October 31 to November 6, 2010 (Week 44)
Summary of FluWatch Findings for the Week ending November 6, 2010
In week 44, five regions reported sporadic activity (BC, SK, ON & QC) and 45 regions reported no activity (See Activity level Map). No new influenza outbreak was reported during week 44. (Six regions did not report.)
Map of overall Influenza activity level by province and territory, Canada, Week 44
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.
† sub-regions within the province or territory as defined by the provincial/territorial epidemiologist. Graph may change as late returns come in.
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 44, the national ILI consultation rates was 11.7 consultations per 1,000 patients visits which was a return to the levels observed in the previous weeks and slightly below the expected levels for this time of year (see ILI graph). Adults between 20 and 64 years of age had the highest consultation rates (13.6 per 1,000 consultations) followed by those between 5 and 19 years of age (11.6 per 1,000).
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.
Laboratory Surveillance Summary
The proportion of tests that were positive for influenza during week 44 (1.23%, 22/1,784) has slightly increased compared to previous weeks. This proportion was higher than what was usually observed at this time of the year but much lower than during H1N1 2009 pandemic (see Tests table and Influenza tests graph). Of the 22 positive specimens, 12 specimens were reported as influenza A/H3N2 (BC, SK, ON & QC) and ten as unsubtyped influenza A (SK, ON & QC).During week 44, low levels of parainfluenza detections (3.1%), adenovirus (2.5%), respiratory syncytial virus (RSV) (2.0%) and human metapneumovirus (0.2%) continue to be reported (see Respiratory viruses graph). The proportion of specimens positive for rhinovirus has been high since the beginning of the influenza season (22.0% this week). Of the 65 positive influenza specimens for which we received detailed information, 52 were reported as A/H3N2, 10 as unsubtyped, two as pandemic H1N1 2009 and one influenza type B. 70% (7/10) of cases with A/H3N2 reported with detailed information were aged below 45 years. However, since August 29, 2010, 50% (26/52) of positive specimens for influenza A/H3N2 reported through the case-based laboratory reporting were aged over 65 years (see Tests detailed table).
*Unsubtyped: The specimen was typed as influenza A, but no test for subtyping was performed. 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.
|Reporting provinces||Weekly (October 31 to November 6, 2010)||Cumulative (August 29, 2010 to November 6, 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|
* Please note that this table reflects the number of specimens for which demographic information was reported. These represent a subset of all positive influenza cases reported. Four provinces have reported detailed case-by-case data since the beginning of the season (BC, AB, MB and ON). Delays in the reporting of data may cause data to change retrospectively.
(October 31 to November 6, 2010) (10/22)
(August 29, 2010 to November 6, 2010) (65/107)
|Influenza A||B||Influenza A||B|
|A Total||Pandemic H1N1||A/H3N2||A unsubtyped||Total||A Total||Pandemic H1N1||A/H3N2||A unsubtyped||Total|
Paediatric Influenza Hospitalizations and Deaths
In week 44, one laboratory-confirmed influenza-associated paediatric (18 years of age and under) hospitalization was reported through the Immunization Monitoring Program Active (IMPACT) network. The case aged between 6 and 23 months was from ON and was due to influenza A/H3N2. Since the beginning of the season, two hospitalizations were reported among children aged under 2 years and were all due to influenza A/H3N2.
Adult Influenza Hospitalizations and Deaths
During week 44, no new laboratory-confirmed influenza-associated adult (16 years of age and older) hospitalizations were reported through the Canadian Nosocomial Infection Surveillance Program (CNISP) from 35 sites. Since the beginning of the season, 11 hospitalized cases have been reported (2 A/H3N2, 1 pandemic H1N1 and 8 influenza A unsubtyped from BC, ON and QC). Eight of the 11 cases were aged over 65 years and seven out of 11 were males.
Sale of antivirals (AV)
During week 44,antiviral prescriptions monitoring results demonstrated a plateau in antiviral prescription rates at the national level and among the provinces and territories, although daily and weekly antiviral data at the Health Region level showed low antiviral prescription rates compared to this time last year.
Since September 1, 2010, National Microbiology Laboratory (NML) has antigenically characterized 20 influenza viruses (17 A/H3N2 from BC, AB, MB, ON & QC, 1 pandemic H1N1 2009 in ON and 2 B virus from QC and BC) that were received from provincial laboratories. The 17 influenza A/H3N2 viruses characterized were related to A/Perth/6/2009, which is the influenza A/H3N2 component recommended for the 2010-11 influenza vaccine. The pandemic H1N1 2009 characterized was antigenically related to the pandemic vaccine virus A/California/7/2009, which is the recommended H1N1 component for the 2010-11 Northern Hemisphere influenza vaccine. The influenza B virus characterized was antigenically related to B/Brisbane/60/08 (Victoria lineage), which is the recommended influenza B component for the 2010-11 influenza vaccine.
Since the beginning of the 2010-2011 season, no oseltamivir resistant pandemic H1N1 2009 have been reported. So far this season, the NML has tested 17 influenza A/H3N2 and one pandemic H1N1 isolates for amantadine resistance and found that all isolates were resistant to amantadine. 15 influenza isolates (13 A/H3N2, 1 pandemic H1N1 and 1 B) were also tested for oseltamivir and zanamivir resistance and found that all isolates were sensitive to both antivirals.
WHO: Worldwide, overall influenza activity remained low, except in parts of the tropics, most notably in Southeast Asia, and to a lesser extent in the tropical areas of the Americas. After late winter and springtime influenza epidemics in several countries of the temperate Southern Hemisphere, influenza activity has returned to near or below baseline in most places. However, a recent post-season rise in cases has been noted across parts of southern Africa associated with localized outbreaks of pandemic H1N1 2009. Seasonal influenza A/H3N2 viruses continued to be the predominant circulating strain of influenza viruses worldwide, however, in many countries there has been co-circulation of seasonal influenza B viruses and to a lesser extent, pandemic H1N1 2009. The latter has been recently predominant in a limited
number of countries, including in India.
United States: During week 44, influenza activity remained low in the United States. The geographic spread of influenza in the U.S. Virgin Islands was assessed as regional; Guam and one state reported local influenza activity; the District of Columbia, Porto Rico and 28 states were assessed as sporadic; and 21 states reported no influenza activity. 25 (1.4%) specimens were tested positive for influenza this week. The proportion of outpatient visits for influenza-like illness (ILI) and the proportion of deaths attributed to pneumonia and influenza (P&I) were both below the national baseline. One influenza-associated pediatric death was reported. This death was associated with an influenza A virus for which the subtype was undetermined and occurred during the 2009-10 season. <http://www.cdc.gov/flu/weekly/index.htm>
Latin America: In the tropics of the Americas, between late July and early October, many countries or parts of countries experienced periods of active circulation of influenza viruses, including but not limited to southern Mexico, Costa Rica, Nicaragua, El Salvador, Honduras, Jamaica, Cuba, Peru, Colombia, and Bolivia. In most of these countries, seasonal influenza A/H3N2 was the predominant circulating influenza virus. Notably, Nicaragua observed circulation of predominantly influenza B viruses, while Colombia and Bolivia experienced circulation of predominantly pandemic H1N1 2009. In most countries of the region, overall influenza virus transmission has declined substantially or returned to very low levels. <http://www.who.int/csr/disease/influenza/2010_11_08_GIP_surveillance/en/index.html>
Europe: Rare detections of influenza virus along with sporadic detections of respiratory syncytial virus in a number of European countries suggested that the low influenza-like illness and acute respiratory infection activity currently observed was likely due to respiratory pathogens other than influenza. The large majority of countries continued to report low rates and unchanging trends in sentinel physician consultations for influenza-like illness and acute respiratory infection. During week 43, nine (2.6%) of 344 sentinel specimens tested positive for influenza virus. Sixteen of 18 influenza viruses detected in sentinel and non-sentinel specimens were type A, and the other two were type B. Of the 10 subtyped, eight were pandemic H1N1 2009 and two were A/H3N2. One SARI case considered to be related to flu was reported during week 43.
Asia: In the tropics of Asia, the most active reported circulation of influenza viruses continued to be in Thailand. Since late July 2010, pandemic H1N1 2009 has been the predominant circulating influenza viruses in Thailand, however, more recently beginning in early October 2010, seasonal influenza A/H3N2, B, and pandemic H1N1 2009 viruses began to co-circulate at similar levels. In southern China and Hong Kong (SAR), recent periods of active circulation of seasonal influenza A/H3N2 viruses during late summer and autumn appeared to have largely subsided. In India, the national epidemic of pandemic H1N1 2009 which began during June 2010 and lasted until late September 2010 has largely subsided but small numbers of new cases continued to reported weekly. In Bangladesh, there has been persistent influenza virus transmission since the early part of 2010, however; only in recent months has circulation of seasonal influenza A/H3N2 become predominant.
South America: In Chile, an unusually late winter and springtime influenza epidemic, characterized by predominance of circulating seasonal influenza A/H3N2 viruses, and to a lesser extent seasonal influenza B and pandemic H1N1 2009, appears to have largely subsided. A similarly timed influenza epidemic was also observed in Paraguay and Uruguay. In Argentina, however, little winter and springtime influenza activity was observed during 2010, with influenza B viruses accounting for the majority of sporadic influenza virus detections.
FluWatch reports include data and information from the following sources: laboratory reports of positive influenza tests in Canada (National Microbiology Laboratory), sentinel physician reporting of influenza-like illness (ILI), provincial/territorial assessment of influenza activity based on various indicators, including laboratory surveillance, ILI reporting, and outbreaks, influenza-associated paediatric and adult hospitalizations, antiviral sales in Canada, and WHO and other international reports of influenza activity.
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 2010-2011 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 2010-2011 season:
Schools: Greater than 10% absenteeism (or absenteeism that is higher (e.g. >5-10%) than expected level as determined by school or public health authority) which is likely due to ILI. Note: it is recommended that ILI school outbreaks be laboratory confirmed at the beginning of influenza season as it may be the first indication of community transmission in an area.
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) and prisons.
Other settings: 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 Definition for the 2010-2011 season
Influenza Activity levels are defined as:
1 = No activity: no laboratory-confirmed influenza detections in the reporting week, however, sporadically occurring ILI may be reported
2 = Sporadic: sporadically occurring ILI and lab confirmed influenza detection(s) with no outbreaks detected within the influenza surveillance region†
3 = Localized:
4 = Widespread:
Note: ILI data may be reported through sentinel physicians, emergency room visits or health line telephone calls.
* More than just sporadic as determined by the provincial/territorial epidemiologist.
† Influenza surveillance 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) 998-8862.