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October 4, 2009 to October 10, 2009 (Week 40) |
Fluwatch
Summary of FluWatch Findings for the
Week ending October 10, 2009
- The overall influenza activity has increased for a fourth consecutive week. The national ILI consultation rate and the proportion of positive tests for influenza were quite high compared to the previous weeks. The total number of influenza outbreaks was lower than last week but still high for this time of the year with 28 influenza outbreaks.
- BC had particularly high influenza activity this week with more than 30% of positive influenza tests and 17 influenza outbreaks. NT was also affected with their two regions reporting widespread activity and 8 outbreaks.
- This week, approximatively 97% of the positive influenza A subtyped specimens were Pandemic (H1N1) 2009, and the remainder were seasonal A (H1N1).
- The intensity of Pandemic (H1N1) 2009 in the population was moderate with thirty-seven hospitalizations and two deaths reported this week. Hospitalized cases were reported from BC, AB, ON, QC and NT while the deaths were from BC and ON. As of October 10, 2009, a total of 1,541 hospitalized cases including 299 cases admitted to an intensive care unit (ICU) and 158 cases required ventilation as well as 80 deaths had been reported since the beginning of the pandemic.
- A third case of oseltamivir resistant Pandemic (H1N1) 2009 case was reported this week from the province of Ontario.
- The influenza activity remained elevated in the U.S. for a sixth consecutive week.
Pandemic (H1N1) 2009 virus Surveillance and Epidemiology
A total of 1,541 hospitalized cases including 299 (19.4%) cases admitted to ICU and 158 (10.3%) cases required ventilation as well as 80 deaths of Pandemic (H1N1) 2009 were reported to PHAC as of October 10, 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. While they account for 3% of the national population, 18% of hospitalizations, 16% of cases admitted to ICU and 13% of deaths were reported 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 4.6 per 100,000 population with the highest rates in children under 15 years of age (10.9 per 100,000). The national mortality rate was 0.24 per 100,000 population; those 45 years and older had the highest mortality rate (0.35 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, 279 (18.1%) were Aboriginal (173 First Nations, 82 Inuit, 19 Metis and 5 unknown ethnicity). Approximately 45% of the hospitalized cases among those reported as First Nations were living on a reserve. Cases among all Inuit including those from Nunavut had higher hospitalization rates compared to the First Nations population (162.4 vs. 24.8 per 100,000) and higher mortality rates (4.0 vs 0.9 per 100,000) (caution: rate based on small fatality numbers). 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 (11.0% vs. 20.2%), required ventilation less frequently (3.7% vs. 17.9%) and had fewer underlying medical conditions (31.3% vs. 63.5%) compared to First Nations hospitalized cases.
Weekly and cumulative numbers
of hospitalizations, ICU admissions and deaths among
Pandemic (H1N1) 2009 confirmed cases, Canada, to 10 October, 2009
| Province/Territory | This week (Oct. 4-10, 2009) | Cumulative | ||||
|---|---|---|---|---|---|---|
| Hospitalized cases | ICU admissions | Deaths | Hospitalized cases | ICU-admitted cases | Deaths | |
| BC | 14 | 2 | 1 | 78 | 24 | 7 |
| AB | 2 | 0 | 0 | 133 | 31 | 8 |
| SK | 0 | 0 | 0 | 24 | 12 | 4 |
| MB | 0 | 0 | 0 | 226 | 43 | 7 |
| ON | 7 | 0 | 1 | 387 | 66 | 25 |
| QC | 6 | 1 | 0 | 586 | 105 | 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 | 8 | 1 | 0 | 18 | 2 | 0 |
| NU | 0 | 0 | 0 | 66 | 6 | 1 |
| Canada | 37 | 4 | 2 | 1541 | 299 | 80 |
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 10 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=1,541) | Cases admitted to ICU (n=299) | Deaths (n=80) | ||
|---|---|---|---|---|
| Females, % | 51.6 | 56.9 | 61.3 | |
| Median age | 23 | 37 | 50 | |
| Aboriginal status, % | 18.1 | 15.7 | 12.5 | |
| Underlying medical conditions1, % | 61.3 (621/1,013) | 71.6 (159/222) | 80.3(49/61) | |
| Pregnancy2, % | 27.6 (81/293) | 18.8 (15/80) | 28.6 (4/14) | |
Overall Influenza Summary - Week 40 (October 4 to October 10, 2009)
The overall influenza activity has increased for a fourth consecutive week. The national ILI consultation rate and the proportion of positive tests for influenza were quite high compared to the previous weeks. The total number of influenza outbreaks was lower than last week but still high for this time of the year with 28 influenza outbreaks.
Four regions reported widespread activity in BC & NT and five regions in BC & ON reported localized activity, while thirty regions reported sporadic activity in BC, AB, SK, MB, ON, QC, NB, PEI, NS, NL, YK & NU and fifteen regions in SK, MB, QC, NB, NS & NL reported no activity. The twenty-eight influenza outbreaks reported this week were all in schools except one in a Long-term care facility in Ontario. The schools outbreaks were in BC (17), NT (8), AB (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) 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 40, 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.
Overall Number of Influenza Outbreaks, Canada, by Report Week, 2009-2010
ILI consultation rate
This week, the national ILI consultation rate was 43 consultations per 1,000 patient visits (see ILI graph) which is higher compared to the previous weeks and still above the expected range for this time of the year. The sentinel response rate was 94.4%. Five provinces (MB, ON, NS, 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 79.4 and 91.8 per 1,000 patient visits among children under 4 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 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 40, two laboratory-confirmed influenza-associated paediatric hospitalizations were reported through the Immunization Monitoring Program Active (IMPACT) network. One hospitalization reported this week was due to seasonal influenza A and one was due to Pandemic (H1N1) 2009. 379* hospitalizations had been reported since week 17 (April 26); 93.7% 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.
*Please note that changes in the total number of hospitalizations may have occurred due to updated case information.
Laboratory Surveillance Summary
This week, the proportion of tests that were positive for influenza was 8.7% which is a significant increase compared to the previous weeks (see Tests table). The Prairies, Ontario and Quebec had a high proportion of positive tests for influenza this week of approximatively 5%, while British Columbia had over 30% of positive tests for influenza. A total of 593 specimens tested positive for influenza this week (all A except 1 B). 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 |
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| Reporting provinces | Weekly (Oct. 4-10, 2009) | 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 | 346 | 0 | 0 | 12 | 334 | 0 | 804 | 0 | 0 | 304 | 500 | 0 |
| AB | 135 | 0 | 0 | 41 | 94 | 0 | 317 | 0 | 0 | 83 | 234 | 0 |
| SK | 8 | 0 | 0 | 5 | 3 | 0 | 28 | 0 | 0 | 24 | 4 | 0 |
| MB | 3 | 0 | 0 | 3 | 0 | 0 | 7 | 0 | 0 | 4 | 3 | 0 |
| ON | 75 | 3 | 0 | 28 | 44 | 0 | 164 | 4 | 0 | 55 | 105 | 0 |
| QC | 21 | 0 | 0 | 0 | 21 | 0 | 67 | 0 | 0 | 0 | 67 | 0 |
| NB | 0 | 0 | 0 | 0 | 0 | 1 | 5 | 0 | 1 | 2 | 2 | 1 |
| NS | 5 | 0 | 0 | 4 | 1 | 0 | 16 | 0 | 0 | 11 | 5 | 0 |
| PE | 0 | 0 | 0 | 0 | 0 | 0 | 2 | 0 | 0 | 2 | 0 | 0 |
| NL | 0 | 0 | 0 | 0 | 0 | 0 | 2 | 0 | 0 | 2 | 0 | 0 |
| Canada | 593 | 3 | 0 | 93 | 497 | 1 | 1412 | 4 | 1 | 487 | 920 | 1 |
Sale of antivirals (AV) in Canada
In week 40, compared to other prescriptions filled in Canada, the sale of AV suggested continued increases in most provinces/territories. The most pronounced increases were among children (aged between 2 and 17 years of age) and in the province of British Columbia.
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 nine influenza A viruses that were received from Canadian Laboratories. The nine 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.
Antiviral Resistance
NML: The nine 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 and resistant to amantadine.
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.
International update
Global information
- WHO: As of 11 October 2009, WHO reported more than 399,232 laboratory confirmed cases of Pandemic (H1N1) 2009 with more than 4,735 deaths. Influenza activity continues to increase in the northern temperate zones across the world. In North America, the United States is now experiencing nationwide rates of Influenza-Like Illness (ILI) well above seasonal baseline rates with high rates of pandemic H1N1 2009 virus detections in clinical laboratory specimens. Mexico also reports high intensity and active transmission in some areas of the country. Western Europe and northern Asia are experiencing increased rates of ILI, well above baseline in some countries but activity is generally not as widespread as in North America. Of note, nearly half of the influenza viruses detected in China are seasonal influenza A (H3N2) viruses, which appeared prior to and is co-circulating with Pandemic (H1N1) 2009 virus.The tropical zones continue to have transmission that is mixed as some countries have now peaked and are declining, while others are experiencing increases. In the tropical region of the Americas, several Caribbean Island nations are now reporting increased rates of illness while Brazil, Costa Rica and other countries on the continent are declining. In South Asia, most countries now report a decline in rates of illness. Influenza rates in the temperate zones of the Southern Hemisphere have all returned to below baseline levels and very few detections of pandemic H1N1 2009 virus are being reported.
<http://www.who.int/csr/don/2009_10_09/en/index.html>
Northern Hemisphere
- United States: During week 39 (27 September to 3 October, 2009), influenza activity increased in the U.S with 99% of all sub-typed influenza A viruses being Pandemic (H1N1) 2009 viruses. The proportion of outpatient visits for influenza-like illness (ILI) was above the national baseline. Thirty-seven states reported geographically widespread influenza activity. For this week, 19 influenza-associated pediatric deaths were reported with 16 of these deaths associated with Pandemic (H1N1) 2009 and three were associated with influenza A virus, for which subtype is unknown. Since 28 September 2008, total pediatric deaths reported are 147 with seventy-six of these deaths occurring due to Pandemic (H1N1) 2009 virus infections. Twenty-nine of these deaths have occurred since 30 August 2009. For week 39, the proportion of deaths attributed to pneumonia and influenza was at the epidemic threshold.
<http://www.cdc.gov/flu/weekly/> - Mexico: Daily diagnoses reached higher levels in September than the Pandemic (H1N1) 2009 peak in April, with 659 new cases in just one day this month alone. As of October 12, 2009, Mexico reported 39,489 confirmed cases of Pandemic (H1N1) 2009, and 255 deaths. The majority of deaths (69.0%) occurred between the ages of 20 and 54 with male and female cases representing 51% and 49% respectively.
<http://portal.salud.gob.mx/contenidos/noticias/influenza/estadisticas.html> - United Kingdom: As of 8 October 2009, pandemic influenza activity is variable across the UK with the main burden of disease being in school-aged children and young adults. Health Protection Agency modelling gave an estimate of 18,000 (range 9000 – 38,000) new cases in England in week 40. 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 89. The highest hospitalisation rates have consistently been in the under 5-year age group, though rates have been constant in all age groups. Since the beginning of autumn term, a minimum of 58 schools throughout England have reported outbreaks of ILI. School outbreaks have also been reported from Scotland, Wales and Northern Ireland.
<http://www.hpa.org.uk/web/HPAwebFile/HPAweb_C/1254510391851> - France: For week 41 (from 5 to11 October 2009), the Pandemic (H1N1) 2009 virus continues to circulate and the use of medical care for flu and acute respiratory infections remains high but stable. During this week, the ILI consultation rate remained stable (189 cases per 100,000 which is above the epidemic threshold of 108 cases per 100,000). Excess weekly ILI consultations are estimated at 94,000 however a third of these are related to Pandemic (H1N1) 2009. The number of hospitalized cases is still low but rising. Four new cases of severe Pandemic (H1N1) 2009 were reported however there were no new deaths. Total deaths in France related to Pandemic (H1N1) 2009 reported is 32.
<http://www.invs.sante.fr/display/?doc=surveillance/grippe_dossier/points_h1n1/grippe_A_h1n1_131009/index.html> - Spain: As of 8 October 2009, the estimated rate of clinical influenza in primary care (27 September to 3 October) was 94.7 per 100,000. In the past week, the number of clinical influenza cases increased by approximately 42,327 of which 95.8% were positive for Pandemic (H1N1) 2009. Almost all cases presented with mild symptoms. To date, the cumulative number of deaths reported due to Pandemic (H1N1) 2009 in Spain is 43.
<http://www.msps.es/en/servCiudadanos/alertas/informesGripeA/091008.htm>
Southern Hemisphere
- Australia: As of 13 October 2009, Australia has reported a total of 36,910 confirmed cases of pandemic (H1N1) 2009. New hospitalizations are now being reported instead of current hospitalizations as the country has moved from daily to weekly reporting. In the past week there have been 24 new hospitalizations of pandemic (H1N1) 2009 and of these, 2 were admitted to ICU. Total hospitalizations reported for Australia is 4,830. The number of deaths associated with pandemic (H1N1) 2009 continues to increase with a total of 185 being reported. Of these, four were pregnant women and 24 were Indigenous.
<http://www.healthemergency.gov.au/internet/healthemergency/publishing.nsf/
Content/2A7A47BEE38EF906CA25764D000DE16F/$File/131009.pdf> - New Zealand: As of 14 October 2009, the total number of confirmed cases in New Zealand is 3175, which is only one additional case from last week. The rate of infection is continuing to decrease however influenza activity levels remain active. During this week, there has only been one person hospitalized, a decrease from four last week. There are no new reported deaths. 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-update-155-141009>
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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