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August 30, 2009 to September 5, 2009 (Week 35) |
Fluwatch
Summary of FluWatch Findings for the
Week ending September 5, 2009
- Week 35 marks the start of the 2009-2010 Influenza Season
- The overall trend of influenza activity remains similar to the previous week. The national ILI consultation rate was slightly higher than expected for this time of the year. The peak period of Pandemic (H1N1) 2009 occurred in the first three weeks of June.
- The intensity of Pandemic (H1N1) infection 2009 in the population is low to moderate with only a small number of hospitalizations (n=11) and two deaths reported this week. As of September 5, 2009, a total of 1,445 hospitalized cases, 285 cases admitted to an intensive care unit (ICU) and 74 deaths had been reported since the beginning of the pandemic.
- While the Pandemic (H1N1) 2009 has spread to all provinces and territories, approximately 90% of hospitalized cases and more than 85% of deaths are reported from 4 provinces (AB, MB, ON, QC). Hospitalized cases were reported from BC, AB, ON and NU this week.
- Children under 2 years of age, pregnant women, persons under 65 years of age with underlying medical conditions and Aboriginal populations have higher rates of hospitalizations and greater risk of severe outcomes (ICU admissions and deaths). Aboriginal communities have more pregnant women, young children, and underlying chronic disease than the general Canadian population, which may explain the disproportionate number of severe cases in this population.
Pandemic (H1N1) 2009 virus Surveillance and Epidemiology
The proportion of females affected, the median age and the proportion of cases with underlying medical conditions increases with severity of illness (see Characteristics table). Aboriginals were over-represented amongst those who were hospitalized, admitted to ICU and died. They account for 3% of the national population; however, 17% of hospitalizations, 14% of cases admitted to ICU and 10% of deaths were in this group. 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 have occurred in this group.
Those under one year of age have the highest hospitalization rate (33.8 per 100,000) followed by the children between 1 and 4 years of age (12.5 per 100,000) and between 5 and 14 years (7.3 per 100,000). Children under 5 years of age also have the highest ICU admission rate. In comparison, the highest mortality rate is occuring in those over 65 years of age (0.44 per 100,000), followed by the cases between 45 and 64 years (0.27 per 100,000).
Amongst all laboratory-confirmed hospitalized cases, 245 (17.0%) were Aboriginal (ie. First Nations, Inuit or Metis). Among 149 First Nations cases, 92 were from MB, 41 from QC, 11 from AB, 4 from BC and one from SK. The 66 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 (9), AB (2) and NWT (1). Metis cases (18) were from MB (13) and AB (5). Approximately 48% of the First Nations hospitalized cases are living on a reserve. Cases from Nunavut and those who were Inuit had higher hospitalization rates compared to First-Nations hospitalized cases (154.5 vs. 21.3 per 100,000) and higher mortality rates (4.0 vs 0.6 per 100,000). Because of small numbers reported, this should be interpreted with caution. However, hospitalized cases from Nunavut and of Inuit ethnicity were younger (median age 4 vs. 19), admitted to ICU less frequently (10.3% vs. 21.5%) and had fewer underlying medical conditions (19.2% vs. 63.1%) than those First Nations hospitalized cases.
Weekly and cumulative numbers
of hospitalizations and deaths among
Pandemic (H1N1) 2009 confirmed cases, Canada, to 5 September, 2009
| 1 One death occurred in a out-of-country resident in the province of Alberta. *The discrepancy in the total number of hospitalized cases from the province of Quebec is due to validation of the hospitalization status from the Regional Direction of Public Health. Numbers reported by any province or territory are subject to revision | ||||||
| This week | Cumulative | |||||
|---|---|---|---|---|---|---|
| Province/Territory | Hospitalized cases | ICU admissions | Deaths | Hospitalized cases | ICU-admitted cases | Deaths1 |
| BC | 2 | 0 | 0 | 44 | 18 | 4 |
| AB | 1 | 1 | 1 | 128 | 30 | 8 |
| SK | 0 | 0 | 0 | 23 | 12 | 4 |
| MB | 0 | 0 | 0 | 221 | 42 | 7 |
| ON | 4 | 1 | 0 | 365 | 64 | 23 |
| QC | 0* | 0 | 1 | 571 | 103 | 26 |
| 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 | 4 | 0 | 0 |
| NU | 4 | 0 | 0 | 66 | 6 | 1 |
| Canada | 11 | 2 | 2 | 1445 | 285 | 74 |
Descriptive characteristics of laboratory-confirmed Canadian Pandemic (H1N1) 2009 cases, hospitalized cases, cases admitted to ICU and deaths with core information available, reported to the Public Health Agency of Canada as of 29 August 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 aged between 15 and 44. |
||||
| Hospitalizated cases (n=1,445) | Cases admitted to ICU (n=285) | Deaths (n=74) | ||
|---|---|---|---|---|
| Females, % | 51.2 | 56.1 | 60.8 | |
| Median age | 23 | 37 | 51 | |
| Aboriginal status, % | 17.0 | 14.4 | 10.8 | |
| Underlying medical conditions1, % | 57.9 (584/1008) | 67.4 (151/224) | 76.4 (42/55) | |
| Pregnancy2, % | 28.7 (77/268) | 20.3 (15/74) | 30.8 (4/13) | |
Overall Influenza Summary - Week 35 (August 30 to September 5, 2009)
The overall influenza activity increased slightly this week relative to the previous week; two regions reported localized activity this week compared to none reported last week. One influenza outbreak was reported. The national ILI consultation rate and the proportion of postive tests remain stable compared to last week.
One region reported localized activity in NL, thirty-nine regions reported sporadic activity in BC, AB, SK, MB, ON, QC, NB, NS, PEI, NL, YT, NT & NU and 13 regions in AB, MB, QC, NB, NS & NL reported no activity. One region in ON did not report. One new influenza outbreak was reported in a hospital in NL this week.
Map of overall Influenza activity level
by provinces and territories, Week 35, Canada
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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.
Number of New Outbreaks in Long Term Care Facilities, Canada, by Report Week, 2009-2010
ILI consultation rate
This week, the national ILI consultation rate was 14 consultations per 1,000 patient visits (see ILI graph) which is slightly higher than expected for this time of year. The sentinel response rate was 71.8%.
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).
* Data arriving late may cause variations from results seen in previous weeks.
Paediatric Influenza Hospitalizations and deaths
In week 35, two laboratory-confirmed influenza-associated paediatric hospitalizations were reported through the Immunization Monitoring Program Active (IMPACT) network. The two hospitalizations this week were due to seasonal influenza A. 337 hospitalizations have been reported since week 17 (April 26); 99.4% of these hospitalizations have been due to Pandemic (H1N1) 2009. To date, 747 hospitalizations and five deaths have been reported this season. Three of the deaths were due to Pandemic (H1N1) 2009.
Laboratory Surveillance Summary
This week, the proportion of tests that were positive for influenza was 2.9% (see Tests table). The overall trend of the proportion of positive tests has been decreasing since the peak observed during week 23. A total of 119 specimen tested positive for influenza this week (all A). This week, 96.8% 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 & Cummulative 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 | 30 | 0 | 0 | 9 | 21 | 0 | 30 | 0 | 0 | 9 | 21 | 0 |
| AB | 46 | 0 | 0 | 8 | 38 | 0 | 46 | 0 | 0 | 8 | 38 | 0 |
| SK | 8 | 0 | 0 | 7 | 1 | 0 | 8 | 0 | 0 | 7 | 1 | 0 |
| MB | 2 | 0 | 0 | 1 | 1 | 0 | 2 | 0 | 0 | 1 | 1 | 0 |
| ON | 11 | 0 | 0 | 3 | 8 | 0 | 11 | 0 | 0 | 3 | 8 | 0 |
| QC | 19 | 0 | 0 | 0 | 19 | 0 | 19 | 0 | 0 | 0 | 19 | 0 |
| NB | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| NS | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| PE | 2 | 1 | 0 | 1 | 0 | 0 | 2 | 1 | 0 | 1 | 0 | 0 |
| NL | 1 | 0 | 0 | 1 | 0 | 0 | 1 | 0 | 0 | 1 | 0 | 0 |
| Canada | 119 | 1 | 0 | 30 | 88 | 0 | 119 | 1 | 0 | 30 | 88 | 0 |
Canadian situation *No update received from NML this week
Antigenic Characterization
NML has antigenically characterized 296 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
NML: All Pandemic (H1N1) 2009 viruses tested so far by NML have been sensitive to oseltamivir (527 samples) and zanamivir (280 samples) but resistant to amantadine (361 samples). However, one case of oseltamivir resistant Pandemic (H1N1) 2009 on July 21, 2009 was reported by the province of Quebec.
International update
Global information
- WHO: As of August 30, 2009, WHO reports 2,837 deaths with Pandemic (H1N1) 2009. Many countries in temperate regions of the southern hemisphere have passed the peak of their winter influenza epidemic. Sustained influenza activity continues to be reported in South Africa, Southern and Western parts of Australia, and in tropical regions. In the northern hemisphere, Japan reports continued increases in influenza activity, indicating an early beginning to the annual influenza season; China reports a surge in influenza cases; and the United States reports increased influenza activity in the Southeastern states. Pandemic (H1N1) 2009 is the predominant influenza strain worldwide.
- Antiviral resistance: 16 isolated cases of oseltamivir-resistant virus have been reported worldwide from different countries (Japan, USA, Hong Kong SAR, Denmark, Canada, Singapore and China).
- Zoonotic transmission: To date, 8 outbreaks of Pandemic (H1N1) 2009 have been identified in swine herds (Canada (2), Australia (3), Argentina (2), Indonesia (1)), and one in turkey flocks (Chile).
Southern Hemisphere
- Australia: As of September 8, 2009, Australia has 35,701 confirmed cases and 162 deaths. As of August 28, national influenza activity appears to be decreasing. The overall hospitalisation rate is 12.9 per 100,000 population with the highest rates in children aged less than 5 years of age. The median length of stay in hospital is 3 days (range 1-94 days). An increasing median age has been noted with the severity of disease: 21 years for all confirmed cases; 31 years for hospitalised cases; 43 years for ICU cases; and 54 years for cases who have died.
<http://www.healthemergency.gov.au/internet/healthemergency/publishing.nsf/Content/updates> and Content/ozflu2009.htm> - New Zealand: As of September 7, 2009, the total number of confirmed cases in New Zealand is 3,146 and 17 deaths. The number of ILI consultations continues to decrease, but is still higher than in previous years. The age standardised rate for cases is 75.1 per 100 000 total population. <http://www.moh.govt.nz/moh.nsf/indexmh/influenza-a-h1n1-news-media> <http://www.surv.esr.cri.nz/virology/influenza_weekly_update.php>
- Argentina: As of August 29, Argentina reports 8,384 confirmed cases of Pandemic (H1N1) 2009, a total of 8,962 cases of severe acute respiratory infection requiring hospitalization, and 512 Pandemic (H1N1)-associated deaths. The most affected age group for fatal cases is adults 50-59 years old. As of week 34, Pandemic (H1N1) 2009 and unsubtyped influenza A represented 92.7% of respiratory virus detections in patients >5 years old. In contrast, in children <5 years old, Pandemic (H1N1) and unsubtyped influenza A represents only 23.2% of detections, and RSV accounts for 70.4%.
<http://www.msal.gov.ar>
- Chile: As of September 1, the number of laboratory-confirmed cases in Chile is 12,190. In week 34, ILI activity was mild and decreased to 5.4 cases per 100,000 population. 1,504 confirmed cases have required hospitalization, representing a rate of 8.9 cases of acute infection per 100,000 population. The median age of severe cases is 33 years and 47% have underlying chronic disease. The rate of fatal cases is 0.8 per 100,000 population. Of 130 deaths, the median age was 49 years and 63.8% had underlying illness. Since EW 30, RSV is the predominant respiratory virus, and the proportion of RSV is 85.5% of respiratory virus detections in EW 34. <http://www.minsal.cl/>
- South Africa: As of September 8. South Africa reported a total of 7,606 laboratory-confirmed cases (1,735 new in the past week) and 31 deaths from Pandemic A(H1N1) 2009. In week 35, ending August 30, Pandemic (H1N1) 2009 and unsubtyped influenza A represent the majority of viral detections. South Africa represents 92.3% of the cases reported to WHO from the African Region.
<http://www.nicd.ac.za/>
<http://www.afro.who.int/ddc/influenzaa/index.html>
Northern Hemisphere
- United States: As of September 4, 2009, the CDC reports 9,079 hospitalized cases, and 593 deaths due to Pandemic (H1N1) 2009. From August 23-29, six states (Alabama, Alaska, Florida, Georgia, Mississippi, and South Carolina) and Puerto Rico are reporting widespread influenza activity. <http://www.cdc.gov/h1n1flu/update.htm> <http://www.cdc.gov/flu/weekly/>
- Mexico: As of September 8, 2009, Mexico reports 23,245 confirmed cases of Pandemic (H1N1), and 209 deaths. The majority (64.9%) of confirmed cases were in patients 5 to 29 years of age. However, the largest proportion of all deaths was observed in the older age groups, with 70.8% of all fatal cases in patients 20 to 54 years old. <http://portal.salud.gob.mx/>
- United Kingdom: As of September 3, 2009, pandemic influenza activity continues to decrease across most regions of the UK. GP consultation rates decreased in England and Northern Ireland but increased slightly in Wales and Scotland. HPA modelling gives an estimate of 4500 (range 2500 – 10,000) new cases in England in week 35. The cumulative number of deaths reported due to Pandemic (H1N1) 2009 in the UK is 70. <http://www.hpa.org.uk/webw>
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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