March 29, 2009 to April 4, 2009 (Week 13)

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Overall influenza activity in Canada continues to decline
During week 13, no region reported widespread activity, 17 regions localized (in BC, AB, SK, ON, QC, NB, NL & NT), 34 regions sporadic and 2 regions reported no activity (see map). The proportion of tests that were positive for influenza decreased from the previous week (percentage positive = 12.3%; 507/4,132) (see table). To date this season, 60% (5,058/8,413) of detections are influenza A (see graph). This week, the ILI consultation rate was 20 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 53%. In week 13, 10 new influenza outbreaks were reported: 6 in LTCFs (BC, SK, ON, QC, NS & NT), 3 in schools (NB & BC) and 1 in hospitals (NS).

Antigenic Characterization:
Since 1 September 2008, the NML has antigenically characterized 812 influenza viruses: 198 influenza A/Brisbane/59/2007(H1N1)-like (from BC, AB, SK, MB, ON, QC, NB, NS & PEI), 142 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), 97 B/Brisbane/60/2008-like (from BC, SK, MB, ON, QC & NL) and 368 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 484 influenza A isolates (222 H1N1 and 262 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 813 influenza isolates (217 A/H1N1, 149 A/H3N2 & 447 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, MB, ON, QC, NB, NS, PEI & NL.

All 768 influenza isolates (173 A/H1N1, 148 A/H3N2 & 447 B) tested for zanamivir resistance to date were sensitive to zanamivir.

Oseltamivir resistance findings from Provincial laboratories:

To date this season, 156 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 forty-four isolates tested positive for the H274Y mutation (resistance = 100% or 144/144), with the other 12 specimens still pending confirmatory testing.

Influenza-associated Paediatric Hospitalizations:
In week 13, 19 laboratory-confirmed influenza-associated paediatric hospitalizations were reported through the Immunization Monitoring Program Active (IMPACT) network. The cases were from BC, AB, SK, ON, QC & NS and 53% were due to influenza A. To date, 376 hospitalizations have been reported of which 55% have been due to influenza A. The proportion of cases to date by age group are as follows: 16% were 0-5 month olds; 31% were 6-23 month olds; 25% were 2-4 year-olds; 16% were 5-9 year-olds; and 14% were 10-16 year-olds. The distribution of cases to date by province are as follows: 10% from BC, 9% from AB, 4% from SK, 4% from MB, 29.5% from ON, 40% from QC, 3% from NS & 0.5% from NL.

International:

CDC: During week 13, influenza activity continued to decrease in the United States; 348 (12.3%) specimens tested positive for influenza, of which 42% were influenza A and 58% were influenza B. Testing for antiviral resistance indicated that of the influenza virus A/H1N1 tested, 99.3% were resistant to oseltamivir and 0.4% 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, 45 influenza-associated pediatric deaths have been reported to the CDC (3 of which were reported in week 13). Bacterial co-infections were confirmed in 12 (44%) of 27 tested children; Staphylococcus aureus was identified in 8 (67%) of 12 tested children.

• CDC

EISS: Influenza activity in Europe is coming to an end for the 2008-2009 season: only two regions of the Russian Federation report high influenza activity while activity has returned to out of season levels. Influenza A(H3N2) has been the dominant virus in Europe, accounting for an estimated 77% of total viruses typed/subtyped this season. Detections of influenza A virus peaked in week 04/2009 and influenza B virus detections peaked around week 11/2009. Of influenza B viruses that have been antigenically and/or genetically characterised, 96% (765/798) were B/Victoria lineage. Of the 415 A(H3N2) isolates that were tested for adamantanes susceptibility, 414 (99.8%) were resistant. Of the 218 A(H1N1) virus isolates tested for resistance against neuraminidase inhibitors, 214 (98%) were resistant to oseltamivir, but all were sensitive to zanamivir.

• EISS

Human Avian Influenza: During week 13, 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 29, 2009 to April 4, 2009				Season to Date: August 24, 2008 to April 4, 2009
	Total # Influenza Tests	# of Positive Tests			Total # Influenza Tests	# of Positive Tests
		Influenza A	Influenza B	Total		Influenza A	Influenza B	Total
NL	67	10	1	11	777	91	14	105
PE	3	0	0	0	182	14	8	22
NS	24	9	7	16	846	54	51	105
NB	74	12	4	16	1370	233	78	311
QC	1556	112	63	175	29235	2172	1287	3459
ON	954	100	35	135	26118	966	1296	2262
MB	84	5	0	5	1903	37	26	63
SK	240	26	16	42	4573	157	149	306
AB	996	45	35	80	19697	760	273	1033
BC	134	17	10	27	2625	574	173	747
Canada	4132	336	171	507	87326	5058	3355	8413

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 29, 2009 to April 4, 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=812]

{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