May 17, 2009 to May 23, 2009 (Week 20)

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Overall influenza activity continues to decline
During week 20 the reported activity level, consultations rates and number of new outbreaks decreased, while the proportion of tests positive for influenza increased slightly. Five regions in AB, SK, ON reported localized activity, 38 regions sporadic activity in BC, AB, SK, MB, ON, QC, NB, PE, NS, NL, & NU and 11 regions in ON, NB, NS, NL, NWT & YK reported no activity (see map). This week, the ILI consultation rate decreased to 14 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 58%. The proportion of tests that were positive for influenza was 5.2% which is slightly higher than the two previous weeks (see table). The majority (63.7%) of influenza virus detections this season have been for influenza A. One new influenza outbreaks was reported in a LTC facility in Ontario.

H1N1 Flu Virus (Human Swine Flu)
As of May 27, 2009 (15:00 EDT), a total of 1,118 laboratory-confirmed cases of the H1N1 Flu Virus (Human Swine Flu) were reported from nine provinces and one territory [(BC (120; 11%), AB (109; 9.7%), SK (104; 9.3%), MB (6; 0.5%), ON (495; 44%), QC (207; 19%), NB (2 ;0.2%), NS (71; 6.4%), PE (3; 0.3%), YK (1:0.01%)]. The mean age reported was 17 years (range <1 to 86 years). Forty-three laboratory confirmed cases have been hospitalized and two deaths reported. Globally there have been 13,398 cases and 95 deaths reported in 48 countries.

Antigenic Characterization:
Since 1 September 2008, the NML has antigenically characterized 953 influenza viruses: 239 influenza A/Brisbane/59/2007(H1N1)-like (from BC, AB, SK, MB, ON, QC, NB, NS & PEI), 163 influenza A/Brisbane/10/2007(H3N2)-like (from BC, AB, SK, MB, ON, QC, NB, PEI & NL), 11 influenza B/Florida/4/2006-like (from AB, ON, QC & NB), 167 B/Brisbane/60/2008-like (from BC, AB, SK, MB, ON, QC, NB, NL & NU) and 373 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.

As of May 29, 2009 the NML tested 209 specimens for influenza H1N1 Flu Virus (Human Swine Flu) and 121 were positive. Positive samples were from AB, SK, MB, ON, QC, NB, PEI, NS. *Provincial labs are also doing their own confirmation using RT-PCR.

Antiviral Resistance:

Results from the NML:

Since the start of the season, the NML has tested 562 influenza A isolates (257 H1N1 and 305 H3N2) for amantadine resistance. All of the H1N1 isolates were susceptible; 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 930 influenza isolates (253 A/H1N1, 166 A/H3N2 & 511 type B) for oseltamivir (Tamiflu) resistance. All of the A/H3N2 and B isolates were sensitive; 252 (99.6%) of the A/H1N1 isolates were resistant to oseltamivir due to the H274Y mutation. The resistant isolates were from BC, AB, SK, MB, ON, QC, NB, NS, PEI & NL. All 875 influenza isolates (202 A/H1N1, 162 A/H3N2 & 511 B) tested for zanamivir resistance to date were sensitive to zanamivir.

Forty H1N1 Flu Virus (Human Swine Flu) isolates have been tested for resistance to amantadine, 56 for oseltamivir and 8 for zanamivir. The testing results showed all were resistant to amantadine but suspectible to oseltamivir and zanamivir.

Influenza-associated Paediatric Hospitalizations:
In week 20, nine laboratory-confirmed influenza-associated paediatric hospitalizations were reported through the Immunization Monitoring Program Active (IMPACT) network four were type A (2 ON, 2 QC) and five were H1N1 Flu Virus (Human Swine Flu) (3 ON, 2 QC). Since its emergence a total of 11 hospitalizations have been associated with the Human Swine Flu. To date this season, 434 hospitalizations have been reported, this is similar to the number of hospitalizations seen at this same time during the past five years (range 334- 469); 56.9% of hospitalizations have been due to influenza A. The proportion of cases to date by age group are as follows: 14% were 0-5 month olds; 31% were 6-23 month olds; 23% were 2-4 year-olds; 16% were 5-9 year-olds; and 16% were10-16 year-olds. The distribution of cases to date by province are as follows: 10% from BC, 9% from AB, 4.5% from SK, 4.5% from MB, 28.5% from ON, 40% from QC, 3% from NS & 0.5% from NL.

International:

WHO: During weeks 19-20 influenza sesonal activity continued to increase in the souther hemispere with more countries reporting low levels of activity. New Zealand (H1, H3) and South Africa (H3, B) reported local levels of activity.

• WHO

CDC: During week 19 (May 10-May 16, 2009), influenza activity decreased in the U.S. but ILI levels were still higher than normal for this time of year. Of the 1074 specimens tested positive for influenza (72%) were positive were for novel influenza A H1N1. One-hundred and twenty eight samples of the novel influenza A (H1N1) were tested for antiviral resistance. None were resistant to Oseltamivir or Zanamivir. Of 96 samples tested for resistance to Adamantanes 100% were resistant. Two influenza -associated pediatric deaths were reported this week (one due to influenza A and one due to influenza B). These deaths occured between April 12 and April 25, 2009. Bacterial co-infections were observed in 13 (42%) of children and Staphylococcus aureus was identified in eight (62%) of children tested.

• CDC

EISS: In week 21 (May 18-May 24, 2009), influenza activity remained low but substantial infection with the novel influenza A H1N1 were reported in Europe. For the intensity indicator, the national network levels of influenza-like illness (ILI) and/or acute respiratory infection (ARI) were low in all countries that reported this indicator. For the geographical spread indicator, all countries reported sporadic or no activity. All novel influenza A (H1N1) viruses tested were sensitive to oseltamivir and zanamivir but resistant to M2 inhibitors.

• EISS

Human Avian Influenza: On May 28, 2009 the WHO reported two new cases of 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: May 17, 2009 to May 23, 2009				Season to Date: August 24, 2008 to May 23, 2009
	Total # Influenza Tests	# of Positive Tests			Total # Influenza Tests	# of Positive Tests
		Influenza A	Influenza B	Total		Influenza A	Influenza B	Total
NL	4	0	0	0	1182	128	25	153
PE	4	0	0	0	219	17	9	26
NS	75	2	0	2	2096	96	59	155
NB	46	0	1	1	2099	267	95	362
QC	1081	57	2	59	37561	2506	1408	3914
ON	1239	57	1	58	33066	1303	1342	2645
MB	189	14	0	14	2893	101	35	136
SK	331	85	4	89	6621	430	216	646
AB	1557	20	12	32	34606	1001	457	1458
BC	245	15	0	15	6799	900	207	1107
Canada	4771	250	20	270	127142	6749	3853	10602

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, May 17, 2009 to May 23, 2009 (Week 20)
	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=1047]

{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