November 7 to November 13, 2010 (Week 45)

Posted 2010-11-19

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Overall Influenza Summary – Week 45 (November 7 to November 13, 2010)

In week 45, while one region reported localized activity (ON), nine regions reported sporadic activity (BC, SK, ON & QC) and 46 regions presented no activity (See Activity level Map). One new influenza outbreak was reported in a long-term care facility during week 45 in ON.

Map of overall Influenza activity level by province and territory, Canada, Week 45
	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.

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Number of influenza surveillance regions^† reporting widespread or localized influenza activity, Canada, by report week, 2010-2011 (N=56)

† sub-regions within the province or territory as defined by the provincial/territorial epidemiologist. Graph may change as late returns come in.

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Overall Number of Influenza Outbreaks, Canada, by Report Week, 2010-2011

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.

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ILI consultation rate

During week 45, the national ILI consultation rates was 17.4 consultations per 1,000 patients visits which was similar to what was observed in the previous weeks and within the expected levels for this time of year (see ILI graph). Children under 5 years of age had the highest consultation rates (47.1 per 1,000 consultations) followed by those between 5 and 19 years of age (44.0 per 1,000).

Influenza-like illness (ILI) consultation rates, Canada, by report week, 2010-2011 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 retrospectively.

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Laboratory Surveillance Summary

The proportion of tests that were positive for influenza during week 45 (2.15%, 42/1,951) has 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 42 positive specimens, 15 specimens were reported as influenza A/H3N2 (ON & QC), 23 as unsubtyped influenza A (ON & QC) and four as influenza B (BC, ON & QC).Since the beginning of the season, 97% of the subtyped positive influenza specimens were for influenza A/H3N2. During week 45, low levels of parainfluenza detections (2.8%), adenovirus (2.7%), respiratory syncytial virus (RSV) (2.5%) and human metapneumovirus (0.1%) 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 (16% this week). This week, 100% (6/6) of cases with A/H3N2 reported through the detailed case-based laboratory reporting were aged over 65 years, while since August 29, 2010, the proportion was 55% (35/64) (see Tests detailed table).

Weekly & Cumulative numbers of positive influenza specimens by Provincial Laboratories, Canada, 2010-2011

*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 (November 7 to November 13, 2010)						Cumulative (August 29, 2010 to November 13, 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
BC	0	0	0	0	0	1	12	0	8	0	4	2
AB	0	0	0	0	0	0	11	0	11	0	0	0
SK	0	0	0	0	0	0	2	0	1	0	1	0
MB	0	0	0	0	0	0	1	0	1	0	0	0
ON	20	0	8	0	12	1	84	0	24	2	58	1
QC	18	0	7	0	11	2	32	0	12	0	20	4
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	0	0	0	0	0	0	0	0	0	0	0	0
NL	0	0	0	0	0	0	0	0	0	0	0	0
Canada	38	0	15	0	23	4	142	0	57	2	83	7

Weekly & Cumulative numbers of positive influenza specimens by age groups reported through case-based laboratory reporting, Canada, 2010-2011*

* 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. Five provinces have reported detailed case-by-case data since the beginning of the season (BC, AB, SK, MB and ON). Delays in the reporting of data may cause data to change retrospectively.
Age groups	Weekly (November 7 to November 13, 2010) (9/42)					Cumulative (August 29, 2010 to November 13, 2010) (80/149)
	Influenza A				B	Influenza A				B
	A Total	Pandemic H1N1	A/H3N2	A unsubtyped	Total	A Total	Pandemic H1N1	A/H3N2	A unsubtyped	Total
<5	0	0	0	0	0	9	0	8	1	0
5-19	0	0	0	0	0	6	0	6	0	0
20-44	0	0	0	0	0	11	0	10	1	1
45-64	0	0	0	0	2	7	2	5	0	2
65+	7	0	6	1	0	43	0	35	8	0
Unknown	0	0	0	0	0	1	0	0	1	0
Total	7	0	6	1	2	77	2	64	11	3

Influenza tests reported and percentage of tests positive, Canada, by report week, 2010-2011

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Percent positive influenza tests, compared to other respiratory viruses, Canada, by reporting week, 2010-2011

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Canadian situation

Paediatric Influenza Hospitalizations and Deaths
In week 45, 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 2 and 4 years was from BC and was due to influenza A/H3N2. Since the beginning of the season, three hospitalizations were reported among children aged under 4 years and were all due to influenza A/H3N2.

Adult Influenza Hospitalizations and Deaths
During week 45, two new laboratory-confirmed influenza-associated adult (16 years of age and older) hospitalizations were reported through the Canadian Nosocomial Infection Surveillance Program (CNISP) from 26 sites. Both were male patients; one aged aged between 45 and 64 years with unsubytped influenza A and one over 80 years of age with influenza A/H3N2. Since the beginning of the season, 13 hospitalized cases have been reported (3 A/H3N2, 1 pandemic H1N1 and 9 influenza A unsubtyped from BC, ON and QC). 9 of the 13 (69%) cases were aged over 65 years and were males.

Sale of antivirals (AV)
During week 45, 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.

Antigenic Characterization
Since September 1, 2010, National Microbiology Laboratory (NML) has antigenically characterized 24 influenza viruses (21 A/H3N2 from BC, AB, MB, ON & QC, 1 pandemic H1N1 2009 in ON and 2 B viruses from BC and QC) that were received from provincial laboratories. The 21 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 two influenza B viruses characterized was antigenically related to B/Brisbane/60/08 (Victoria lineage), which is the recommended influenza B component for the 2010-11 influenza vaccine.

Antiviral Resistance 
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 22 influenza A/H3N2 and one pandemic H1N1 isolates for amantadine resistance and found that all isolates were resistant to amantadine. 22 influenza isolates (19 A/H3N2, 1 pandemic H1N1 and 2 B) were also tested for oseltamivir and zanamivir resistance and found that all isolates were sensitive to both antivirals.

International influenza update

Global information

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.
<http://www.who.int/csr/disease/influenza/2010_11_08_GIP_surveillance/en/index.html>

Geographic update

Northern hemisphere

United States: During week 44, influenza activity remained low in the United States. The geographic spread of influenza in three states was reported as local; the District of Columbia, Puerto Rico and 34 states was assessed as sporadic; Guam and 13 states reported no influenza activity and the US Virgin Islands did not report. 185 (6.8%) specimens were tested positive for influenza this week. Two human infections with novel influenza A viruses were reported. 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 and was associated with an influenza A virus for which the subtype was undetermined.
<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. Epidemiological indicators showed no or only sporadic influenza activity in 24 of the 25 reporting EU countries.
Malta reported local spread and Bulgaria reported medium intensity of acute respiratory infection. During week 44, 15 (4.9%) of 309 sentinel specimens tested positive for influenza virus. 27 of 41 influenza viruses detected in sentinel and non-sentinel specimens were type A, and 14 were type B. Of the 16 subtyped influenza A viruses, 15 were pandemic H1N1 2009 and one was A/H3N2. Three SARI cases, not related to influenza were reported during week 44.
<http://ecdc.europa.eu/en/publications/Publications/101119_SUR_Weekly_Influenza_Surveillance_Overview.pdf>

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.
<http://www.who.int/csr/disease/influenza/2010_11_08_GIP_surveillance/en/index.html>

Southern hemisphere

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.
<http://www.who.int/csr/disease/influenza/2010_11_08_GIP_surveillance/en/index.html>

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