Overall influenza activity in Canada remains low
During week 51, influenza activity in Canada remained low overall with the majority of the influenza surveillance regions still reporting no activity. Eleven regions (in BC, AB & QC) reported sporadic influenza activity (see map). Note that no data for Newfoundland and Labrador and Ontario were received this week. Thirty-two specimens tested positive for influenza in Canada this week (percentage positive = 1.3%; 32/2,383) (see table). The majority of influenza virus detections to date this season were influenza A viruses (61% or 99/162). In week 51, the ILI consultation rate increased slightly to 19 ILI consultations per 1,000 patient visits (see ILI graph), and is within the expected range for this week. The sentinel response rate was 62%. No new influenza outbreaks were reported in week 51.

Respiratory Syncytial Virus (RSV): RSV detections for Canada as a whole have been increasing steadily since mid-November (see graph). The majority of RSV detections to date were from QC, ON and AB. Similar to influenza, RSV demonstrates winter seasonality with activity usually starting in the late fall, peaking in the winter and tapering off in the late spring.

Antigenic Characterization:
Since 1 September 2008, the NML has antigenically characterized 20 influenza viruses: 3 influenza A/Brisbane/59/2007(H1N1)-like (from ON & NS), 2 influenza A/Brisbane/10/2007(H3N2)-like (from BC & ON), 3 influenza B/Florida/4/2006-like (from ON and AB) and 12 B/Malaysia/2506/2004-like (from ON and AB). A/Brisbane/59/2007(H1N1), A/Brisbane/10/2007(H3N2) and B/Florida/4/2006 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).

Antiviral Resistance:
Results from the NML:
Since the start of the season, the NML has tested 11 influenza A isolates (6 H1N1 and 5 H3N2) for amantadine resistance. All of the H1N1 isolates were susceptible; however all of the H3N2 isolates were resistant to amantadine (resistance = 100% or 5/5). The resistant isolates were from ON, AB and BC.

The NML has also tested 22 influenza isolates (5 A/H1N1, 2 A/H3N2 & 15 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% or 5/5). The resistant isolates were from NS, ON and BC.

All 18 influenza isolates (1 A/H1N1, 2 A/H3N2 & 15 B) tested for zanamivir resistance to date were sensitive to zanamivir.

Oseltamivir resistance findings from Provincial laboratories:
To date this season, 19 influenza isolates in BC have been sub-typed as A/H1 and were assessed genotypically for oseltamivir resistance using an SNP assay. Fourteen isolates tested positive for the H274Y mutation (resistance = 100% or 14/14), with the other 5 specimens still pending confirmatory testing. These specimens were from community-based cases of ILI; none were associated with an outbreak.

Influenza-associated Paediatric Hospitalizations:
No laboratory-confirmed influenza-associated paediatric hospitalizations have been reported through the Immunization Monitoring Program Active (IMPACT) network for the 2008-09 season.

International:

EISS: In week 51, influenza activity reached high intensity in Portugal and medium intensity in Bulgaria, Ireland, Spain and the United Kingdom. Most of the influenza virus detections so far have been for influenza A viruses of which the majority were A(H3). Of the 40 A(H3N2) isolates that were also tested for adamantanes susceptibility, all were resistant. Of the 29 A(H1N1) virus isolates tested for resistance against neuraminidase inhibitors, 28 were resistant to oseltamivir (resistance=97%), but all were sensitive to zanamivir.

• EISS

Human Avian Influenza: No new cases of human H5N1 avian influenza infection have been reported by the WHO since 16 December 2008.

• 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: December 14, 2008 to December 20, 2008				Season to Date: August 24, 2008 to December 20, 2008
	Total # Influenza Tests	# of Positive Tests			Total # Influenza Tests	# of Positive Tests
		Influenza A	Influenza B	Total		Influenza A	Influenza B	Total
NL	25	0	0	0	149	0	0	0
PE	22	0	0	0	60	0	0	0
NS	30	0	0	0	240	1	0	1
NB	17	0	0	0	165	0	0	0
QC	642	3	0	3	5719	37	2	39
ON	848	5	6	11	7353	11	13	24
MB	32	0	0	0	743	0	0	0
SK	102	0	0	0	1220	0	0	0
AB	595	6	6	12	6910	15	47	62
BC	70	6	0	6	613	35	1	36
Canada	2383	20	12	32	23172	99	63	162

 

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, December 14, 2008 to December 20, 2008 (Week 51)
	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=20]

{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