May 3, 2009 to May 9, 2009 (Week 18)

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Slight Increase in Influenza Activity
For the second week in a row there was a small increase in reported activity level, consultation rates, and proportion of positive tests for influenza A. One region in BC reported widespread activity, eleven regions in BC, AB, MB, ON & NB reported localized activity, 31 regions sporadic in BC, AB, SK, MB, ON, QC, NB, PE, NS, NL, NWT, NU and 10 regions in MB, ON, NB, NS, YK, NWT & NU reported no activity (see map). This week, the ILI consultation rate increased to 19 consultations per 1,000 patient visits (see ILI graph) which is significantly above the expected range for this time of year. This is likely due to continued concerns over the Influenza H1N1 Flu Virus (Human Swine Flu). The sentinel response rate was 61%. The proportion of tests that were positive for influenza increased to 4.6% up from 4% in the previous week (see table). Twelve new influenza outbreaks were reported this week; three were in LTCFs (1 in AB and 2 in ON), one in a hospital in NB, six were in schools (4 in BC and 2 in AB), and two occured in unspecified locations in BC and ON.

As of May 14, 2009 (15:00 EDT), a total of 449 laboratory-confirmed cases of the H1N1 Flu Virus were reported from all but three jurisdictions in Canada (NL, NU, and NWT). Among cases with information available, (n=365), the median age was 21 years and 225 (61.6%) were between 10-29 years old. 35 (9.5%) of cases were <10 years of age and 1.4% were >=65 years old. Typically influenza illness is observed in the young (0-4 years) and older (>=65 years) age groups. Information on travel history was missing for 48 cases (13.2%) and of the remaining 317 cases, 153 (48.3%) reported a history of travel in the 7 days prior to symptom onset and 164 (51.7%) did not. Information on hospitalization was available for 155 cases of which 13 cases (8.4%) had been hospitalized [BC (3; 23%), AB (4; 31%), MB (1; 8%), ON (3; 23%), and QC (2; 15%)]. The median age of hospitalized cases was 28.5 years compared to 22 years among non-hospitalized cases and 21 years among all reported cases. Globally there have been 6,497 cases of Influeza A (H1N1) and 65 deaths reported in 33 countries.

Antigenic Characterization:
Since 1 September 2008, the NML has antigenically characterized 906 influenza viruses: 226 influenza A/Brisbane/59/2007(H1N1)-like (from BC, AB, SK, MB, ON, QC, NB, NS & PEI), 154 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), 147 B/Brisbane/60/2008-like (from BC, SK, MB, ON, QC, NB, NL & NU) 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. Additionally, as of May 14, 2009 of the 152 samples submitted to the NML 89 (59%) have confirmed Influenza H1N1 Flu Virus (Human Swine Flu). Positive samples were from PEI, NS, QC, ON, MB, SK, and AB. *Provincial labs have also been doing their own confirmation using RT-PCR and as of May 14, 2009, 138 samples were confirmed. Samples were from all provinces excluding NL. The age distribution of the samples was as follows; 7 (0-4 years), 48 (5-19 years), 79 (20-64 years), and 2 (65 years and older). Age is unknown for two of the samples.

Antiviral Resistance:

Results from the NML:

Since the start of the season, the NML has tested 558 influenza A isolates (254 H1N1 and 304 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 930 influenza isolates (252 A/H1N1, 166 A/H3N2 & 511 type 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 875 influenza isolates (202 A/H1N1, 162 A/H3N2 & 511 B) tested for zanamivir resistance to date were sensitive to zanamivir.

Oseltamivir resistance findings from Provincial laboratories:

To date this season, 163 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-eight isolates tested positive for the H274Y mutation (resistance = 100% or 148/148), with the other 15 specimens still pending confirmatory testing.

Influenza-associated Paediatric Hospitalizations:
In week 18, two laboratory-confirmed influenza-associated paediatric hospitalizations were reported through the Immunization Monitoring Program Active (IMPACT) network one from MB (type A) and one H1N1 Human Swine flu in QC. To date this season, 418 hospitalizations have been reported, this is similar to the number of hospitalizations seen at this same time during the past five years (range 330- 452). 55%of hospitalizations have been due to influenza A. The proportion of cases to date by age group are as follows: 14.5% were 0-5 month olds; 31% were 6-23 month olds; 23.5% were 2-4 year-olds; 15.5% were 5-9 year-olds; and 15.5% were10-16 year-olds. The distribution of cases to date by province are as follows: 10% from BC, 9% from AB, 5% from SK, 5% from MB, 28% from ON, 40% from QC, 3% from NS & 0.5% from NL.

International:

EISS: In week 19 (May 04-May 10, 2009), influenza activity remained at baseline levels, with sentinel virus detections being low, in almost all of Europe. For the intensity indicator, the national network levels of influenza-like illness (ILI) and/or acute respiratory infection (ARI) were low in almost all countries that reported this indicator. Only Albania and two of seven regions (Siberian and Urals) of the Russian Federation reported medium intensity. For the geographical spread indicator, the Russian Federation reported local activity whereas all other countries reported sporadic or no activity. Influenza A(H3N2) has been the dominant virus in Europe this season, accounting for an estimated 69% of total virus detections this season. Of the 644 A(H3N2) isolates that were tested for adamantanes susceptibility, 644 (100%) were resistant. Of the 259 A(H1N1) virus isolates tested for resistance against neuraminidase inhibitors, 255 (98%) were resistant to oseltamivir, but all were sensitive to zanamivir.

• EISS

Human Avian Influenza: During week 18, the WHO reported two new cases of human H5N1 avian influenza infection; one in Egypt, one in Viet Nam.

• 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 3, 2009 to May 9, 2009				Season to Date: August 24, 2008 to May 9, 2009
	Total # Influenza Tests	# of Positive Tests			Total # Influenza Tests	# of Positive Tests
		Influenza A	Influenza B	Total		Influenza A	Influenza B	Total
NL	135	14	1	15	1123	123	25	148
PE	10	3	0	3	199	17	9	26
NS	NA	NA	NA	0	1321	70	59	129
NB	285	10	1	11	1932	265	92	357
QC	1269	35	11	46	35404	2398	1404	3802
ON	629	25	0	25	30183	1177	1328	2505
MB	210	14	2	16	2543	77	35	112
SK	393	17	6	23	5912	264	203	467
AB	3865	63	46	109	30389	943	418	1361
BC	1237	117	5	122	4967	833	199	1032
Canada	8033	298	72	370	113973	6167	3772	9939

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 3, 2009 to May 9, 2009 (Week 18)
	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=995]

{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