April 5, 2009 to April 11, 2009 (Week 14)

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Overall influenza activity in Canada is relatively similar to previous week
During week 14, overall influenza activity in Canada appears similar from previous week with some indicators having increased slightly (ILI consultation rate and outbreaks), but laboratory detections decreased and influenza activity level by province remained similar. This week, one region reported widespread activity, 15 regions localized (in BC, AB, MB, ON, QC, NB, & NL), 31 regions sporadic and 4 regions reported no activity (see map). (NT did not report) The proportion of tests that were positive for influenza decreased from the previous week (percentage positive = 10.7%; 352/3,296) (see table). To date this season, 60% (5,283/8,767) of detections are influenza A (see graph). This week, the ILI consultation rate was 24 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 14, 15 new influenza outbreaks were reported: 10 in LTCFs (BC, AB, MB & QC), 1 in a school (NS), 3 other outbreaks (AB) and 1 in a hospital (NL).

Antigenic Characterization:
Since 1 September 2008, the NML has antigenically characterized 828 influenza viruses: 202 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), 9 influenza B/Florida/4/2006-like (from AB, ON, QC & NB), 107 B/Brisbane/60/2008-like (from BC, SK, MB, ON, QC, NB & 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 527 influenza A isolates (242 H1N1 and 285 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 839 influenza isolates (225 A/H1N1, 154 A/H3N2 & 460 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 794 influenza isolates (176 A/H1N1, 152 A/H3N2 & 466 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 14, 2 laboratory-confirmed influenza-associated paediatric hospitalizations were reported through the Immunization Monitoring Program Active (IMPACT) network. The two cases were from AB and 50% were due to influenza A. To date, 383 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: 14% were 0-5 month olds; 30% were 6-23 month olds; 25% were 2-4 year-olds; 16% were 5-9 year-olds; and 15% were 10-16 year-olds. The distribution of cases to date by province are as follows: 9.5% from BC, 9% from AB, 4% from SK, 4% from MB, 30% from ON, 40% from QC, 3% from NS & 0.5% from NL.

*Note that the section on "Influenza-associated Paediatric Hospitalizations" of all the FluWatch reports from week 44, 2008 to week 11, 2009 have been revised due to technical errors identifies on week 12, 2009.

International:

WHO: No changes from previous report.

CDC: No changes from previous report.

EISS: Influenza activity in Europe is coming to an end for the 2008-2009 season. In week 15, all countries and regions in Europe, including all of the EU/EEA, reported decreasing influenza activity or baseline activity. One of the seven regions of the Russian Federation reported high influenza activity in week 15, but has passed its peak two weeks ago. Influenza A(H3N2) has been the dominant virus in Europe, accounting for an estimated 76% of total virus detections this season. Of influenza B viruses that have been antigenically and/or genetically characterized, 96% (871/908) were B/Victoria lineage. With the exception of these B/Victoria lineage viruses, most of the viruses characterized are similar to the three components - A(H1N1), A(H3N2) and B/Yamagata lineage - included in the 2008/2009 Northern Hemisphere influenza vaccine. Of the 415 A(H3N2) isolates that were tested for adamantanes susceptibility, 414 (99.8%) were resistant. Of the 227 A(H1N1) virus isolates tested for resistance against neuraminidase inhibitors, 223 (98%) were resistant to oseltamivir, but all were sensitive to zanamivir.

• EISS

Human Avian Influenza: During week 14, the WHO reported three new cases of human H5N1 avian influenza infection in Egypt and one new case in Vietnam.

• 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: April 5, 2009 to April 11, 2009				Season to Date: August 24, 2008 to April 11, 2009
	Total # Influenza Tests	# of Positive Tests			Total # Influenza Tests	# of Positive Tests
		Influenza A	Influenza B	Total		Influenza A	Influenza B	Total
NL	57	11	5	16	834	102	19	121
PE	1	0	0	0	183	14	8	22
NS	19	1	4	5	865	55	55	110
NB	53	6	3	9	1423	239	81	320
QC	1225	68	44	112	30460	2240	1331	3571
ON	796	64	16	80	26967	1032	1312	2344
MB	67	2	2	4	1970	39	28	67
SK	178	11	11	22	4751	168	160	328
AB	801	33	36	69	20498	793	309	1102
BC	99	27	8	35	2724	601	181	782
Canada	3296	223	129	352	90675	5283	3484	8767

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, April 4, 2009 to April 11, 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=828]

{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