD></TR></TBODY></TABLE>
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Influenza tests reported and percentage of tests positive, Canada, by report week, 2010-2011
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Percent positive influenza tests, compared to other respiratory viruses, Canada, by reporting week, 2010-2011
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Canadian situation
Antigenic Characterization
Between September 1 and April 28, 2011, the National Microbiology Laboratory (NML) has antigenically characterized 804 influenza viruses that were received from provincial laboratories: 252 A/H3N2, 137 pandemic H1N1 2009 and 415 B viruses. Of the 252 influenza A/H3N2 viruses characterized, 249 (98.8%) were antigenically related to A/Perth/16/2009, which is the influenza A/H3N2 component recommended for the 2010-11 influenza vaccine. Three viruses (1.2%) tested showed reduced titer with antiserum produced against A/Perth/16/2009. Of the 137 pandemic H1N1 2009 viruses characterized, 136 (99.3%) were antigenically related to the pandemic vaccine virus A/California/7/2009, which is the recommended H1N1 component for the 2010-11 influenza vaccine. One virus (0.7%) tested showed reduced titer with antiserum produced against A/California/7/2009. Of the 415 influenza B viruses characterized, 396 (95.4%) were antigenically related to B/Brisbane/60/08 (Victoria lineage), which is the recommended influenza B component for the 2010-11 influenza vaccine. Four of the 396 viruses tested showed reduced titer with antisera produced against B/Brisbane/60/08. Nineteen (4.6%) influenza B viruses were characterized as B/Wisconsin/01/2010-like, which belongs to the Yamagata lineage. B/Wisconsin/01/2010-like viruses are antigenically and genetically different from the previous Yamagata lineage vaccine strain B/Florida/04/2006.
Antiviral Resistance
Since the beginning of the 2010-2011 season, NML has tested 591 influenza A isolates (445 A/H3N2 and 146 pandemic H1N1 2009) for amantadine resistance and found that 444 influenza A/H3N2 were resistant and one was sensitive. All 146 influenza A/H1N1 viruses were resistant to amantadine. Of 643 influenza viruses (228 A/H3N2, 124 pandemic H1N1 2009, and 291 influenza B) tested for resistance to oseltamivir, 227 A/H3N2 viruses were sensitive and one was resistant with E119V mutation. The resistant case was associated with oseltamivir prophylaxis/treatment. Of the 124 pandemic H1N1 2009 isolates tested for oseltamivir resistance, 123 were sensitive and one was resistant with the H275Y mutation. The resistant case was associated with oseltamivir treatment. All 291 B viruses were sensitive to oseltamivir. Of 633 influenza viruses (224 A/H3N2, 121 pandemic H1N1 2009, and 288 influenza B) tested for zanamivir resistance all isolates were found to be sensitive.
Severe Illness Surveillance
Paediatric Influenza Hospitalizations and Deaths
In week 16, 7 new laboratory-confirmed influenza-associated paediatric (16 years of age and under) hospitalizations were reported through the Immunization Monitoring Program Active (IMPACT) network: 2 from AB, 2 from SK and 3 from QC. This number is similar to the previous week (week 15) in which 6 paediatric hospitalizations were reported (note that numbers may fluctuate because of the delays in reporting). Five paediatric deaths have been reported via IMPACT this season all with underlying comorbidities.
Since the beginning of the season, 632 hospitalizations with laboratory-confirmed influenza have been reported: 102 (16.1%) as influenza A/H3N2, 22 (3.5%) pandemic H1N1 2009, 327 (51.7%) as unsubytped influenza A, and 181 (28.6%) influenza B. The distribution of cases to date by age group was as follows: 16.8% among 0-5 month olds; 28.2% among 6-23 month olds; 28.8% among the 2-4 year-olds; 15.3% among 5-9 year-olds; and 10.9% among children 10-16 years old.
Adult Influenza Hospitalizations and Deaths
During week 16, 4 new hospitalizations with laboratory-confirmed influenza among adults (16 years of age and older) were reported through the Canadian Nosocomial Infection Surveillance Program (CNISP), 3 influenza B and 1 influenza A/H3N2. This number is similar to the 5 cases reported in week 15 (note that numbers may fluctuate because of the delays in reporting). Since the beginning of the season, 952 hospitalized cases have been reported: 202 (21.2%) A/H3N2, 45 (4.7%) pandemic H1N1 2009, 640 (67.2%) influenza A unsubtyped, and 65 (6.8%) influenza B, from all reporting provinces. To date, 642 of the 952 (67.4%) cases were aged 65 years or older and 430 (45.2%) were males.
Aggregate Influenza Hospitalizations and Deaths
Nine provinces and territories (excluding BC, QC, NB and NU) currently conduct severe outcomes surveillance and report weekly numbers of hospitalizations, ICU admissions and deaths with laboratory-confirmed influenza. In week 16, no deaths with influenza were reported. Among the 221 fatal cases reported since the beginning of the influenza season, influenza A/H3N2 was identified in 61.1% (135/221), unsubtyped influenza A in 28.5% (63/221), pandemic H1N1 2009 in 5.9% (13/221), and influenza B in 4.5% (10/221). Eighty percent (176/221) of these fatal cases were among persons 65 years of age or older, and another 11% (24/221) were between the ages of 45 and 64 years old, in keeping with the age-groups usually affected by A/H3N2. (Note that numbers may fluctuate because of the delays in reporting).
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<TABLE border=0 cellSpacing=0 cellPadding=0><TBODY><TR><TD>April 17 to 23, 2011 (Week 16)
</TD></TR></TBODY></TABLE>
Posted 2011-04-29
Overall Influenza Summary
- In week 16, influenza activity in Canada continues to decline.
- The overall percentage of influenza positive specimens continues to decrease.
- Fewer regions reported localized influenza activity this week compared to the previous week although slightly more outbreaks were reported, all in the Atlantic provinces.
- The ILI consultation rate decreased, and both adult and paediatric hospitalizations with influenza were similar to the previous week.
Influenza Activity and Outbreaks
In week 16, 9 regions reported localized activity: ON(1), NB(2), NS(4), and NL(2); 28 regions reported sporadic activity (in BC(3), AB(5), SK(3), MB(3), ON(4), QC(6), NB(2), YK(1) and NU(1)) and 19 regions presented no activity (see Activity level Map). Compared to the previous week (week 15), 8 regions reported an increased level of influenza activity, 17 regions reported decreased activity, and 23 regions maintained a stable level of influenza activity (sporadic or higher). Fourteen new outbreaks were reported: 7 outbreaks of influenza in long-term care facilities (LTCF) in NS(5), NB(1) and NL(1); 1 outbreak of influenza in a hospital in NS; 5 ILI outbreaks in schools in NS(3), and NB(2); and one outbreak of ILI in another facility in NL.
Map of overall Influenza activity level by province and territory, Canada, Week 16
No Data
No Activity
Sporadic Activity
Localized Activity
Widespread Activity
Note: Influenza 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 (see graphs and tables) and reported outbreaks. Please refer to detailed definitions on the last page. For areas where no data is reported, late reports from these provinces and territories will appear on the FluWatch website.
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Number of influenza surveillance regions<SUP title="sub-regions within the province or territory as defined by the provincial/territorial epidemiologist. Graph may change as late returns come in">?</SUP> reporting widespread or localized influenza activity, Canada, by report week, 2010-2011 (N=56)
? sub-regions within the province or territory as defined by the provincial/territorial epidemiologist. Graph may change as late returns come in.
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Overall Number of Influenza Outbreaks, Canada, by Report Week, 2010-2011
Note that this was the first year that all the provinces and territories were reporting on influenza outbreaks in schools (greater than 10% absenteeism on any day most likely due to ILI) which has increased considerably the total number of outbreaks reported compared to previous years.
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ILI consultation rate
During week 16, the national ILI consultation rate was 16.7 consultations per 1,000 patient visits, which is decreased compared to the previous week and is within the expected rate for this time of year (see ILI graph). Children 5-19 years of age had the highest consultation rates (45.3 per 1,000 consultations), followed by children under 5 years of age (19.9 per 1,000 consultations) in week 16.
Influenza-like illness (ILI) consultation rates, Canada, by report week, 2010-2011 compared to 1996/97 through to 2008/09 seasons
Note: No data available for mean rate in previous years for weeks 19 to 39 (1996-1997 through 2002-2003 seasons). Delays in the reporting of data may cause data to change retrospectively.
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Laboratory Surveillance Summary
The overall proportion of tests that were positive for influenza during week 16 was 7.2% (1.9% influenza A, 5.3% influenza B), which is decreased compared to week 15 (10.3%) and the third week in which more influenza B detections were reported than influenza A. The proportion of positive tests peaked in week 52 (see Influenza tests graph). Since the beginning of the season, 86.8% (16,320/18,810) of influenza virus detections have been influenza A viruses, of which 84.7% (5,446/6,431) of subtyped specimens have been A/H3N2. Detections of influenza B have been increasing steadily since week 03 and appear to have reached a peak in week 15. Among influenza A detections in week 16, 20 (36.4%) specimens were reported as influenza A/H3N2, 1 (1.8%) as pandemic H1N1 2009, and 34 (61.8%) as unsubtyped influenza A. Through detailed case-based laboratory reporting where age data is provided, since August 29, 2010, 50.8% (2049/4033) of cases with A/H3N2 were aged 65 years or older. In contrast, the majority of cases with pandemic H1N1 2009 (94.5%, 741/784) and influenza B (90.2%, 1246/1381) were under 65 years of age (see Tests detailed table). In week 16, the proportion of positive tests for respiratory syncytial virus detections (RSV) decreased to 9.2% of specimens tested. The proportion of positive RSV tests appears to have peaked in week 07. Since week 11, the proportion of positive tests for parainfluenza viruses has been increasing, reaching 5.8% in week 16, predominantly due to parainfluenza type 3 (51.4%) and type 1 (38.1%). (See Respiratory viruses graph).
Weekly & Cumulative numbers of positive influenza specimens by Provincial Laboratories, Canada, 2010-2011
<TABLE class=widthFull border=1 cellSpacing=0 cellPadding=2><TFOOT><TR><TD class=fontSize85 colSpan=13>* Unsubtyped: The specimen was typed as influenza A, but no test for subtyping was performed. Specimens from NT, YT, and NU are sent to reference laboratories in other provinces. Note: Cumulative data includes updates to previous weeks; due to reporting delays, the sum of weekly report totals do not add up to cumulative totals.
</TD></TR></TFOOT><TBODY><TR class=alignCenter><TH class=bg-colour-blue rowSpan=3 scope=col>Reporting provinces</TH><TH class="bg-colour-blue fontSize85" colSpan=6 scope=colgroup>Weekly (April 17 to April 23, 2011)</TH><TH class="bg-colour-blue fontSize85" colSpan=6 scope=colgroup>Cumulative (August 29, 2010 to April 23, 2011)</TH></TR><TR class=alignCenter><TH class="bg-colour-blue fontSize85" colSpan=5 scope=colgroup>Influenza A</TH><TH class="bg-colour-blue fontSize85" scope=col>B</TH><TH class="bg-colour-blue fontSize85" colSpan=5 scope=colgroup>Influenza A</TH><TH class=bg-colour-blue scope=col>B</TH></TR><TR class=alignCenter><TH class="fontSize85 bg-colour-blue" scope=col>A Total</TH><TH class="fontSize85 bg-colour-blue" scope=col>A(H1)</TH><TH class="fontSize85 bg-colour-blue" scope=col>A(H3)</TH><TH class="fontSize85 bg-colour-blue" scope=col>Pand H1N1</TH><TH class="fontSize85 bg-colour-blue noWrap" scope=col>A (Un S)*</TH><TH class="fontSize85 bg-colour-blue" scope=col>Total</TH><TH class="fontSize85 bg-colour-blue" scope=col>A Total</TH><TH class="fontSize85 bg-colour-blue" scope=col>A(H1)</TH><TH class="fontSize85 bg-colour-blue" scope=col>A(H3)</TH><TH class="fontSize85 bg-colour-blue" scope=col>Pand H1N1</TH><TH class="fontSize85 bg-colour-blue noWrap" scope=col>A (Un S)*</TH><TH class="fontSize85 bg-colour-blue" scope=col>Total</TH></TR><TR><TH class=bg-colour-blue scope=row>BC</TH><TD class=alignCenter>4</TD><TD class=alignCenter>0</TD><TD class=alignCenter>3</TD><TD class=alignCenter>1</TD><TD class=alignCenter>0</TD><TD class=alignCenter>1</TD><TD class=alignCenter>476</TD><TD class=alignCenter>0</TD><TD class=alignCenter>199</TD><TD class=alignCenter>164</TD><TD class=alignCenter>113</TD><TD class=alignCenter>176</TD></TR><TR><TH class=bg-colour-blue scope=row>AB</TH><TD class=alignCenter>10</TD><TD class=alignCenter>0</TD><TD class=alignCenter>7</TD><TD class=alignCenter>0</TD><TD class=alignCenter>3</TD><TD class=alignCenter>25</TD><TD class=alignCenter>1042</TD><TD class=alignCenter>0</TD><TD class=alignCenter>734</TD><TD class=alignCenter>270</TD><TD class=alignCenter>38</TD><TD class=alignCenter>687</TD></TR><TR><TH class=bg-colour-blue scope=row>SK</TH><TD class=alignCenter>2</TD><TD class=alignCenter>0</TD><TD class=alignCenter>1</TD><TD class=alignCenter>0</TD><TD class=alignCenter>1</TD><TD class=alignCenter>24</TD><TD class=alignCenter>313</TD><TD class=alignCenter>0</TD><TD class=alignCenter>210</TD><TD class=alignCenter>30</TD><TD class=alignCenter>73</TD><TD class=alignCenter>148</TD></TR><TR><TH class=bg-colour-blue scope=row>MB</TH><TD class=alignCenter>0</TD><TD class=alignCenter>0</TD><TD class=alignCenter>0</TD><TD class=alignCenter>0</TD><TD class=alignCenter>0</TD><TD class=alignCenter>3</TD><TD class=alignCenter>515</TD><TD class=alignCenter>0</TD><TD class=alignCenter>56</TD><TD class=alignCenter>2</TD><TD class=alignCenter>457</TD><TD class=alignCenter>12</TD></TR><TR><TH class=bg-colour-blue scope=row>ON</TH><TD class=alignCenter>5</TD><TD class=alignCenter>0</TD><TD class=alignCenter>2</TD><TD class=alignCenter>0</TD><TD class=alignCenter>3</TD><TD class=alignCenter>39</TD><TD class=alignCenter>6874</TD><TD class=alignCenter>0</TD><TD class=alignCenter>2435</TD><TD class=alignCenter>272</TD><TD class=alignCenter>4167</TD><TD class=alignCenter>779</TD></TR><TR><TH class=bg-colour-blue scope=row>QC</TH><TD class=alignCenter>16</TD><TD class=alignCenter>0</TD><TD class=alignCenter>0</TD><TD class=alignCenter>0</TD><TD class=alignCenter>16</TD><TD class=alignCenter>51</TD><TD class=alignCenter>5616</TD><TD class=alignCenter>0</TD><TD class=alignCenter>877</TD><TD class=alignCenter>38</TD><TD class=alignCenter>4701</TD><TD class=alignCenter>595</TD></TR><TR><TH class=bg-colour-blue scope=row>NB</TH><TD class=alignCenter>6</TD><TD class=alignCenter>0</TD><TD class=alignCenter>5</TD><TD class=alignCenter>0</TD><TD class=alignCenter>1</TD><TD class=alignCenter>6</TD><TD class=alignCenter>943</TD><TD class=alignCenter>0</TD><TD class=alignCenter>662</TD><TD class=alignCenter>176</TD><TD class=alignCenter>105</TD><TD class=alignCenter>68</TD></TR><TR><TH class=bg-colour-blue scope=row>NS</TH><TD class=alignCenter>5</TD><TD class=alignCenter>0</TD><TD class=alignCenter>2</TD><TD class=alignCenter>0</TD><TD class=alignCenter>3</TD><TD class=alignCenter>0</TD><TD class=alignCenter>257</TD><TD class=alignCenter>0</TD><TD class=alignCenter>80</TD><TD class=alignCenter>11</TD><TD class=alignCenter>166</TD><TD class=alignCenter>3</TD></TR><TR><TH class=bg-colour-blue scope=row>PE</TH><TD class=alignCenter>0</TD><TD class=alignCenter>0</TD><TD class=alignCenter>0</TD><TD class=alignCenter>0</TD><TD class=alignCenter>0</TD><TD class=alignCenter>0</TD><TD class=alignCenter>97</TD><TD class=alignCenter>0</TD><TD class=alignCenter>79</TD><TD class=alignCenter>16</TD><TD class=alignCenter>2</TD><TD class=alignCenter>6</TD></TR><TR><TH class=bg-colour-blue scope=row>NL</TH><TD class=alignCenter>7</TD><TD class=alignCenter>0</TD><TD class=alignCenter>0</TD><TD class=alignCenter>0</TD><TD class=alignCenter>7</TD><TD class=alignCenter>8</TD><TD class=alignCenter>187</TD><TD class=alignCenter>0</TD><TD class=alignCenter>114</TD><TD class=alignCenter>6</TD><TD class=alignCenter>67</TD><TD class=alignCenter>16</TD></TR><TR><TH class=bg-colour-blue scope=row>Canada</TH><TD class=alignCenter>55</TD><TD class=alignCenter>0</TD><TD class=alignCenter>20</TD><TD class=alignCenter>1</TD><TD class=alignCenter>34</TD><TD class=alignCenter>157</TD><TD class=alignCenter>16320</TD><TD class=alignCenter>0</TD><TD class=alignCenter>5446</TD><TD class=alignCenter>985</TD><TD class=alignCenter>9889</TD><TD class=alignCenter>2490</TD></TR></TBODY></TABLE>
Weekly & Cumulative numbers of positive influenza specimens by age groups reported through case-based laboratory reporting, Canada, 2010-2011*
<TABLE class=widthFull border=1 cellSpacing=0 cellPadding=2><TFOOT><TR><TD class=fontSize85 colSpan=11> * Please note that this table reflects the number of specimens for which demographic information was reported. These represent a subset of all positive influenza cases reported. Five provinces have reported detailed case-by-case data since the beginning of the season (BC, AB, SK, MB and ON). Delays in the reporting of data may cause data to change retrospectively.
</TD></TR></TFOOT><TBODY><TR class=bg-colour-yellow><TH rowSpan=3 scope=col>Age groups</TH><TH colSpan=5 scope=colgroup>Weekly
(April 17 to April 23, 2011)</TH><TH colSpan=5 scope=colgroup>Cumulative
(Aug. 29, 2010 to Apr. 23, 2011)
</TH></TR><TR class=bg-colour-yellow><TH colSpan=4 scope=colgroup>Influenza A</TH><TH>B</TH><TH colSpan=4 scope=colgroup>Influenza A</TH><TH>B</TH></TR><TR class=bg-colour-yellow><TH scope=col>A Total</TH><TH scope=col>Pandemic H1N1</TH><TH scope=col>A/H3N2</TH><TH scope=col>A unsubtyped</TH><TH scope=col>Total</TH><TH scope=col>A Total</TH><TH scope=col>Pandemic H1N1</TH><TH scope=col>A/H3N2</TH><TH scope=col>A unsubtyped</TH><TH scope=col>Total</TH></TR><TR><TD><5</TD><TD class=alignCenter>2</TD><TD class=alignCenter>0</TD><TD class=alignCenter>1</TD><TD class=alignCenter>1</TD><TD class=alignCenter>10</TD><TD class=alignCenter>999</TD><TD class=alignCenter>126</TD><TD class=alignCenter>728</TD><TD class=alignCenter>145</TD><TD class=alignCenter>367</TD></TR><TR><TD>5-19</TD><TD class=alignCenter>1</TD><TD class=alignCenter>0</TD><TD class=alignCenter>0</TD><TD class=alignCenter>1</TD><TD class=alignCenter>7</TD><TD class=alignCenter>517</TD><TD class=alignCenter>103</TD><TD class=alignCenter>296</TD><TD class=alignCenter>118</TD><TD class=alignCenter>499</TD></TR><TR><TD>20-44</TD><TD class=alignCenter>2</TD><TD class=alignCenter>0</TD><TD class=alignCenter>1</TD><TD class=alignCenter>1</TD><TD class=alignCenter>5</TD><TD class=alignCenter>1071</TD><TD class=alignCenter>327</TD><TD class=alignCenter>528</TD><TD class=alignCenter>216</TD><TD class=alignCenter>270</TD></TR><TR><TD>45-64</TD><TD class=alignCenter>2</TD><TD class=alignCenter>0</TD><TD class=alignCenter>1</TD><TD class=alignCenter>1</TD><TD class=alignCenter>0</TD><TD class=alignCenter>785</TD><TD class=alignCenter>185</TD><TD class=alignCenter>432</TD><TD class=alignCenter>168</TD><TD class=alignCenter>110</TD></TR><TR><TD>65+</TD><TD class=alignCenter>5</TD><TD class=alignCenter>0</TD><TD class=alignCenter>3</TD><TD class=alignCenter>2</TD><TD class=alignCenter>1</TD><TD class=alignCenter>2484</TD><TD class=alignCenter>43</TD><TD class=alignCenter>2049</TD><TD class=alignCenter>392</TD><TD class=alignCenter>135</TD></TR><TR><TD>Unknown</TD><TD class=alignCenter>2</TD><TD class=alignCenter>0</TD><TD class=alignCenter>0</TD><TD class=alignCenter>2</TD><TD class=alignCenter>1</TD><TD class=alignCenter>231</TD><TD class=alignCenter>3</TD><TD class=alignCenter>224</TD><TD class=alignCenter>4</TD><TD class=alignCenter>1</TD></TR><TR><TD>Total</TD><TD class=alignCenter>14</TD><TD class=alignCenter>0</TD><TD class=alignCenter>6</TD><TD class=alignCenter>8</TD><TD class=alignCenter>24</TD><TD class=alignCenter>6087</TD><TD class=alignCenter>787</TD><TD class=alignCenter>4257</TD><TD class=alignCenter>1043</TD><TD class=alignCenter>1382</TD></TR></TBODY></TABLE>
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Influenza tests reported and percentage of tests positive, Canada, by report week, 2010-2011
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Percent positive influenza tests, compared to other respiratory viruses, Canada, by reporting week, 2010-2011
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Canadian situation
Antigenic Characterization
Between September 1 and April 28, 2011, the National Microbiology Laboratory (NML) has antigenically characterized 804 influenza viruses that were received from provincial laboratories: 252 A/H3N2, 137 pandemic H1N1 2009 and 415 B viruses. Of the 252 influenza A/H3N2 viruses characterized, 249 (98.8%) were antigenically related to A/Perth/16/2009, which is the influenza A/H3N2 component recommended for the 2010-11 influenza vaccine. Three viruses (1.2%) tested showed reduced titer with antiserum produced against A/Perth/16/2009. Of the 137 pandemic H1N1 2009 viruses characterized, 136 (99.3%) were antigenically related to the pandemic vaccine virus A/California/7/2009, which is the recommended H1N1 component for the 2010-11 influenza vaccine. One virus (0.7%) tested showed reduced titer with antiserum produced against A/California/7/2009. Of the 415 influenza B viruses characterized, 396 (95.4%) were antigenically related to B/Brisbane/60/08 (Victoria lineage), which is the recommended influenza B component for the 2010-11 influenza vaccine. Four of the 396 viruses tested showed reduced titer with antisera produced against B/Brisbane/60/08. Nineteen (4.6%) influenza B viruses were characterized as B/Wisconsin/01/2010-like, which belongs to the Yamagata lineage. B/Wisconsin/01/2010-like viruses are antigenically and genetically different from the previous Yamagata lineage vaccine strain B/Florida/04/2006.
Antiviral Resistance
Since the beginning of the 2010-2011 season, NML has tested 591 influenza A isolates (445 A/H3N2 and 146 pandemic H1N1 2009) for amantadine resistance and found that 444 influenza A/H3N2 were resistant and one was sensitive. All 146 influenza A/H1N1 viruses were resistant to amantadine. Of 643 influenza viruses (228 A/H3N2, 124 pandemic H1N1 2009, and 291 influenza B) tested for resistance to oseltamivir, 227 A/H3N2 viruses were sensitive and one was resistant with E119V mutation. The resistant case was associated with oseltamivir prophylaxis/treatment. Of the 124 pandemic H1N1 2009 isolates tested for oseltamivir resistance, 123 were sensitive and one was resistant with the H275Y mutation. The resistant case was associated with oseltamivir treatment. All 291 B viruses were sensitive to oseltamivir. Of 633 influenza viruses (224 A/H3N2, 121 pandemic H1N1 2009, and 288 influenza B) tested for zanamivir resistance all isolates were found to be sensitive.
Severe Illness Surveillance
Paediatric Influenza Hospitalizations and Deaths
In week 16, 7 new laboratory-confirmed influenza-associated paediatric (16 years of age and under) hospitalizations were reported through the Immunization Monitoring Program Active (IMPACT) network: 2 from AB, 2 from SK and 3 from QC. This number is similar to the previous week (week 15) in which 6 paediatric hospitalizations were reported (note that numbers may fluctuate because of the delays in reporting). Five paediatric deaths have been reported via IMPACT this season all with underlying comorbidities.
Since the beginning of the season, 632 hospitalizations with laboratory-confirmed influenza have been reported: 102 (16.1%) as influenza A/H3N2, 22 (3.5%) pandemic H1N1 2009, 327 (51.7%) as unsubytped influenza A, and 181 (28.6%) influenza B. The distribution of cases to date by age group was as follows: 16.8% among 0-5 month olds; 28.2% among 6-23 month olds; 28.8% among the 2-4 year-olds; 15.3% among 5-9 year-olds; and 10.9% among children 10-16 years old.
Adult Influenza Hospitalizations and Deaths
During week 16, 4 new hospitalizations with laboratory-confirmed influenza among adults (16 years of age and older) were reported through the Canadian Nosocomial Infection Surveillance Program (CNISP), 3 influenza B and 1 influenza A/H3N2. This number is similar to the 5 cases reported in week 15 (note that numbers may fluctuate because of the delays in reporting). Since the beginning of the season, 952 hospitalized cases have been reported: 202 (21.2%) A/H3N2, 45 (4.7%) pandemic H1N1 2009, 640 (67.2%) influenza A unsubtyped, and 65 (6.8%) influenza B, from all reporting provinces. To date, 642 of the 952 (67.4%) cases were aged 65 years or older and 430 (45.2%) were males.
Aggregate Influenza Hospitalizations and Deaths
Nine provinces and territories (excluding BC, QC, NB and NU) currently conduct severe outcomes surveillance and report weekly numbers of hospitalizations, ICU admissions and deaths with laboratory-confirmed influenza. In week 16, no deaths with influenza were reported. Among the 221 fatal cases reported since the beginning of the influenza season, influenza A/H3N2 was identified in 61.1% (135/221), unsubtyped influenza A in 28.5% (63/221), pandemic H1N1 2009 in 5.9% (13/221), and influenza B in 4.5% (10/221). Eighty percent (176/221) of these fatal cases were among persons 65 years of age or older, and another 11% (24/221) were between the ages of 45 and 64 years old, in keeping with the age-groups usually affected by A/H3N2. (Note that numbers may fluctuate because of the delays in reporting).
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