January 3, 2009 to January 9, 2010 (Week 1)

Posted 2010-01-15

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Pandemic (H1N1) 2009 virus Surveillance and Epidemiology

A total of 8,537 hospitalized cases including 1,433 (16.8%) cases admitted to ICU and 418 (4.9%) deaths of Pandemic (H1N1) 2009 were reported to PHAC since the beginning of the pandemic. Among the 1,088 ICU cases who had detailed information regarding ventilation status, 58% (n=634) required ventilation. Core data was available for 8,053 (94.3%) hospitalizations, 1,433 (100%) ICU admissions and 414 (99.0%) deaths. Five of the 13 provinces and territories continued to report severe cases with Pandemic (H1N1) 2009 during the last week, however the hospitalized cases (18), ICU admissions (7) and deaths (2) were very low during week 1 compared to the previous weeks. The peak periods of reported laboratory-confirmed hospitalizations and deaths occurred from weeks 22 to 24 (May 31, 2009 to June 20, 2009) for the first wave and from weeks 43 to 45 (October 25, 2009 to November 14, 2009) for the second wave.

Among the children admitted to hospital (0-19 years of age), adults (20 to 64) and seniors (65 and over), chronic pulmonary disease (including asthma) was the most commonly reported underlying medical condition (27.3%, 37.2% and 49.8%, respectively). The other underlying medical conditions associated with risk of admission to hospital were slightly different for seniors, adults and children. Immunosuppression (including cancer) (7.2%) was frequently reported among children admitted to hospital, while adults were affected by diabetes (19.6%). Among hospitalized seniors, chronic heart disease (44.6%) was most commonly reported. Since the beginning of the pandemic, 262 pregnant women have been hospitalized with Pandemic (H1N1) 2009 among 1,277 hospitalized women aged between 15 and 44 years of age. Information on pregnancy trimester was available for 68 out of 262 (26.0%) hospitalized pregnant women reported since the beginning of the pandemic and approximately 2/3 of them (64.7%) were in their third trimester. The most frequently reported underlying medical conditions among hospitalized pregnant women were chronic pulmonary disease (including asthma) (21.4%), diabetes (6.0%) and anemia or hemoglobinopathy (4.7%).

From April 12, 2009 to January 9, 2010, 589 reported hospitalized cases (7.4%) were among people of Aboriginal origin (423 First Nations, 106 Inuit, 46 Metis and 14 with unknown Aboriginal subgroup). This represents an underestimate since ON and NS do not report on Aboriginal status and Aboriginal populations in these two provinces account for 23% of the total Canadian Aboriginal population. Among 423 First Nations cases, 175 were from MB, 127 from AB, 53 from QC, 28 from BC, 21 from NT, 8 from YT, 7 from SK and 4 from NB. The 77 lab-confirmed hospitalized cases from Nunavut were assumed to be persons of Inuit ethnicity as the majority of the population in this territory is Inuit. Other Inuit cases were reported from QC (12), NT (10), AB (4), MB (1), NL (1) and YT (1). Métis cases were from AB (27), MB (16), BC (1), NL (1) and NT (1). To date in the second wave, the proportion of people of Aboriginal origin continued to be lower among all levels of severity of illness (hospitalizations, ICU admission and deaths) compared to the first wave.

Weekly and cumulative numbers of hospitalized cases, ICU admissions and deaths among Pandemic (H1N1) 2009 confirmed cases, Canada, to January 9, 2010†

*Based on reporting date. ** Based on epidemiological date, hospitalization date and reporting date. 1 These provinces reported aggregate counts this week. 2 Note change in total hospitalizations from last week's report: duplicates were removed. † Note that due to reporting delays, some PTs reported retrospectively on first wave cases.
Province/Territory	Week 1 (Jan. 3, 2010-Jan. 9, 2010)*			From August 30, 2009 to January 9, 2010**			From April 12, 2009 to August 29, 2009**
	Hospitalized cases	ICU admissions	Deaths	Hospitalized cases	ICU admissions	Deaths	Hospitalized cases	ICU admissions	Deaths
BC1	2	1	1	997	132	49	52	20	6
AB	4	1	1	1139	208	63	129	29	7
SK	4	4	0	43	39	11	23	12	4
MB	0	0	0	150	18	4	223	43	7
ON	7	1	0	1414	239	96	389	68	25
QC	0	0	0	2483	360	81	572	104	27
NB1,2	--	--	0	161	33	8	2	1	0
NS	1	0	0	272	42	6	17	8	1
PE	0	0	0	49	9	0	1	0	0
NL	0	0	0	274	51	18	3	1	0
YT	0	0	0	15	3	3	0	0	0
NT	0	0	0	46	7	1	6	0	0
NU	0	0	0	5	0	0	72	6	1
Canada	18	7	2	7048	1141	340	1489	292	78

Descriptive characteristics of laboratory-confirmed Canadian Pandemic (H1N1) 2009 hospitalized cases, ICU-admitted cases and deaths with core information available, reported to PHAC as of January 9, 2010^†

	From April 12 to August 29, 2009			From Aug. 30, 2009 to Jan. 9, 2010			Cumulative: From April 12, 2009 to Jan. 9, 2010
	Hospitalized cases (n=1,489)	ICU-admitted (n=292)	Deaths (n=78)	Hospitalized cases (n=6,564)	ICU-admitted  (n=1,141)	Deaths (n=336)	Hospitalized cases (n=8,053)	ICU-admitted (n=1,433)	Deaths (n=414)
Females, %	51.3	57.2	62.8	49.7	49.6	47.3	50.0	51.2	50.2
Median age	23.0	37.0	51.0	30.0	47.0	54.0	29.0	46.0	53.0
Aboriginal status1, %	20.2	16.1	11.5	4.4	6.0	6.3	7.3	8.0	7.2
Underlying medical conditions2, %	46.8 (646/1,380)	58.2 (159/274)	71.1 (54/76)	53.2 (1,710/3,217)	63.0 (563/893)	77.1 (219/284)	51.3 (2,356/4,597)	61.9 (722/1,167)	75.8 (273/360)
Pregnancy3, %	28.0 (77/275)	19.7 (15/76)	28.6 (4/14)	18.5 (185/1,002)	8.5 (15/176)	0.0	20.5 (262/1,277)	11.9 (30/252)	8.0 (4/50)
1 These proportions are underestimates. 2 Proportion of cases with at least one underlying medical condition (excluding pregnancy) among those for whom the information was available. Missing/unknown information has been removed from all calculations except for data reported on underlying condition from MB and ON, where it was not possible to delineate missing information from absence of underlying condition. For these two provinces, missing information has been included in the denominator. Note that Ontario retrospectively provided information to PHAC on underlying medical conditions of fatal cases. This increased the proportion of underlying medical conditions among deaths. 3 Percent of pregnant women among women 15 to 44 years of age. †Note that due to reporting delays, some PTs reported retrospectively on first wave cases.

Overall Influenza Summary - Week 1 (January 3, 2010 to January 9, 2010)

During week 1, all influenza indicators were either back to baseline or considerably under the expected level for this time of the year. The national ILI consultations rate were significantly below the expected range for this time of the year with 17 consultations per 1,000 patient visits. Only 1.3% of the specimens tested were positive for influenza compared to 16.4% for the respiratory syncytial virus.

In week 1, only one region (in ON) reported localized activity. Thirty-one regions in BC, AB, SK, MB, ON, QC, NB & NS reported sporadic activity, while twenty-two regions reported no activity in AB, ON, QC, NB, PE, NS, NL, YT & NT. No influenza outbreaks were reported this week.

Map of overall Influenza activity level by provinces and territories, Week 1, 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, 2009-2010 (N=54)

† sub-regions within the province or territory as defined by the provincial/territorial epidemiologist. Graph may change as late returns come in.

Overall Number of Influenza Outbreaks, Canada, by Report Week, 2009-2010

Note that this was the first year that all the provinces and territories were reporting on influenza outbreaks in schools (greater than 10% absenteeism on any day most likely due to ILI) which has increased considerably the total number of outbreaks reported compared to previous years.

ILI consultation rate

During week 1, the national ILI consultations rate was 17 consultations per 1,000 patient visits (see ILI graph) which was significantly below the expected range for this time of the year. All provinces and territories had either similar or lower ILI consultation rates compared to their respective ILI rates in the previous week. Those under 20 years of age still had the highest consultation rates, with 49 and 21 per 1,000 patient visits among children under 5 years of age and among those 5 to 19 years of age, respectively.

Influenza-like illness (ILI) consultation rates, Canada, by report week,
2009-2010 compared to 1996/97 through to 2008/09 seasons

Note: No data available for mean rate in previous years for weeks 19 to 39 (1996-1997 through 2002-2003 seasons).
Delays in the reporting of data may cause data to change retrospectively.

Paediatric Influenza Hospitalizations and Deaths

In week 1, no laboratory-confirmed influenza-associated paediatric hospitalizations were reported through the Immunization Monitoring Program Active (IMPACT) network. 1,328 hospitalizations have been reported since week 17 (April 26): 97.1% of these hospitalizations were due to Pandemic (H1N1) 2009. Since the beginning of the pandemic, eleven paediatric deaths due to Pandemic (H1N1) 2009 were reported through the IMPACT network among children 16 years of age or under.

Laboratory Surveillance Summary

The proportion of tests that were positive for influenza was 1.3% during week 1 which represented a significant decrease since the peak observed during week 44 (see Tests table). All provinces had a lower proportion of positive tests for influenza compared to the previous week except ON and PEI. During week 1, a total of 41 specimens tested positive for influenza (40 A and 1 B) and 100% of the positive influenza A subtyped specimens were Pandemic (H1N1) 2009. Note that QC reported 44 positive specimen for A/H3N2 and 7 specimen for influenza B since August 30, 2009.

The proportion of positive respiratory syncytial virus tests was 16.4% during week 1 which was higher than the proportion observed for positive influenza tests over the past weeks. The proportion of positive parainfluenza tests was also slightly higher than the proportion of positive tests for influenza.

Influenza tests reported and percentage of tests positive, Canada,
by report week, 2009-2010

Percent positive influenza tests, compared to other respiratory viruses, Canada,
by reporting week, 2009-2010

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

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
Reporting provinces	Weekly (Jan. 3 to Jan. 9, 2010)						Cumulative (Aug. 30, 2009 to Jan. 9, 2010)
	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	6	0	0	6	0	0	6368	0	1	5802	565	0
AB	4	0	0	3	1	0	5858	2	5	5753	98	0
SK	1	0	0	1	0	0	2598	0	1	2298	299	0
MB	7	0	0	6	1	0	1914	0	0	1787	127	0
ON	16	0	0	8	8	0	7891	2	0	3547	4342	4
QC	5	0	0	5	0	1	10684	1	44	10639	0	7
NB	0	0	0	0	0	0	1854	1	1	1833	19	1
NS	1	0	0	0	1	0	783	0	0	751	32	0
PE	0	0	0	0	0	0	103	0	0	101	2	0
NL	0	0	0	0	0	0	951	0	0	951	0	0
Canada	40	0	0	29	11	1	39004	6	52	33462	5484	12
Specimens from NT, YT, and NU are sent to reference laboratories in other provinces

Sale of antivirals (AV) in Canada

During week 1, antiviral prescriptions monitoring results demonstrated a levelling-off in antiviral prescriptions among most provinces and territories. The upward trend reported in Saskatchewan last week appears to be short-lived. An analysis of antiviral data at the Health Region level demonstrates low antiviral prescription rates among all Health Regions for the week of January 3, 2010 to January 9, 2010. No Health Region reported an antiviral rate greater than 2.5 antivirals/1000 other prescriptions.

Reference: H1N1 Antiviral and OTC Surveillance Weekly Report. CFEZID, PHAC.

Canadian situation

Antigenic Characterization

Since September 1, 2009, the National Microbiology Laboratory (NML) has antigenically characterized 717 Pandemic (H1N1) 2009 viruses and 10 seasonal influenza viruses (2 influenza A/H1N1, 7 H3N2, and 1 B virus) that were received from Canadian laboratories. Of the 717 Pandemic (H1N1) 2009 viruses characterized, 713 (99.34) were antigenically related to A/California/7/2009, which is the pandemic reference virus selected by WHO as the Pandemic (H1N1) 2009 vaccine. Four viruses (0.6%) tested showed reduced titer with antisera produced against A/California/7/09. Of the seven seasonal influenza A (H3N2) viruses characterized, one was related to A/Brisbane/10/07, which is the influenza A/H3N2 component recommended for the 2009-10 influenza vaccine and six viruses were antigenically related to A/Perth/16/09, which is the WHO recommended influenza A (H3N2) component for the 2010 Southern Hemisphere vaccine.

Antiviral Resistance

NML: Pandemic (H1N1) 2009 viruses tested so far have been sensitive to zanamivir (807 samples) but resistant to amantadine (831 samples).

NML/Provinces: Ten cases of oseltamivir resistant Pandemic (H1N1) 2009 were reported to date in Canada: one in Alberta, one in Manitoba, five in Ontario, two in Quebec, and one in New Brunswick. Nine of the ten resistant cases were associated with oseltamivir treatment. One case (NB) appeared to be the result of infection with an antiviral-resistant strain of H1N1.

International update

Global information

WHO: Worldwide more than 208 countries and overseas territories or communities have reported laboratory confirmed cases of Pandemic (H1N1) 2009, including at least 12,799 deaths. Overall, Pandemic (H1N1) 2009 transmission was most active in parts of central, eastern and southeastern Europe (Poland, Serbia, Ukraine, Georgia), North Africa (Egypt), and South Asia (northern India, Nepal, and in Sri Lanka). Specifically, in the temperate regions of the northern hemisphere, transmission of Pandemic (H1N1) 2009 remained geographically widespread, however overall disease activity has recently peaked or has past its peak in much of the hemisphere. In the temperate regions of the southern hemisphere, sporadic cases of pandemic influenza continued to be reported without evidence of sustained community transmission. <http://www.who.int/csr/don/2010_01_08/en/index.html>

Antiviral resistance: To date, 190 Pandemic (H1N1) 2009 isolates worldwide have been found to be resistant to oseltamivir, all with the same H275Y mutation. <http://www.who.int/csr/disease/swineflu/laboratory08_01_2010/en/index.html>

Geographic update

United States: During week 52 (December 27, 2009 – January 2, 2010), influenza activity decreased slightly in the United States. Widespread activity was reported by one state; one state reported no influenza; and the remaining states reported regional, local, and sporadic influenza activity. ILI physician consultations decreased this week over last week and overall hospitalization rates for this season were unchanged from the previous week in all age groups. The proportion of deaths attributed to pneumonia and influenza was below the epidemic threshold. Another four flu-related pediatric deaths were reported this week: all four were associated with laboratory confirmed pandemic (H1N1) 2009. All subtyped influenza A viruses reported to CDC were 2009 influenza A (H1N1) viruses. <http://www.cdc.gov/flu/weekly/ and http://www.cdc.gov/h1n1flu/update.htm>

Europe: For week 53/2009 (Dec. 28, 2009- Jan 3, 2010), all reporting countries (19 out of 29) experienced low influenza activity while Estonia, France, Ireland, Romania, Scotland reported medium intensity. France, Slovenia and Wales reported widespread activity. All countries reported a decreasing trend or stable activity. Of the 19 countries reporting in week 53, all but Cyprus, Portugal, Romania, Northern Ireland and Wales have observed decreasing ILI/ARI rates for at least the last two weeks, with 11 countries and England and Scotland reaching levels below those reported in week 40. The 2009/10 season has been characterized by influenza activity above baseline levels earlier than in recent seasons. In addition, peak incidences of ILI and/or ARI have generally been higher this season. Where information on the age of patients is collected, individuals younger than 15 years have been the most affected age group. While the proportion of influenza-positive sentinel samples continued to decline, the Pandemic (H1N1) 2009 still accounted for nearly 100% of all subtyped viruses in sentinel and severe acute respiratory infection (SARI) patients. The number of SARI cases, measured by week of onset, continued to decline. As of 11 January, 2010, the cumulative number of reported deaths since the beginning of the pandemic in EU/EFTA Member States has totalled 2,152.
<http://ecdc.europa.eu/en/healthtopics/Documents/100111_Influenza_AH1N1_Situation_Report_0900hrs.pdf and http://ecdc.europa.eu/en/activities/surveillance/EISN/Newsletter/
100108_EISN_Weekly_Influenza_Surveillance_Overview.pdf>

Asia: Influenza transmission remained active but may have already peaked in west Asia. Pandemic influenza transmission remained geographically regional to widespread in southeast Asia and geographically widespread in south Asia where an increased trend of respiratory diseases activity was reported (northern India, Nepal, Sri Lanka, Thailand). In east Asia, influenza transmission remained widespread and active but appeared to be declining overall. Influenza/ILI activity continued to decline in Japan, in northern and southern China, Chinese Taipei, and Hong Kong SAR (China). Pandemic H1N1 was the predominant circulating virus but seasonal H3N2 viruses continued to circulate in very small numbers in northern China. Slight increases in rates of ILI were again reported in Mongolia. Activity in central Asia has declined and recently peaked in Uzbekistan and Kyrgyzstan. <http://www.who.int/csr/don/2010_01_08/en/index.html>

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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).

ILI definition for the 2009-2010 season
ILI in the general population: Acute onset of respiratory illness with fever and cough and with one or more of the following - sore throat, arthralgia, myalgia, or prostration which could be due to influenza virus. In children under 5, gastrointestinal symptoms may also be present. In patients under 5 or 65 and older, fever may not be prominent.

Definitions of ILI/Influenza outbreaks for the 2009-2010 season
Schools: greater than 10% absenteeism on any day most likely due to ILI.
Hospitals and residential institutions: two or more cases of ILI within a seven-day period, including at least one laboratory confirmed case. Institutional outbreaks should be reported within 24 hours of identification. Residential institutions include but not limited to long-term care facilities (LTCF), prisons.
Other: two or more cases of ILI within a seven-day period, including at least one laboratory confirmed case; i.e. workplace, closed communities.

Influenza Activity levels are defined as:
1 = No activity: i.e. no laboratory-confirmed influenza detections during the past four weeks, however, sporadically occurring ILI may be reported
2 = Sporadic: sporadically occurring ILI and lab confirmed influenza* with NO outbreaks detected within the influenza surveillance region†
3 = Localized: sporadically occurring ILI and lab confirmed influenza* together with outbreaks of ILI in schools and worksites or laboratory confirmed influenza in residential institutions occurring in less than 50% of the influenza surveillance region(s)†
4 = Widespread: sporadically occurring ILI and lab confirmed influenza* together with outbreaks of ILI in schools and worksites or laboratory confirmed influenza in residential institutions occurring in greater than or equal to 50% of the influenza surveillance region(s)†
* confirmation of influenza within the surveillance region at any time within the prior four weeks
† sub-regions within the province or territory as defined by the provincial/territorial epidemiologist

We would like to thank all the Fluwatch surveillance partners who are participating in this year's influenza surveillance program.
This report is available on the Public Health Agency website at the following address: http://www.phac-aspc.gc.ca/fluwatch/index.html. Ce rapport est disponible dans les deux langues officielles. Pour en recevoir un exemplaire dans l'autre langue chaque semaine, veuillez communiquer avec Estelle Arseneault, Division de l'immunisation et des infections respiratoires au (613) 952-8484

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Definitions for the 2009-2010 season