October 25, 2009 to October 31, 2009 (Week 43)

Posted 2009-11-06

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Pandemic (H1N1) 2009 virus Surveillance and Epidemiology

A total of 2,440 hospitalized cases including 443 cases admitted to ICU and 230 cases required ventilation as well as 100 deaths of Pandemic (H1N1) 2009 were reported to PHAC as of October 31, 2009. Since the beginning of the pandemic (April 12, 2009 to October 31, 2009), the national cumulative crude hospitalization rate is 7.3 per 100,000 population and the national cumulative crude mortality rate is 0.3 per 100,000 population. In addition, the national cumulative crude ICU admission and ventilation rates are 1.3 and 0.7 per 100,000 population, respectively. This week’s report provides comparisons of current data and data reported since August 30, 2009 up to October 31, 2009 which can be used as the baseline comparison period (see table below).

Since August 30 up to October 31, 2009, the national crude hospitalization rate is 2.8 per 100,000 population and the national cumulative crude mortality rate is 0.1 per 100,000 population. In addition, the national cumulative crude ICU admission is 0.4 per 100,000 population. This week, October 25 to 31, 2009, the national crude hospitalization rate is 2.0 per 100,000 population and the national cumulative crude mortality rate is 0.02 per 100,000 population. In addition, the national cumulative crude ICU admission is 0.3 per 100,000 population.

There was a considerable increase in the number of hospitalizations and deaths reported during the last week with QC, BC, and ON reporting the highest numbers. The numbers reported during the previous weeks were similar to the peak period of the first wave (e.g. the three first weeks of June, 2009). The greatest numbers of ICU admissions were reported from QC, BC, and AB. Deaths occurred in ON (3), BC (2), AB (2), and NL (1). Since August 30 up to October 31, 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 (see Characteristics table). Comparing the period of up to August 29, 2009 to the period of August 30, 2009 to October 31, 2009, less pregnant women among women of reproductive age and less Aboriginals were hospitalized, admitted to ICU and died during the period ending October 31, 2009.

Weekly and cumulative numbers of hospitalizations, ICU admissions and deaths among
Pandemic (H1N1) 2009 confirmed cases, Canada, to 31 October, 2009

Province/Territory	This week (Oct. 25-31, 2009)*			From August 30, 2009 to October 31, 2009**			From April to August 29, 2009**
	Hospitalized cases	ICU admissions	Deaths	Hospitalized cases	ICU admissions	Deaths	Hospitalized cases	ICU admissions	Deaths
BC1	162	22	2	307	52	9	54	21	5
AB	80	19	2	126	25	6	137	33	8
SK	3	3	0	4	3	1	23	12	4
MB	0	0	0	0	0	0	227	43	7
ON	105	13	3	166	26	7	378	67	23
QC	246	30	0	261	32	0	572	104	27
NB	5	0	0	1	0	0	7	1	0
NS	16	3	0	15	3	0	18	8	1
PE	3	0	0	3	0	0	1	0	0
NL1	27	0	1	27	0	1	3	1	0
YT	4	1	0	4	1	0	0	0	0
NT	10	2	0	34	5	0	6	0	0
NU	0	0	0	0	0	0	66	6	1
Canada	661	93	8	948	147	24	1492	296	76
*Based on reporting date. ** Based on epidemiological date. 1 These two provinces reported aggregate counts this week.

 

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 October 31, 2009

1 Proportion of cases with at least one underlying medical condition (excluding pregnancy) among those for whom the information was available. Note that P/T are now reporting on three additional underlying medical conditions: chronic liver disease, chronic neurological disease and anemia or hemoglobinopathy. 2 Percent of pregnant women among women 15 to 44 years of age.
	From August 30, 2009 to October 31, 2009			From April to August 29, 2009
	Hospitalized cases (n=854)	Cases admitted to ICU (n=147)	Deaths (n=24)	Hospitalized cases (n=1,492)	Cases admitted to ICU (n=296)	Deaths (n=76)
Females, %	52.1	54.4	54.2	51.4	57.4	60.5
Median age	25.0	44.0	48.0	23.0	37.0	51.0
Aboriginal status, %	5.5	4.1	8.3	17.8	14.9	11.8
Underlying medical conditions1 , %	57.1 (208/364)	68.5 (61/89)	76.9 (10/13)	55.9 (469/839)	67.8 (122/180)	73.9 (34/46)
Pregnancy2 , %	19.3 (33/171)	9.7 (3/31)	0.0	22.7 (63/277)	14.1 (11/78)	28.6 (4/14)

 

Overall Influenza Summary - Week 44 (October 25 to October 31, 2009)

Considerable increases in overall influenza activity were reported this week. All indicators (proportion of positive influenza tests, national ILI consultation rate, number of regions reporting widespread activity and number of influenza outbreaks) were considerably higher this week compared to the previous weeks.

Nineteen regions reported widespread activity in BC, AB, SK, ON, NL & NT and sixteen regions in ON, QC, NB, NS, PEI & YK reported localized activity, while eighteen regions reported sporadic activity in MB, QC, NB, NS, NL & NU and one region in NB reported no activity. The 737 influenza outbreaks reported this week were all in schools except 11 in hospitals (NL, ON), 9 in an unspecified location (AB, ON, NL & YK) and 7 in long-term care facility (BC, SK, QC & NL). The schools outbreaks were in AB (361), BC (146), SK (105), NS (66), PEI (16), NB (11), NL (3) and NT (2). Note that this is the first year that all the provinces and territories are reporting on influenza outbreaks in schools (greater than 10% absenteeism on any day most likely due to ILI) which is increasing considerably the total number of outbreaks reported compared to the previous years.

Map of overall Influenza activity level
by provinces and territories, Week 43, 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 111 consultations per 1,000 patient visits (see ILI graph) which is significantly higher compared to the previous weeks and still highly above the expected range for this time of the year. All provinces and territories had higher ILI consultation rates compared to last week except for BC, SK, YK and NT which had similar rates in comparison to the previous week. People under 20 years of age had the highest consultations rates with 293 and 239 per 1,000 patient visits among children under 5 years of age and among those 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 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 restrospectively.

Paediatric Influenza Hospitalizations and deaths

In week 43, 120 laboratory-confirmed influenza-associated paediatric hospitalizations were reported through the Immunization Monitoring Program Active (IMPACT) network. 116 Pandemic (H1N1) 2009 and 4 other hospitalizations due to unsubtyped influenza A were reported this week. 605 hospitalizations had been reported since week 17 (April 26); 95.2% 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 36.3% which is a significant increase compared to the previous weeks (see Tests table). All provinces and territories had a high proportion of positive tests for influenza this week, except British Columbia which had a slightly lower proportion this week. This week, the number of specimen tested positive for influenza was two times higher with 7,970 specimen (all A and 2 B) and the proportion of positive subtyped influenza A specimens that were Pandemic (H1N1) 2009 was 99.7%.

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 (Oct. 25-31, 2009)						Cumulative (Aug. 30-Oct. 31, 2009)
	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	1243	0	1	1239	3	0	3891	0	1	3330	560	0
AB	2254	0	0	0	2254	0	4101	0	0	769	3332	0
SK	487	0	0	443	44	0	700	0	1	605	94	0
MB	53	0	0	37	16	0	93	0	0	71	22	0
ON	1501	1	1	665	834	1	2834	2	1	1442	1389	3
QC	1796	0	11	1785	0	1	2418	1	23	2394	0	1
NB	67	0	0	67	0	0	80	1	1	76	2	1
NS	244	0	0	241	3	0	331	0	0	318	13	0
PE	42	0	0	42	0	0	54	0	0	53	1	0
NL	283	0	0	283	0	0	360	0	0	360	0	0
Canada	7970	1	13	4802	3154	2	14862	4	27	9418	5413	5

 

Sale of antivirals (AV) in Canada

During week 43, compared to other prescriptions filled in Canada, the sale of AV demonstrated an increase in prescription rates in all provinces and territories. From October 25 to October 31, 2009, the top five Health Regions in Canada, from highest to lowest antiviral prescription sales per all other prescription sales (antivirals/1,000 prescription sales) were in Western Newfoundland (88), Northern Alberta (66), Eastern Newfoundland (60), Northeastern British Columbia (56) and Eastern Ontario (49).

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

Canadian situation

Antigenic Characterization

Since September 1, 2009, NML has antigenically characterized 69 Pandemic (H1N1) 2009 viruses and two seasonal influenza viruses (one influenza A/H1N1 and one B virus) that were received from Canadian laboratories. All 69 Pandemic influenza A (H1N1) viruses characterized were antigenically related to A/California/7/2009, which is the pandemic reference virus selected by WHO as Pandemic (H1N1) 2009 vaccine. The one seasonal influenza A/H1N1 virus characterized was related to A/Brisbane/59/07, which is the influenza A/H1N1 component recommended for the 2009-10 influenza vaccine. The one influenza B virus characterized was antigenically related to B/Brisbane/60/08, which is the recommended influenza B component for the 2009-10 influenza vaccine.

Antiviral Resistance

NML: Pandemic (H1N1) 2009 viruses tested so far have been sensitive to zanamivir (69 samples) but resistant to amantadine (52 samples). Of the 68 Pandemic (H1N1) 2009 viruses tested, 66 were sensitive to oseltamivir and two viruses were resistant to oseltamivir with the H275Y mutation. The two resistant cases were associated with oseltamivir treatment.

Provinces: Three cases of oseltamivir resistant Pandemic (H1N1) 2009 were reported to date in Canada from the province of Quebec on July 21, 2009, from Alberta on September 15, 2009 and from Ontario on October 13, 2009.

Other Canadian information

Vaccination

All the provinces and territories have started their vaccination campaigns except Nunavut which will start as of November 1, 2009.

International update

Global information

• WHO: In the temperate zone of the northern hemisphere, influenza transmission continues to intensify marking an unusually early start to winter influenza season in some countries. In Western Europe, high rates of ILI and proportions of respiratory specimens testing positive for Pandemic (H1N1) 2009 have been observed in at least five countries: Iceland, Ireland, the UK (N. Ireland), Belgium, and the Netherlands. Mexico has reported more confirmed cases since September than during the springtime epidemic. Temperate regions of the southern hemisphere have reported no significant Pandemic (H1N1) 2009 influenza activity in the past week.
  Antiviral resistance: To date, 39 resistant pandemic H1N1 influenza viruses have been detected and characterized worldwide. All of these viruses show the same H275Y mutation that confers resistance to the antiviral oseltamivir. <http://www.who.int/csr/disease/swineflu/updates/en/index.html>

Northern Hemisphere

• United States: From October 18 to 24, 2009, the U.S. continued to experience increasing rates of ILI for the ninth consecutive week. This activity now exceeded what was normally seen in the peak of annual influenza seasons. A high proportion (over 42%) of clinical laboratory specimens was positive for influenza A, with these nearly all Pandemic (H1N1) 2009. Forty-eight states reported widespread influenza activity this week, an unprecedented level of activity for seasonal influenza. Influenza hospitalization rates and deaths attributable to influenza and pneumonia continued to increase and were higher than expected for this time of year. From August 30 to October 24, 2009, 12,466 hospitalizations and 530 deaths were reported to CDC for laboratory-confirmed influenza. Since April 2009, there have been 114 confirmed paediatric Pandemic (H1N1) 2009 deaths; 74 of these have been reported to CDC since August 30, 2009. Twenty-two paediatric influenza-related deaths were reported in the past week. <http://www.cdc.gov/flu/weekly/ and http://www.cdc.gov/h1n1flu/update.htm>
• United Kingdom: Pandemic influenza activity continued to increase with the main burden of disease remaining in school-aged children and young adults. Forty-two schools throughout England, and 12 in Northern Ireland, have reported outbreaks of ILI during week 43. There were a total of 1,200 new patients hospitalized in England with suspected Pandemic (H1N1) 2009 in the week from October 22 to 28, 2009 (increased from 884 in the previous week). Health Protection Agency modelling gave an estimate of 78,000 (range 39,000 – 169,000) new cases in England in week 43. <http://www.hpa.org.uk/webw/HPAweb&Page&HPAwebAutoListName/Page/1242949541993?p=1242949541993>
• France: From October 26 to November 1, 2009, Pandemic (H1N1) 2009 circulation increased to 31% of consultations for acute respiratory illness. Despite school holidays, the number of Pandemic (H1N1) 2009 cases was increasing across the country. In large urban centres, Pandemic (H1N1) 2009 was overtaking other seasonal respiratory viruses. The Groupes Régionaux d’Observation de la Grippe (GROG) estimated that the number of cases of influenza in France has increased from 266,000 in week 43 to 341,000 in week 44. <http://www.invs.sante.fr>
• Ukraine: This week, the WHO dispatched a field team to assist in mitigating an epidemic of acute respiratory illness (ARI) and influenza-like illness (ILI) in several regions. Some cases have been confirmed as Pandemic (H1N1) 2009. As of October 30, 2009, over 2,300 individuals had been admitted to hospital, including more than 1,100 children. One hundred and thirty-one cases required intensive care, including 32 children. As of November 2, 2009, a total of 70 deaths had been reported. Preliminary epidemiological data analysis indicated that severe cases and deaths primarily occurred among previously healthy young adults aged 20 – 50 years. There are restrictions on large gatherings. Schools and entertainment establishments have been closed for 3 weeks.

Southern Hemisphere

• Australia: National influenza activity continued to decrease. ILI consultations to GPs and emergency departments as well as absenteeism rates were stable or decreasing. The number of people with Pandemic (H1N1) 2009 requiring hospitalization continued to decrease. Six jurisdictions reported no new hospitalizations in the week ending October 16, 2009. In total, 4,831 people have been hospitalized, with 13% admitted to Intensive Care Units. The overall hospitalization rate was 22.6 per 100,000 population with the highest rates in children aged less than 5 years of age. Pregnant women represented 23% of all hospitalizations for Pandemic (H1N1) 2009 of women aged between 20-39 years. <http://www.healthemergency.gov.au/internet/healthemergency/publishing.nsf/Content/ozflu2009.htm>
• New Zealand: There has been a decrease in consultations for ILI in week 44 (October 26 - November 1, 2009). The highest ILI consultation rates have been reported among children and teenagers aged 0 to 19 years. Next year's seasonal influenza vaccine will contain the Pandemic (H1N1) 2009 strain and be free to extra groups who are at particular risk. <http://www.moh.govt.nz/moh.nsf/indexmh/influenza-a-h1n1-news-media, and http://www.surv.esr.cri.nz/virology/influenza_weekly_update.php>

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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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