March 15, 2009 to March 21, 2009 (Week 11)

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Overall influenza activity in Canada remains similar to previous weeks
During week 11, 3 regions (in BC) reported widespread activity, 16 regions localized (in AB, SK, ON, QC, NB & NF), 28 regions sporadic and 1 region reported no activity (see map). No report was received from NT and MB. The proportion of tests that were positive for influenza increased from the previous week (percentage positive = 17.9%; 824/4,592) (see table). To date this season, 59% (4,264/7,227) of detections are influenza A (see graph). This week, the ILI consultation rate rose to 28 ILI consultations per 1,000 patient visits (see ILI graph) which is within the expected range for this time of year. The sentinel response rate was 54%. In week 11, 30 new influenza outbreaks were reported: 10 in LTCFs (BC, ON, QC, & NB), 14 in schools (BC, SK & NB), 3 in hospitals (BC & AB) and 3 other outbreaks.

Antigenic Characterization:
Since 1 September 2008, the NML has antigenically characterized 694 influenza viruses: 154 influenza A/Brisbane/59/2007(H1N1)-like (from BC, AB, SK, ON, QC, NB, NS & PEI), 132 influenza A/Brisbane/10/2007(H3N2)-like (from BC, AB, SK, MB, ON, QC, NB, PEI & NL), 7 influenza B/Florida/4/2006-like (from AB, ON & QC), 40 B/Brisbane/60/2008-like and 361 B/Malaysia/2506/2004-like (in all provinces except the Territories). A/Brisbane/59/2007(H1N1), A/Brisbane/10/2007(H3N2) and B/Florida/04/2006 are the influenza A and influenza B components recommended for the 2008-09 influenza vaccine. B/Malaysia/2506/2004 was the influenza B component for the 2007-2008 season vaccine (see pie chart). B/Brisbane/60/2008-like is the recommended influenza B component for the 2009-2010 season vaccine.

Antiviral Resistance:

Results from the NML:

Since the start of the season, the NML has tested 387 influenza A isolates (184 H1N1 and 203 H3N2) for amantadine resistance. All of the H1N1 isolates were susceptible; however all of the H3N2 isolates were resistant to amantadine (resistance = 100%). The resistant isolates were from BC, AB, SK, MB, ON, QC, NB, PEI, NL & NT.

The NML has also tested 655 influenza isolates (158 A/H1N1, 109 A/H3N2 & 388 B) for oseltamivir (Tamiflu) resistance. All of the A/H3N2 and B isolates were sensitive; however all of the A/H1N1 isolates were resistant to oseltamivir due to the H274Y mutation (resistance = 100%). The resistant isolates were from BC, AB, SK, ON, QC, NB, NS, PEI & NL.

All 626 influenza isolates (130 A/H1N1, 107 A/H3N2 & 389 B) tested for zanamivir resistance to date were sensitive to zanamivir.

Oseltamivir resistance findings from Provincial laboratories:

To date this season, 128 influenza isolates in BC have been sub-typed as A/H1 and were assessed genotypically for oseltamivir resistance using an SNP assay. One hundred and seventeen isolates tested positive for the H274Y mutation (resistance = 100% or 117/117), with the other 11 specimens still pending confirmatory testing.

Influenza-associated Paediatric Hospitalizations:
In week 11, 47 laboratory-confirmed influenza-associated paediatric hospitalizations were reported through the Immunization Monitoring Program Active (IMPACT) network. To date, 414 hospitalizations have been reported of which 69% have been due to influenza A. The proportion of cases to date by age group are as follows: 23% were 0-5 month olds; 18% were 6-23 month olds; 12% were 2-4 year-olds; 12% were 5-9 year-olds; and 35% were 10-16 year-olds. The distribution of cases to date by province are as follows: 9% from BC, 6% from AB, 4% from SK, 2% from MB, 32% from ON, 43% from QC, 4% from NS & 0.5% from NL. For week 11, a second influenza-associated pediatric death due to influenza B was reported in Quebec. This child was between 2 to 4 years of age and previously healthy. This is the second influenza-associated pediatric death reported in Canada this season. One was due to influenza A, the other due to influenza B.

International:

CDC: During week 10, influenza activity decreased slightly in the United States; 1,102 (21.7%) specimens tested positive for influenza, of which 47% were influenza A and 53% were influenza B. Testing for antiviral resistance indicated that of the influenza virus A/H1N1 tested, 98.9% were resistant to oseltamivir and 0.6% resistant to amantadine. Of the influenza A/H3N2 viruses tested for resistance, 100% were resistant to amantadine. All tested viruses remain sensitive to zanamivir. To date this season, 32 influenza-associated pediatric deaths have been reported to the CDC (6 of which were reported in week 10). Bacterial co-infections were confirmed in 8 (40%) of 20 tested children; Staphylococcus aureus was identified in 5 (63%) of 8 tested children.

• CDC

EISS: Influenza activity remained high in the Russian Federation while continuing to decline or remain low in most western, central and northern European countries. Influenza A(H3) continues to be the predominant circulating virus overall this season, however, influenza B virus detections are currently dominant in over 50% of the countries. Of the 280 A(H3N2) isolates that were tested for adamantanes susceptibility, 280 (100%) were resistant. Of the 207 A(H1N1) virus isolates tested for resistance against neuraminidase inhibitors, 203 (98%) were resistant to oseltamivir, but all were sensitive to zanamivir.

• EISS

Human Avian Influenza: Since 21 March 2009, the WHO reported one new case of human H5N1 avian influenza infection in Egypt.

• WHO

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Total number of influenza tests performed and number of positive tests by province/territory of testing laboratory, Canada, 2008-2009

Province of reporting laboratories	Report Period: March 15, 2009 to March 21, 2009				Season to Date: August 24, 2008 to March 21, 2009
	Total # Influenza Tests	# of Positive Tests			Total # Influenza Tests	# of Positive Tests
		Influenza A	Influenza B	Total		Influenza A	Influenza B	Total
NL	43	8	1	9	659	75	9	84
PE	7	1	0	1	177	14	8	22
NS	26	9	6	15	790	39	42	81
NB	105	43	5	48	1153	198	69	267
QC	1840	201	115	316	26119	1922	1138	3060
ON	982	111	74	185	23612	726	1209	1935
MB	70	2	8	10	1707	22	22	44
SK	278	22	26	48	4072	109	101	210
AB	1085	78	37	115	17805	651	212	863
BC	156	62	15	77	2346	508	153	661
Canada	4592	537	287	824	78440	4264	2963	7227

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.

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)

Respiratory virus laboratory detections in Canada, by geographic regions, are available weekly on the following website:
<http://www.phac-aspc.gc.ca/bid-bmi/dsd-dsm/rvdi-divr/index-eng.php>

Number of influenza surveillance regions† reporting widespread or localized influenza activity, Canada, by report week, 2008-2009 (N=54)

† sub-regions within the province or territory as defined by the provincial/territorial epidemiologist. Graph may change as late returns come in.

Influenza Activity Level by Provincial and Territorial Influenza Surveillance Regions, Canada, March 15, 2009 to March 21, 2009
	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 outbreaks. Please refer to detailed definitions. For areas where no data is reported, late reports from these provinces and territories will appear on the FluWatch website. Select single maps by report week to get this updated information.
<http://dsol-smed.phac-aspc.gc.ca/dsol-smed/fluwatch/fluwatch.phtml?lang=e>

Click on the map to view provinces/territories and maps for other weeks.

Influenza tests reported and percentage of tests positive, Canada, by report week, 2008-2009

Percent positive influenza tests, compared to other respiratory viruses, Canada, by reporting week, 2008-2009

Influenza strain characterization, Canada, cumulative, 2008-2009 influenza season by the Respiratory Viruses Section at the National Microbiology Laboratory
[N=694]

{Strain characterization, number identified, per cent of total number}

NACI recommends that the trivalent vaccine for the 2008-2009 season in Canada contain
A/Brisbane/59/2007 (H1N1)-like virus; an A/Brisbane/10/2007 (H3N2)-like virus; and a B/Florida/4/2006-like virus.

Influenza-like illness (ILI) consultation rates, Canada, by report week,
2008-2009 compared to 1996/97 through to 2007/08 seasons

Note: No data available for mean rate in previous years for weeks 19 to 39 (1996-1997 through 2002-2003 seasons).

Number of New Outbreaks in Long Term Care Facilities, Canada, by Report Week, 2008-2009

 

Please note that the above graphs may change as late returns come in.

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Definitions for the 2008-2009 season