September 27, 2009 to October 3, 2009 (Week 39)

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Pandemic (H1N1) 2009 virus Surveillance and Epidemiology

A total of 1,504 hospitalized cases including 295 (19.6%) cases admitted to ICU and 155 (10.3%) cases required ventilation as well as 78 deaths of Pandemic (H1N1) 2009 were reported to PHAC as of October 3, 2009. The proportion of females affected, the median age and the proportion of cases with underlying medical conditions was still increasing with severity of illness this week (see Characteristics table). Aboriginals were over-represented amongst those who were hospitalized or admitted to ICU. They account for 3% of the national population; however, 18% of hospitalizations, 16% of cases admitted to ICU and 13% of deaths were in this group. Aboriginal communities have higher prevalence of underlying conditions than the general Canadian population which may explain partially the elevated rates in this population. Pregnant women also had a higher burden of morbidity and mortality. Assuming 1% of the population is pregnant in a given year, approximately 5% of hospitalized cases and 5% of deaths occurred in this group. The median difference between symptom onset date/specimen collection and date of hospitalization increased with severity of illness; 3.0 days for all hospitalized cases compared to 4.0 and 5.0 for ICU-admitted cases and deaths, respectively.

The national hospitalization rate was 4.5 per 100,000 population with the highest rates in children aged less than 15 years of age (10.6 per 100,000). The national mortality rate was 0.23 per 100,000 population; those 45 years and older had the highest mortality rate (0.34 per 100,000). ICU admission rate and ventilation rate were also elevated in children under five years of age (1.6 and 1.1 per 100,000, respectively).

Amongst all laboratory-confirmed hospitalized cases, 269 (17.9%) were Aboriginal (162 First Nations, 80 Inuit, 19 Metis and 8 unknown ethnicity). Approximately 46% of the hospitalized cases among those of First Nations ethnicity were living on a reserve. Cases among all Inuit including those from Nunavut had higher hospitalization rates compared to the First Nations population (158.5 vs. 23.2 per 100,000) and higher mortality rates (4.0 vs 0.7 per 100,000) (caution: rate based on small fatality numbers reported). However, hospitalized cases from Nunavut and those that were Inuit were younger (median age 4.5 years vs. 19.0 years), admitted to ICU less frequently (11.3% vs. 20.4%), required ventilation less frequently (3.8% vs. 17.9%) and had fewer underlying medical conditions (31.9% vs. 65.4%) compared to First Nations hospitalized cases.

Weekly and cumulative numbers of hospitalizations, ICU admissions and deaths among
Pandemic (H1N1) 2009 confirmed cases, Canada, to 3 October, 2009

Province/Territory	This week			Cumulative
	Hospitalized cases	ICU admissions	Deaths	Hospitalized cases	ICU-admitted cases	Deaths
BC	12	1	0	64	22	6
AB	2	1	0	131	31	8
SK	0	0	0	24	12	4
MB	5a	0	0	226	43	7
ON	6	1	0	380	66	24
QC	0	0	0	580	104	27
NB	0	0	0	2	1	0
NS	0	0	0	17	8	1
PE	0	0	0	1	0	0
NL	0	0	0	3	1	0
YT	0	0	0	0	0	0
NT	0	0	0	10	1	0
NU	0	0	0	66	6	1
Canada	25	3	0	1504	295	78
a Due to reporting delays between PHAC and the province, the new numbers reflect the situation since week 36.

 

Descriptive characteristics of laboratory-confirmed Canadian Pandemic (H1N1) 2009 hospitalized cases, cases admitted to ICU and deaths with core information available, reported to the Public Health Agency of Canada as of 3 October 2009

1 Proportion of cases with at least one underlying medical condition (excluding pregnancy) among those for whom the information was available. 2 Percent of pregnant women among women 15 to 44 years of age.
	Hospitalizated cases (n=1,504)	Cases admitted to ICU (n=295)	Deaths (n=78)
Females, %	51.5	57.3	60.3
Median age	23	37	50
Aboriginal status, %	17.9	15.6	12.8
Underlying medical conditions1, %	61.7 (613/994)	71.8 (158/220)	81.7(49/60)
Pregnancy2, %	27.6 (78/283)	19.0 (15/79)	28.6 (4/14)

Overall Influenza Summary - Week 39 (September 27 to October 3, 2009)

The overall influenza activity slightly increase for a third consecutive week and was higher than expected for this time of the year. The total number of influenza outbreaks was high this week with 40 outbreaks in schools. The national ILI consultation rate was slightly higher compared to the previous weeks. However, the proportion of positive tests for influenza remained stable low during week 39.

Five regions reported widespread activity in BC & NT and four regions in BC, ON & NB reported localized activity, while twenty-nine regions reported sporadic activity in BC, AB, SK, ON, QC, NB, PEI, NS, NL, YK & NU and sixteen regions in MB, QC, NB, NS & NL reported no activity. Fourty influenza outbreaks in schools were reported this week in BC (18), NT (16), ON (3), SK (1), NB (1) and NS (1). Note that this is the first year that all the provinces and territories are reporting on influenza outbreak in schools (greater than 10% absenteeism on any day most likely due to ILI).

Map of overall Influenza activity level
by provinces and territories, Week 39, 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

ILI consultation rate

This week, the national ILI consultation rate was 36 consultations per 1,000 patient visits (see ILI graph) which is slightly higher compared to the previous weeks and above the expected range for this time of the year. The sentinel response rate was 89.3%. Five provinces (SK, ON, NL, YK and NT) had higher ILI consultation rates compared to their ILI rates in previous weeks. The ILI rates of these five provinces were also higher than the national level this week. People under 20 years of age had the highest consultations rates with 65.2 and 67.6 per 1,000 patient visits among children under 4 years of age and between 5 and 19 years of age, respectively.

Influenza-like illness (ILI) consultation rates, Canada, by report week,
2009-2010 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).
*Delays in the reporting of data may cause data to change restrospectively.

Paediatric Influenza Hospitalizations and deaths

In week 39, three laboratory-confirmed influenza-associated paediatric hospitalizations were reported through the Immunization Monitoring Program Active (IMPACT) network. Two hospitalizations reported this week were due to seasonal influenza A and one Pandemic (H1N1) 2009. 381 hospitalizations had been reported since week 17 (April 26); 92.4% of these hospitalizations were due to Pandemic (H1N1) 2009. Since the beginning of the pandemic, four deaths due to Pandemic (H1N1) 2009 had been reported through the IMPACT network among children under 16 years of age.

Laboratory Surveillance Summary

This week, the proportion of tests that were positive for influenza was 3.8% which remained similar to the previous week (see Tests table). British Columbia had again this week a high proportion of positive tests for influenza with approximatively 15%. A total of 231 specimens tested positive for influenza this week (all A). This week, 96.9% of the positive influenza A subtyped specimens were Pandemic (H1N1) 2009.

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

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. * Not subtyped
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	148	0	0	129	19	0	458	0	0	292	166	0
AB	38	0	0	18	20	0	182	0	0	42	140	0
SK	2	0	0	2	0	0	20	0	0	19	1	0
MB	1	0	0	0	1	0	4	0	0	1	3	0
ON	31	5	0	6	20	0	89	6	0	22	61	0
QC	8	0	0	0	8	0	46	0	0	0	46	0
NB	0	0	0	0	0	0	5	0	1	2	2	0
NS	3	0	0	2	1	0	11	0	0	7	4	0
PE	0	0	0	0	0	0	3	1	0	2	0	0
NL	0	0	0	0	0	0	2	0	0	2	0	0
Canada	231	5	0	157	69	0	820	7	1	389	423	0

 

Sale of antivirals (AV) in Canada

In week 39, compared to other prescriptions filled in Canada, the sale of AV suggested continued increases in most Provinces/Territories. The most pronounced increases were in British Columbia and among children.

Reference: H1N1 Antiviral and OTC Surveillance Weekly Report. For more information including a copy of the report, please contact Frank Pollari 519-826-2184, Frank_Pollari@phac-aspc.gc.ca.

Canadian situation

Antigenic Characterization

Since September 1, 2009, NML has antigenically characterized five influenza A viruses that was received from Canadian Laboratories. The five Pandemic (H1N1) 2009 characterized were antigenically related to A/California/7/2009, which is the pandemic reference virus selected by WHO as a potential candidate for Pandemic (H1N1) 2009 vaccine. WHO recommended composition of influenza virus vaccines for use in the 2010 southern hemisphere influenza season is as follow: an A/California/7/2009 (H1N1)-like virus, an A/Perth/16/2009 (H3N2)-like virus and a B/Brisbane/60/2008-like virus.

Antiviral Resistance

NML: The five Pandemic (H1N1) 2009 specimens had been tested for resistance to neuraminidase inhibitors (oseltamivir and zanamivir) by phenotypic assay and/or sequencing. The testing results showed that the virus was sensitive to oseltamivir and zanamivir.

Provinces: Two cases of oseltamivir resistant Pandemic (H1N1) 2009 were reported to date in Canada from the province of Quebec on July 21, 2009 and from the province of Alberta on September 15, 2009.

International update

Global information

• WHO: As of 27 September 2009, over than 4,100 deaths of Pandemic (H1N1) 2009 were reported to WHO. In the temperate regions of the southern hemisphere, influenza transmission has largely returned to baseline or has declined substantially. In the temperate regions of the northern hemisphere, influenza-like-illness (ILI) activity continued to increase in many areas. In Europe and Central and Western Asia, Israel, France, and the United Kingdom (Northern Ireland) were reporting increases in ILI activity. Tropical regions of the Americas and Asia were still reporting regional to widespread geographic spread of influenza activity but the trends in respiratory diseases activity were mixed. Pandemic (H1N1) 2009 was the predominant influenza strain worldwide. <http://www.who.int/csr/don/2009_10_02/en/index.html>

Northern Hemisphere

• United States: During week 38 (September 20-26, 2009), influenza activity remained elevated in the U.S. The proportion of outpatient visits for influenza-like illness (ILI) was above the national baseline. Twenty-seven states reported geographically widespread influenza activity. From August 30-September 26, 2009, 16,174 hospitalizations and 1,379 deaths associated with influenza virus infection or based on syndromic surveillance for influenza and pneumonia, were reported to CDC. Even with increasing numbers of deaths, the proportion of deaths attributed to pneumonia and influenza was below the epidemic threshold.
  <http://www.cdc.gov/flu/weekly/>
• Mexico: As of October 6, 2009, Mexico reported 35,838 confirmed cases of Pandemic (H1N1) 2009, and 245 deaths. Daily diagnoses reached higher levels in September than the Pandemic (H1N1) 2009 peak in April, with 600 new cases in just one day this month alone.
  <http://portal.salud.gob.mx/contenidos/noticias/influenza/estadisticas.html>
• United Kingdom: As of October 1, 2009, pandemic influenza activity continues to increase across the UK, particularly in school-aged children. Health Protection Agency modelling gave an estimate of 14,000 (range 7000 – 30,000) new cases in England in week 39. The estimated number of new cases has increased in all regions and age groups. The main influenza virus circulating in the UK continues to be the Pandemic (H1N1) 2009, with few influenza H1 (non-pandemic), H3 and B viruses detected. The majority of pandemic influenza cases continue to be mild. The cumulative number of deaths reported due to Pandemic (H1N1) 2009 in the UK is 84. <http://www.hpa.org.uk/web/HPAwebFile/HPAweb_C/1253205561258>
• France: As of October 6, 2009, the Pandemic (H1N1) 2009 virus continues to circulate and influenza activity has remained at previous levels. From September 28 to October 4, 2009 the ILI consultation rate remained stable (217 cases per 100,000 compared to threshold of 102 cases per 100,000). The proportion of positive tests remained low. <http://www.invs.sante.fr>
• Spain: As of October 1, 2009, the number of Pandemic (H1N1) 2009 cases sharply rose and there were an estimated 31,322 new Pandemic (H1N1) cases over the last seven days. The ratio increased to 77.9 cases per 100,000 inhabitants as compared to 52.3 cases per 100,000 inhabitants in the previous week. To date, the cumulative number of deaths reported due to Pandemic (H1N1) 2009 in Spain is 42. <http://www.msps.es/en/servCiudadanos/alertas/informesGripeA/091001.htm>
• China: On October 6, 2009, China reported its first death from the H1N1 flu strain after weeks on alert against the disease. The victim, who died on Sunday, was an 18-year-old woman from the Tibetan autonomous region. (Media report in H1N1 Flu Virus: GPHIN Summary Report Tuesday, 06 October 2009).

Southern Hemisphere

• Australia: National influenza activity continues to decrease. Most jurisdictions have reported that Pandemic (H1N1) 2009 activity is at or near baseline levels. As of October 6, 2009, Australia had 36,927 confirmed cases and 183 deaths. Australian states and territories now report new hospitalizations weekly and for the past week, 36 new hospitalizations were reported. The number of new confirmed Pandemic (H1N1) 2009 cases and hospitalisations has decreased nationally with a number of jurisdictions reporting no new notifications in the last weeks, indicating that the first wave of the pandemic has subsided. <http://www.healthemergency.gov.au/internet/healthemergency/publishing.nsf/Content/
  1E7215C3455F98EECA2576470008CF8C/$File/061009.doc>
• New Zealand: As of October 7, 2009, the total number of confirmed cases in New Zealand was 3,174 and 18 deaths. The influenza activity including Pandemic (H1N1) 2009 was now the same as would be expected at this time of year. The number of GP consultations based on a sample of sentinel practices, continues to decline and is only slightly higher than at the same time in the last two years.
  <http://www.moh.govt.nz/moh.nsf/indexmh/influenza-a-h1n1-news-media>

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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 2009-2010 season