June 7, 2009 to June 13, 2009 (Week 23)

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Pandemic H1N1 2009 virus Surveillance and Epidemiology

As of 17 June, 2009, all provinces and territories have reported a total of 4,905 laboratory-confirmed cases of H1N1 flu virus, of which 298 H1N1 cases were admitted to hospital. Cases were distributed similarly between males and females (48.6% for males, 50.9% for females, 0.5% unknown). These cases were from British Columbia (2.0%), Alberta (3.4%), Saskatchewan (2.0%), Manitoba (14.4%), Ontario (18.1%), Quebec (53.7%), Nova Scotia (0.3%) and Nunavut (6.1%). Of the 298 hospitalized cases, core data are available for 262 (87.9%) cases. The median age of the hospitalized cases was 18 years (range <1 to 85 years). Forty-nine (18.7%) of the hospitalized cases were reported to have been admitted to the intensive care unit (ICU). Information regarding underlying medical conditions was available for 85 hospitalized cases. Among theses, 30 cases (35%) have underlying medical conditions, including lung disease (8), diabetes (3), kidney disease (2), immune suppression (4) and chronic heart disease (5), and other underlyings conditions (16) (note that some cases reported more than one underlying condition). Two hospitalized cases were pregnant women, both in their 3rd trimester. There have been also 12 deaths reported since the beginning of the outbreak among the following age groups : 10 to 19 years (8.3%), 30 to 39 years (16.7%), 40 to 49 years (33.3%), 50 to 59 years (25.0%) and ≥ 60 years (16.7%). Eleven had underlying medical conditions and one was over age 65.

Weekly and cumulative numbers of hospitalizations and deaths due to H1N1 flu virus, Canada,
to 17 June 2009

Province/Territory	This week  (11-17 June, 2009) hospitalized cases	This week  (11-17 June, 2009) deaths	Cumulative hospitalized  cases	Cumulative deaths
BC	1	0	6	0
AB	4	0	10	1
SK	4	0	6	0
MB	31	2	43	2
ON	16	0	54	2
QC	89	6	160	7
NB	0	0	0	0
NS	0	0	1	0
PE	0	0	0	0
NL	0	0	0	0
YT	0	0	0	0
NT	0	0	0	0
NU	8	0	18	0
Canada	153	8	298	12

Overall Influenza Summary

During week 23, the reported activity level (one region reported widespread activity), ILI consultations rates (41 consultations per 1,000 visits) and proportion of influenza positive tests (26.1%) are still higher than expected for this time of the year.

One region in AB reported widespread activity, nine regions in AB, SK, ON & NU reported localized activity, 26 regions sporadic activity in BC, SK, ON, QC, NB, NS, NL, NT & NU and 14 regions in NB, NS, PE, NL, YK & NT reported no activity (no report received from MB and from 1 region in NL). Eleven new influenza outbreaks were reported this week; one was in a LTCF (AB), seven were in schools (AB) and two occured in unspecified locations (AB & NU).

Map of overall Influenza activity level
by provinces and territories, Week 23 Canada

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 reported outbreaks. Please refer to detailed definitions on the last page. For areas where no data is reported, late reports from these provinces and territories will appear on the FluWatch website.

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.

Number of New Outbreaks in Long Term Care Facilities, Canada, by Report Week, 2008-2009

ILI consultation rate

This week, the ILI consultation rate increased to 41 consultations per 1,000 patient visits (see ILI graph) which is comparable to the level observed during the seasonal influenza peak (week 9). The sentinel response rate was 77.8%.

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).

Paediatric Influenza Hospitalizations and deaths

In week 23, eighty-one laboratory-confirmed influenza-associated paediatric hospitalizations were reported through the Immunization Monitoring Program Active (IMPACT) network from BC, AB, SK, ON & QC. Thirty-eight (46.9%) cases were due to H1N1 flu virus this week (66% were between age 5 to 16). To date this season, 671 hospitalizations have been reported; 54.8% of hospitalizations have been due to influenza A. The proportion of cases to date by age group are as follows: 11.5% were 0-5 month olds; 26% were 6-23 month olds; 22% were 2-4 year olds; 19% were 5-9 year olds; and 21.5% were 10-16 year olds. The distribution of cases to date by province are as follows: 7% from BC, 7.5% from AB, 3% from SK, 10% from MB, 29% from ON, 41% from QC, 2% from NS & 0.5% from NL.

Laboratory Surveillance Summary
This week, the proportion of tests that were positive for influenza was 26.1% which is considerably higher than the previous weeks (see table). The majority (74.4%) of influenza virus detections this season have been for influenza A. 99.95% of influenza virus detections this week have been for influenza A likely due to the H1N1 flu virus.

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: June 07, 2009 to June 13, 2009				Season to Date: August 24, 2008 to June 13, 2009
	Total # Influenza Tests	# of Positive Tests			Total # Influenza Tests	# of Positive Tests
		Influenza A	Influenza B	Total		Influenza A	Influenza B	Total
NL	21	0	0	0	1258	128	26	154
PE	6	0	0	0	239	17	9	26
NS	57	4	0	4	2256	108	60	168
NB	38	1	0	1	2273	268	95	363
QC	1870	344	0	344	41532	3065	1413	4478
ON	3424	1064	0	1064	42945	4178	1346	5524
MB	691	171	0	171	4097	393	37	430
SK	539	146	1	147	7774	705	219	924
AB	1296	348	0	348	37714	1459	462	1921
BC	144	35	0	35	7302	966	208	1174
Canada	8086	2113	1	2114	147390	11287	3875	15162

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.

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 Tests Received from Provincial Labs with subtyping capacity, Canada, 2008-2009

Reporting provinces	Influenza A					Influenza B
	Total	A(H1)	A(H3)	A(H1N1 flu virus)	A(not subtyped)
BC	966	7	6	55	898	208
AB	1459	0	4	59	1396	462
SK	705	21	78	284	322	219
MB	393	7	35	130	221	37
ON	4178	135	123	1498	2422	1346
QC	3065	0	0	0	3065	1413
NB	268	3	3	0	262	95
NS	108	23	22	7	56	60
PE	17	3	0	0	14	9
NL	128	2	3	0	123	26
Canada	11287	201	274	2033	8779	3875

Antigenic Characterization
Since 1 September 2008, the NML has antigenically characterized 973 influenza viruses: 241 influenza A/Brisbane/59/2007(H1N1)-like (from BC, AB, SK, MB, ON, QC, NB, NS & PEI), 166 influenza A/Brisbane/10/2007(H3N2)-like (from BC, AB, SK, MB, ON, QC, NB, NS, PEI & NL), 11 influenza B/Florida/4/2006-like (from AB, ON, QC & NB), 176 B/Brisbane/60/2008-like (from BC, AB, SK, MB, ON, QC, NB, NL & NU) and 379 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. All influenza A isolates are a good match to this season’s influenza vaccine while only 11/566 (1.9%) of influenza B viruses match this season’s vaccine. As of 18 June, 2009 the NML tested 510 specimens for influenza H1N1 Flu Virus and 276 were positive. Positive samples were from AB, SK, MB, ON, QC, NB, NS and PEI.
*Provincial labs are also doing their own confirmation using RT-PCR.

Antiviral Resistance (from NML)
Oseltamivir: 290/291 A/H1N1 isolates were resistant (99.7%). Zanamivir: All A/H1N1 isolates tested were sensitive (0%). Adamantanes: 305/305 A/H3N2 isolates were resistant to amantadine (100%). All Pandemic H1N1 2009 viruses tested so far have been sensitive to oseltamivir (100 samples) and zanamivir (52 samples) but resistant to amantadine (201 samples).

International update:

WHO: During weeks 21-22 activity continued to increased in some countries in the southern hemisphere. South Africa reported regional outbreaks due to H3 with low levels of B circulating. Local outbreaks occured in New Zealand (H1, H3) and Peru (H1), and Brazil reported increased activity of H3. Sporadic acitivity was observed in Argentina (A), China (H1, H3, B), Ecuador (H1, H3, B), Estonia (B), Iran (B), Italy (H1, B), Japan (H3, B), Madagascar (H3, B).

• WHO

Australia: As of May 22, 2009 influenza notifications are higher relative to the 5-year average for this time in their season (4.9 vs. 2.3 per 100,000) likely due to increased testing for the H1N1 flu virus. There have been over 2100 cases of H1N1 flu virus with no deaths reported to date.

• www.health.gov.au

Other Reports: In Chile during week 21, 90% of the circulating virus was due to the H1N1 flu virus. As of June 18, 2009 there have been 3,125 cases infected with the pandemic virus or which 77% have recovered and four deaths. The majority (66%) of cases have been between 5-19 years with 2% considered severe requiring hospitalizations.

Northern Hemisphere
CDC: During week 22 (May 31-June 6, 2009), influenza activity decreased in the United States, however, there are still higher levels of influenza-like illness than is normal for this time of year. 2,071 specimens tested positive for influenza A (77.8%) were positive for H1N1 flu virus. One-hundred and eighty-four samples of H1N1 flu virus were tested for antiviral resistance. None were resistant to oseltamivir or zanamivir. Of 141 samples tested for resistance to adamantanes, 100% were resistant. Three influenza -associated pediatric deaths were reported during week 22 due to influenza A; two with H1N1 flu virus and one with seasonal influenza A (H1N1). The deaths reported this week occurred between February 15, 2009 and May 30, 2009. Bacterial co-infections were observed in 14 (41.2%) of children and Staphylococcus aureus was identified in nine (64.3%) of 14 children tested.

• CDC

EISS: In week 24 (June 8-14, 2009), Pandemic H1N1 2009 virus detections in the European region continue but influenza activity in the community remains at baseline levels. As of 19 June, 3,308 laboratory-confirmed cases of H1N1 flu virus have been reported in the European region. Virus detections outside the winter season are usually highly sporadic in Europe, so these detections are unusual for this time of the year. All H1N1 flu viruses tested have been sensitive to oseltamivir and zanamivir but resistant to M2 inhibitors.

• EISS

Human Avian Influenza: During week 23, the WHO reported no new case of H5N1 avian influenza infection.

• WHO

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FluWatch reports include data and information from five main sources: laboratory reports of positive influenza tests in Canada; sentinel physician reporting of influenza-like illness (ILI); provincial/territorial assessment of influenza activity based on various indicators, including laboratory surveillance, ILI reporting, school and work site absenteeism, and outbreaks; influenza-associated pediatric hospitalizations; WHO and other international reports of influenza activity.
The map shows influenza activity in the “influenza surveillance regions” † within each jurisdiction, as determined by the provincial/territorial epidemiologists.

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).

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Definitions for the 2008-2009 season