Influenza activity in Canada remains low overall; although some influenza indicators have slightly increased from the previous week
During week 03, influenza activity levels in Canada still remained fairly low overall; however, some influenza indicators (laboratory detections, ILI consultations and activity levels) increased slightly from the previous week. In week 03, 1 region in BC reported widespread activity, 6 influenza surveillance regions (in BC, AB, SK, MB & ON) reported localized influenza activity, and the rest reported either no activity (n=23) or sporadic activity (n=25) (see map). Note: No data was received from the Yukon this week. In week 03, the number of specimens that tested positive for influenza was 8.2% (297/3640). Of the influenza detections to date, 79% were influenza A and 21% were influenza B (see table). Influenza A detections predominated in most provinces except in AB and a few Atlantic provinces. This week, the ILI consultation rate increased to 26 ILI consultations per 1,000 patient visits (see ILI graph), which is within the expected range for this week. The sentinel response rate was low at 58%. Eight new outbreaks of influenza or ILI were reported this week as follows: 3 LTCFs, 4 schools and 1 other.
Respiratory Syncytial Virus (RSV): RSV detections for Canada as a whole have been increasing steadily since mid-November and have declined slightly in recent weeks (see graph). The majority of RSV detections to date were from QC and ON. 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:
The National Microbiology Laboratory (NML) has characterized 205 influenza viruses for the 2007-2008 influenza season: 140 A(H1N1), 14 A(H3N2) and 51 B viruses. All influenza A(H1N1) viruses were antigenically similar to A/Solomon Islands/3/2006. Of the 14 influenza A(H3N2) viruses characterized, 5 were antigenically similar to A/Wisconsin/67/2005 and 9 were antigenically similar to A/Brisbane/10/2007. One of the 5 A/Wisconsin-like viruses had reduced titer to A/Wisconsin/67/2005 reference antiserum. Of the 51 influenza B isolates characterized, 3 were antigenically similar to B/Malaysia/2506/2004 and 48 were antigenically similar to B/Florida/4/2006 (belonging to the B/Yamagata lineage) (see pie chart).

Antiviral Resistance:
Since the start of the season, the NML has tested 151 influenza A isolates (130 H1N1 and 21 H3N2) for amantadine resistance and found that 19 (90%) of the 21 H3N2 isolates were resistant to amantadine and 4 (3%) of 130 H1N1 isolates was resistant (see recommendation from the 2006-2007 influenza season below).
NML also tested 117 influenza isolates (74 A/H1N1, 11 A/H3N2 & 32 B) for oseltamivir (Tamiflu) resistance and found that 1 (1.4%) of the 74 H1N1 isolates tested was resistant to oseltamivir. Viruses that are resistant to neuraminidase inhibitor drugs have been detected in the past in untreated individuals.

Influenza-associated Paediatric Hospitalizations:
No new laboratory-confirmed influenza-associated paediatric hospitalizations were reported through the Immunization Monitoring Program Active (IMPACT) network this week. To date, 21 hospitalizations have reported so far (all from Ontario) and all have been due to influenza A. The proportion of cases to date by age group are as follows: 24% each among 6-23 month olds, 2-4 year-olds, and 5-9 year-olds; 14% each among 0-5 month olds and 10-16 year-olds.

International:

CDC: During week 02, influenza activity continued to increase in the United States. State reporting of activity levels were as follows: 4 widespread, 11 regional, 15 local, 19 sporadic and 1 no activity. The proportion of specimens that tested positive for influenza virus increased to 9.8% this week. The majority of influenza detections to date were for influenza A viruses (86%). Since September 30, 2007, CDC antigenically characterized 163 influenza viruses: 67 influenza A(H1) (all A/Solomon Islands/3/2006), 53 influenza A(H3) (6 A/Wisconsin/67/2005-like and 46 A/Brisbane/10/2007-like, and 1 showed somewhat reduced titers with antisera produced against A/Wisconsin and A/Brisbane), and 43 influenza B viruses (3 belonging to the B/Victoria and 40 B/Yamagata lineage). To date this season, 1 influenza-associated pediatric death has been reported to the CDC (in week 48).

• CDC

EISS: In week 3, medium or high influenza activity was reported in 16 of the 27 European countries, indicating that influenza is now affecting southern and eastern European regions. A further increase in consultations for ILI and/or ARI were reported. Of the total virus detections to date, 81% were influenza A and 99% were of the H1 subtype. The dominant virus strain circulating in Europe this season is A/Solomon Island/3/2006 which is included in the 2007-2008 vaccine.

• EISS

Human Avian Influenza: Since 19 January 2008, the WHO reported 3 additional cases of H5N1 avian influenza infection: 2 from Indonesia and 1 from Viet Nam. All 3 cases were fatal.

• WHO

Recommendation for the Use of Amantadine for Treatment and Prevention of Influenza
The Public Health Agency of Canada does not recommend the use of amantadine for treatment or prevention of influenza for the 2006-2007 season. This recommendation will be revisited if new information becomes available.

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Total number of influenza tests performed and number of positive tests by province/territory of testing laboratory, Canada, 2007-2008

Province of reporting laboratories	Report Period: January 13 to January 19, 2008				Season to Date: August 26, 2007 to January 19, 2008
	Total # Influenza Tests	# of Positive Tests			Total # Influenza Tests	# of Positive Tests
		Influenza A	Influenza B	Total		Influenza A	Influenza B	Total
NL	3	0	0	0	187	13	0	13
PE	7	0	0	0	38	0	0	0
NS	16	1	0	1	230	1	1	2
NB	19	1	0	1	271	1	1	2
QC	929	36	7	43	7457	113	17	130
ON	1195	103	5	108	10908	580	20	600
MB	66	2	0	2	1424	2	1	3
SK	180	12	6	18	2284	45	24	69
AB	1051	60	29	89	12885	136	170	306
BC	174	21	14	35	1122	120	31	151
Canada	3640	236	61	297	36806	1011	265	1276

 

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, 2007-2008 (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, 13 January to 19 January, 2008 (Week 3)
	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, 2007-2008

Percent positive influenza tests, compared to other respiratory viruses, Canada, by reporting week, 2007-2008

Influenza strain characterization, Canada, cumulative, 2007-2008 influenza season by the Respiratory Viruses Section at the National Microbiology Laboratory
[N=205]

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

NACI recommends that the trivalent vaccine for the 2007-2008 season in Canada contain A/Solomon Islands/3/2006 (H1N1)-like virus; an A/Wisconsin/67/2005 (H3N2)-like virus; and a B/Malaysia/2506/2004-like virus.

Influenza-like illness (ILI) consultation rates, Canada, by report week, 2007-2008 compared to 1996/97 through to 2006/07 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, 2007-2008

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

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Definitions for the 2007-2008 season