Fluwatch Report: October 28 to November 3, 2012 (Week 44)

Influenza Activity (geographic spread) and Outbreaks

In week 44, 5 regions [within AB(1), SK(1), ON(2) and QC(1)] reported localized activity, 9 regions [within BC(1), AB(2), MB(1), ON(1), QC(3) and PE(1)] reported sporadic activity and the rest reported no activity (Figures 1 and 2). Six new influenza outbreaks were reported in week 44 [in AB(2), SK(1), ON(2) and QC(1)] and all were in long-term care facilities (Figure 3).

Figure 1. 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.

Text equivalent for figure 1Map of overall Influenza activity level by province and territory, Canada

Figure 2. Number of influenza surveillance regions^† reporting widespread or localized influenza activity, Canada, by report week, 2012-2013 (N^*=58)

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

* Total number of influenza surveillance regions in Canada

Text equivalent for figure 2Number of influenza surveillance regions reporting widespread or localized influenza activity, Canada, by report week, 2011-2012 (N=56)

Figure 3. Overall Number of Influenza Outbreaks, Canada, by Report Week, 2012-2013

Text equivalent for figure 3Overall Number of Influenza Outbreaks, Canada, by Report Week, 2011-2012

Influenza and Other Respiratory Virus Detections

The percentage of positive influenza tests increased from the previous week, from 1.3% in week 43 to 2.8% in week 44 (Figures 4 and 5). Among the influenza viruses detected this week (n=64), 90.6% were positive for influenza A viruses [of which 70.7% were A(H3) and 29.3% were A unsubtyped] and 9.4% for influenza B viruses (Table 1).

Cumulative influenza virus detections by type/subtype to date are as follows: 91.6% influenza A [64.5% A(H3), 4.6% A(H1N1)pdm09 and 30.9% A(unsubtyped)] and 8.4% influenza B (Table 1).

Detailed information on age and type/subtype was received for 104 cases to date this season (Table 2).The proportions of cases by age group were as follows: 8.7% were < 5 years; 8.7% were between 5-19 years; 13.5% were between 20-44 years; 15.4% were between 45-64 years of age; 53.9% were ≥ 65 years.

The percentage positive for rhinovirus detections decreased from the previous week, from 20.6% in week 43 to 15.5% week 44; but remains the highest compared to the other respiratory viruses. The percentage positive for the other respiratory viruses in week 44 remained low, although RSV and parainfluenza increased slightly compared to week 43: RSV 2.4%; parainfluenza 3.3%; adenovirus 1.1%; hMPV 0.2%; and coronavirus 1.3% (Figure 5). For more details, see the weekly Respiratory Virus Detections in Canada Report.

Table 1: Weekly & Cumulative numbers of positive influenza specimens
by Provincial Laboratories, Canada, 2012-2013

Reporting provinces	Weekly (October 28 to November 3, 2012)						Cumulative (August 26, 2012 to November 3, 2012)
	Influenza A					Influenza B	Influenza A					Influenza B
	A Total	A(H1)	A(H3)	Pand H1N1	A ( Un S)Table 1 note*	Total	A Total	A(H1)	A(H3)	Pand H1N1	A (Un S) Table 1 note*	Total
* 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: Weekly data is based on week of positive lab detection. Cumulative data includes updates to previous weeks; due to reporting delays, the sum of weekly report totals do not add up to cumulative totals.
BC	1	0	0	0	1	2	7	0	4	0	3	3
AB	28	0	24	0	4	0	60	0	44	7	9	2
SK	1	0	0	0	1	0	3	0	0	0	3	1
MB	1	0	0	0	1	0	4	0	3	0	1	0
ON	17	0	12	0	5	1	59	0	39	0	20	3
QC	9	0	4	0	5	3	16	0	5	0	11	5
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	1	0	1	0	0	0	1	0	1	0	0	0
NL	0	0	0	0	0	0	2	0	2	0	0	0
Canada	58	0	41	0	17	6	152	0	98	7	47	14

Table 2. Weekly & Cumulative numbers of positive influenza specimens by age groups
reported through case-based laboratory reporting, Canada, 2012-2013 Table 2 note*

Age groups	Weekly (October 28 to November 3, 2012)					Cumulative (August 26, 2012 to November 3, 2012)
	Influenza A				B	Influenza A				B
	A Total	Pandemic H1N1	A/H3N2	A unsubtyped	Total	A Total	Pandemic H1N1	A/H3N2	A unsubtyped	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. Delays in the reporting of data may cause data to change retrospectively.
< 5	0	0	0	0	0	7	1	6	0	2
5-19	4	0	2	2	0	9	0	6	3	0
20-44	2	0	2	0	0	13	3	6	4	1
45-64	3	0	2	1	0	13	1	6	6	3
65+	16	0	15	1	0	55	2	37	16	1
Unknown	0	0	0	0	0	0	0	0	0	0
Total	25	0	21	4	0	97	7	61	29	7

Figure 4. Influenza tests reported and percentage of tests positive, Canada,
by report week, 2012-2013

Text equivalent for figure 4Influenza tests reported and percentage of tests positive, Canada, by report week, 2011-2012

Figure 5. Percent positive influenza tests, compared to other respiratory viruses,
Canada, by reporting week, 2012-2013

Text equivalent for figure 5Percent positive influenza tests, compared to other respiratory viruses, Canada, by reporting week, 2011-2012

Influenza strain characterizations

Since the start of the season, the National Microbiology Laboratory (NML) has antigenically characterized 6 influenza viruses [4 A(H3N2) and 2 B]. The 4 influenza A(H3N2) viruses (from BC and ON) were antigenically similar to the vaccine strain A/Victoria/361/2011. Both of the influenza B viruses (from ON and QC) were antigenically similar to the vaccine strain B/Wisconsin/01/2010 (Yamagata lineage) (Figure 6).

Figure 6. Influenza strain characterizations, Canada, 2012-2013, N = 6

Note:The recommended components for the 2012-2013 Northern Hemisphere influenza vaccine include: an A/Victoria/361/2011 (H3N2)-like virus; an A/California/7/2009 (H1N1)pdm09-like virus; and a B/Wisconsin/1/2010-like virus.

Text equivalent for figure 6Influenza strain characterizations, Canada, 2011-2012

Antiviral resistance

Since the beginning of the season, NML has tested 6 influenza viruses [4 A(H3N2) and 2 B] for resistance to oseltamivir and zanamivir and it was found that all were sensitive to oseltamivir and zanamivir. A total of 14 influenza A(H3N2) viruses were tested for amantadine resistance and all were resistant (Table 3).

Table 3. Antiviral resistance by influenza virus type and subtype, Canada, 2012-2013

Virus type and subtype	Oseltamivir		Zanamivir		Amantadine
	# tested	# resistant (%)	# tested	# resistant (%)	# tested	# resistant (%)
* NA - not applicable
A (H3N2)	4	0	4	0	14	14 (100%)
A (H1N1)	0	0	0	0	0	0
B	2	0	2	0	NA *	NA *
TOTAL	6	0	6	0	14	14 (100%)

Influenza-like Illness (ILI) Consultation Rate

The national influenza-like-illness (ILI) consultation rate in week 44 increased from the previous week from 19.6 to 21.9 ILI consultations per 1,000 patient visits; but remains within the expected levels for this time of year (Figure 7). The highest consultation rates were observed in children less than 5 years of age (80.1/1,000) and children 5-19 years of age (37.4/1,000).

Figure 7. Influenza-like illness (ILI) consultation rates, Canada, by report week, 2012-2013 compared to 1996/97 through to 2011/12 seasons (with pandemic data suppressed)

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.

Text equivalent for figure 7Influenza-like illness (ILI) consultation rates, Canada, by report week, 2011-2012 compared to 1996/97 through to 2010/11 seasons (with pandemic data suppressed)

Severe Respiratory Illness Surveillance

Paediatric Influenza Hospitalizations and Deaths (IMPACT)
Since the start of the 2012-13 season, one laboratory-confirmed influenza-associated paediatric (16 years of age and under) hospitalization has been reported by the Immunization Monitoring Program Active (IMPACT) network. The hospitalization was reported in Saskatchewan in week 42, in a child between 10 and 16 years of age with influenza A.

Note: The number of hospitalizations reported through IMPACT represents a subset of all influenza-associate paediatric hospitalizations in Canada.

Influenza Hospitalizations and Deaths (Aggregate Surveillance System)
In week 44, 11 laboratory-confirmed influenza A-associated hospitalizations were reported [ON(5), MB(1), AB(5)]. Of these, eight were aged ≥65 years, one between 45-64 years, one between 5-9 years and one < 1 year. Among the 11 influenza A hospitalizations, nine were Influenza A/H3N2 and two were unsubtyped. None of these cases were admitted to the Intensive Care Unit (ICU), and there were no deaths.

To date this season, 27 influenza A-associated hospitalizations have been reported from four provinces (AB, MB, ON and NL). The majority of the cases (81.5%; 22/27) were ≥ 65 years of age. Of the influenza A hospitalizations for which subtype was available, 13.0% (3/23) were due to influenza A(H1N1)pdm09 and 87.0% (20/23) were due to A(H3N2). There have been three hospitalizations for which admission to ICU was required (from NL and AB). To date this season, no influenza-associated deaths have been reported.

Note: Influenza-associated hospitalizations are not reported to PHAC by the following Provinces and Territory: BC, NU, QC, NS, and NB. Only hospitalizations that require intensive medical care are reported by SK. ICU admissions are not reported in ON.

International Influenza Update

WHO: Increasing detections of influenza viruses are reported in many countries in the temperate regions of the Northern Hemisphere, particularly in North America and Western Europe. Active influenza transmission has been reported in recent weeks in several countries in tropical areas, including circulation of influenza B in Nicaragua and Costa Rica, and a mixture of all three virus subtypes in Asia. In Sub-Saharan Africa, Cameroon and Ethiopia have reported an increase in influenza virus detections. Countries in the temperate regions of the Southern Hemisphere report inter-seasonal levels of influenza detections. A review of the 2012 southern hemisphere influenza season was published in the Weekly Epidemiological Record (WER) 2 November 2012, vol. 87, 44 (pp. 421–436)
World Health Organization influenza update

United States: During week 43, influenza activity remained low in the United States with only 5 states reporting local influenza activity and the rest reporting sporadic or no activity. The proportion of tests positive for influenza viruses was the same in week 43 (6.2%) compared to the previous week. Of the positive influenza detections reported during week 43, 63% were positive for influenza A viruses. Of the 60 influenza A viruses for which subtype information was available, 98% were A(H3) and 2% were A(H1N1)pdm09. Since October 1, 2012, the CDC has antigenically characterized 10 influenza viruses: nine were influenza A (all characterized as A/Victoria/361/2011-like) and one influenza B virus (B/Wisconsin/01/2010-like). All other indicators of influenza activity remained low, although the severe weather in the eastern US may have delayed reporting in these areas.
Centers for Disease Control and Prevention seasonal influenza report

Europe: In week 44, influenza activity in Europe remained low with only a few countries reporting sporadic influenza detections. A total of 62 specimens tested positive for influenza in week 44, of which 74.2% were for influenza A viruses. Since week 40, 200 specimens of influenza viruses have been typed: 138 (69%) were influenza A and 62 (31%) were influenza B. Among the influenza A specimens for which subtype information was available (n=76), 43 (57%) were A(H3) and 33 (43%) were A(H1N1)pdm09. In general ILI and ARI consultation rates remain low and stable, without any significant geographic differences in terms of spread.
EuroFlu weekly electronic bulletin

Human Avian and Swine Influenza Updates

Human Avian Influenza
No cases of human avian influenza A/H5N1 infection have been reported by the WHO since August 10, 2012.
WHO Avian influenza situation updates

Human Swine Influenza
No new human cases of infection with swine influenza viruses or variants were reported this week.

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Definitions for the 2012-2013 season

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