July 12, 2009 to July 18, 2009 (Week 28)

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Pandemic (H1N1) 2009 virus Surveillance and Epidemiology

As of 18 July, 2009, all provinces and territories have reported a total of 10,449 laboratory-confirmed cases of Pandemic (H1N1) 2009 virus, of which 1,141 H1N1 cases were admitted to hospital. Core data was available for 1,116 (94.3%) hospitalizations. The median age of hospitalized cases was 21 years (range: <1 to 97 years) and 51.8% of cases hospitalized were female. Information on underlying medical conditions was available from 749 cases of which 60.4% had one or more underlying medical conditions: lung disease including asthma (191), diabetes (83), immune suppression (70), chronic heart disease (66) and kidney disease (34). Forty-five pregnant women have been hospitalized. Information on pregnancy trimester was available for 24 hospitalized women: 19 (79.2%) of them were in their third trimester. 184 (16.5%) hospitalized cases were reported to have been admitted to intensive care unit (ICU). The median age for cases in ICU was 38 years (range <1 to 82 years). The gender distribution was slightly higher for females admitted to ICU (59.2% female). Information on underlying medical conditions was completed for 154 ICU patients of which 107 (69.5%) had one or more underlying condition.

As of July 18, 2009, core data was available for 44 (89.8%) of 49 confirmed Pandemic (H1N1) 2009 deaths. The median age among death cases was 52 years (range: <1 to 83 years) and 61.4% were females. Information on the presence of an underlying medical condition was available for 33 of the death cases. Twenty-nine (87.9%) reported having at least one underlying medical conditions. Cases reporting underlying medical conditions were as follows: lung disease (10), chronic heart disease (6), diabetes (5) and immune suppressed (4). Two pregnant cases resulted in death. Information on pregnancy trimester was available for only 1 woman: she was in her third trimester.

The national abbreviated line list data was available for 6,672/10,449 (63.9%) cases. Among those, there were 634 cases who were Aboriginal. They were from Manitoba (174 cases), British Columbia (14 cases), and Quebec (27 cases). Also included in this group are 419 cases from Nunavut, an area with a predominant Inuit population. The median age for this group was 12 years (range 0 to 81 years) as compared to 18 years (range 0 to 97 years) for the rest of Canada.

Note : Previous analyses on underlying medical conditions were preliminary. Updates from some provinces and territories to the national abbreviated line-list received in the last two weeks reflect the current situation.

Weekly and cumulative numbers of deaths among
Pandemic (H1N1) 2009 confirmed cases, Canada, to 18 July, 2009

Province/Territory	New deaths reported this week (from July 12 to July 18, 2009)	Cumulative deaths
BC	1	1
AB	0	3
SK	1	4
MB	1	6
ON	2	16
QC	4	18
NB	0	0
NS	0	0
PE	0	0
NL	0	0
YT	0	0
NT	0	0
NU	1	1
Canada	10	49

Overall Influenza Summary - July 12, 2009 to July 18, 2009 (Week 28)

The overall influenza activity increased slightly this week ; the national ILI consultation rate (27 consultations per 1,000 visits vs. 21), the reported activity level (7 regions reported localized activity vs. 4) and the proportion of specimen tested positive for Pandemic (H1N1) 2009 (98.7% vs 95.1%) are higher compared to the last week. However, the proportion of influenza positive tests decreased for the fifth consecutive week.

Seven regions in ON, QC, NS & NL reported localized activity, 40 regions sporadic activity in BC, AB, SK, MB, ON, QC, NB, NS, PEI, NL & NT and 4 regions in NB, NL & YK reported no activity (No report received from NU). Five new influenza outbreaks were reported this week; one in hospital (NL), two in long-term care facilities (ON & QC), one in a workplace (NS) and one occured in unspecified locations (ON).

Map of overall Influenza activity level
by provinces and territories, Week 28 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 was 27 consultations per 1,000 patient visits (see ILI graph) which represents an increase compared to the previous week. The sentinel response rate was 74.6%.

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).
* Data arriving late may cause variations from results seen in previous weeks.

Paediatric Influenza Hospitalizations and deaths

In week 28, 13 laboratory-confirmed influenza-associated paediatric hospitalizations were reported through the Immunization Monitoring Program Active (IMPACT) network. 46% of this week hospitalizations are due to Pandemic (H1N1) 2009 and 54% to seasonal influenza A. To date this season, 724 hospitalizations have been reported; 310 (42.8%) of hospitalizations have been due to Pandemic (H1N1) 2009. The proportion of cases to date by age group are as follows: 12.6% were 0-5 month olds; 25.8% were 6-23 month olds; 21.4% were 2-4 year olds; 19.3% were 5-9 year olds; and 20.9% were 10-16 year olds. The distribution of cases to date by province are as follows: 6.9% from BC, 8.6% from AB, 3.3% from SK, 12.3% from MB, 26.1% from ON, 40.6% from QC, 1.8% from NS & 0.4% from NL. There were four deaths reported so far this season including two deaths due to Pandemic (H1N1) 2009.

Laboratory Surveillance Summary

This week, the proportion of tests that were positive for influenza was 11.3% which is decreasing for the fifth consecutive week (see table). The majority (81.9%) of influenza virus detections this season have been for influenza A. A total of 706 specimen tested positive for influenza this week (all influenza A). Of the 380 influenza A subtyped, 98.7% were due to Pandemic (H1N1) 2009, 1.0% to A(H1) virus and 0.3% to A(H3) virus.

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

Weekly & Cummulative numbers of positive influenza specimens , by Provincial Laboratories

Reporting  provinces	Weekly						Cumulative
	Influenza A					B	Influenza A					B
	A Total	A(H1)	A(H3)	Pand (H1N1)	A (NS)*	Total	A Total	A(H1)	A(H3)	Pand (H1N1)	A (NS)*	Total
BC	93	0	0	43	50	0	1310	9	9	293	999	210
AB	214	0	0	108	106	0	2658	0	8	528	2122	467
SK	31	2	1	23	5	0	1345	31	79	817	418	219
MB	26	0	0	26	0	0	1037	7	35	739	256	37
ON	149	2	0	59	88	0	6485	146	156	2921	3262	1354
QC	53	0	0	0	53	0	3801	0	0	0	3801	1416
NB	14	0	0	0	14	0	317	3	3	22	289	95
NS	120	0	0	110	10	0	442	23	23	317	79	60
PE	0	0	0	0	0	0	26	5	0	7	14	9
NL	6	0	0	6	0	0	183	11	4	45	123	26
Canada	706	4	1	375	326	0	17604	235	317	5689	11363	3893

Note: 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.
* Not subtyped

Antigenic Characterization

* No update received by NML this week.

NML has antigenically characterized 175 Pandemic (H1N1) 2009 isolates by HI assay. The results reveal that these viruses are antigenically related to A/California/7/2009 (H1N1), which is the variant reference virus selected by WHO as a potential candidate for Pandemic (H1N1) 2009 vaccine. Antigenic characterization also indicates that these viruses are antigenically and genetically unrelated to seasonal influenza A (H1N1) viruses, which suggests that there is little or no protection to be expected from vaccination with seasonal influenza vaccine.

Antiviral Resistance (from NML)

* No update received by NML this week.

All Pandemic (H1N1) 2009 viruses tested so far have been sensitive to oseltamivir (255 samples) and zanamivir (100 samples) but resistant to amantadine (283 samples).

International update:

Surveillance

ECDC assesses pandemic risks: In a risk assessment published July 20, 2009, the European Centre for Disease Prevention and Control (ECDC) said to expect 20% to 30% of the population to be affected during the next wave of Pandemic (H1N1) 2009, with the attack rate highest in children and young adults. Though it admits uncertainty, the ECDC says a "reasonable" assumption is a hospitalization rate of 1% to 2%. It also estimates a case-fatality rate of 0.1% to 0.2% and says, "this pandemic can severely stress healthcare systems". [CIDRAP 20Jul09]

Southern Hemisphere

• Australia : As of July 22, 2009, Australia has 14,703 confirmed cases (2,741 new cases since July 17th) and 41 deaths. There are currently 226 people (up 24 since July 17th) in hospital across Australia with Pandemic A(H1N1) 2009, and 93 (41%) of these are in intensive care units (total hospitalizations 1,662).
• New Zealand: As of July 21, 2009, the total number of confirmed cases in New Zealand is 2,443 (up from 2,368 on July 20th), and 11 deaths. A total of 74 people are currently reported to be in hospital, with 26 of these in the ICU. There has been a continuing sharp increase in consultations for ILI, approximately 4-fold the rates seen in the previous 2 years. Of laboratory influenza detections for the week of July 6-12, 58% were Pandemic A(H1N1), 37.5% were influenza A, 4% were seasonal A(H1N1), and <0.5% were seasonal influenza A(H3N2).
• South Africa: As of July 17, South Africa reported a total of 119 cases of Pandemic A(H1N1) 2009. For the week ending July 12, influenza isolates from all surveillance sources were detected in the following proportions: 86% A(H3N2), 7% Pandemic A(H1N1), 6% influenza A (awaiting typing), 2% influenza B, and <1% seasonal influenza A(H1N1).
  • NICD <http://www.nicd.ac.za/>
• Argentina: As of July 14, a total of 3,056 cases of Pandemic A(H1N1) 2009, and 137 deaths have been reported.
• Chile: As of July 20, the number of cases increased to 11,293, 6.3% of cases have been hospitalized, and 68 have died (an increase of 28 cases since July 17, now 0.6% of confirmed cases). Sixty-one percent of cases are in children, 0-19 years, with an increasing proportion this week of cases under 5 years old. The rate of severe respiratory illness is greatest for children under 1 year, at 30 per 100,000.

Northern Hemisphere

• Japan: As of July 22, 2009, Japan reports 4,462 confirmed cases (up 799 since July 17) of Pandemic A(H1N1) 2009 and no deaths.
• United States: As of July 17, 2009, the CDC reports 40,617 confirmed and probable infections with Pandemic A(H1N1) influenza and 263 deaths. During April 15, 2009 to July 11, 2009, the following preliminary laboratory-confirmed overall influenza associated hospitalization rates were reported by the EIP (rates include type A, type B, and Pandemic (H1N1) 2009): Rates for children aged 0-23 months, 2-4 years, and 5-17 years were 1.7, 0.7, and 0.6 per 10,000, respectively. Rates for adults aged 18-49 years, 50-64 years, and >= 65 years were 0.3, 0.3, and 0.3 per 10,000, respectively. During the week of July 5-11, 2009, over 99% of all subtyped influenza A viruses being reported to CDC were pandemic (H1N1) viruses.
• United Kingdom: As of July 23, 2009, the provisional number of deaths related to pandemic (H1N1) 2009 in the UK is 26. The figure is the same as last week because some unrelated deaths have been removed and others added. Pandemic (H1N1) 2009 hospitalizations in England: 840 patients. In week 29 (ending 19 July), GP consultation rates for flu-like illness continued to increase sharply in England. The consultation rate is 155 per 100,000 compared with 73.4 per 100,000 in the previous week. The Health Protection Agency estimates that there were 100,000 new cases of pandemic (H1N1) 2009 in England last week (range 60,000 - 140,000).

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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