August 1 to August 14, 2010 (Weeks 31 & 32)

Posted 2010-08-20

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Overall Influenza Summary – Weeks 31 & 32 (August 1 to August 14, 2010)

Overall influenza activity has remained low since the beginning of 2010. In weeks 31 and 32, four regions reported sporadic activity (1 in BC, 1 in AB and 2 in QC during week 31 as well as 1 in BC and 3 in QC in week 32). A total of 45 regions reported no activity in week 31 and 44 regions in week 32. Five regions (1 in BC, PEI and all 3 in SK) have stopped reporting for the remainder of the season. Two additional regions in NL did not report during week 32. No influenza outbreaks were reported in weeks 31-32.

Map of overall Influenza activity level by province and territory, Canada, Week 32
	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.

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

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 weeks 31 and 32, the national ILI consultation rates (4.5 and 7.6 per 1,000 consultations, respectively) remained similar to the previous weeks and were within expected levels for this time of year (see ILI graph). Those between 5 and 19 years of age had the highest consultation rates during weeks 31 and 32 (9.8 and 21.1 per 1,000 patient visits, respectively). Note that over the summer months, weekly ILI consultation rates are unstable due to significant drops in sentinel response rates compared to the regular influenza season (i.e. 67% response rate in week 5 and 35% and 39% in weeks 31 and 32, respectively).

Influenza-like illness (ILI) consultation rates, Canada, by report week,
2009-2010 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.

Laboratory Surveillance Summary

The proportion of tests that were positive for influenza during week 31 was 0.0% (0/708) and during week 32 was 0.27% (2/732), with a combined proportion of 0.14% (2/1,440) for the two-week period (see Tests table). The two positive specimens were reported as unsubtyped influenza A (BC and QC). Note that the proportion of positive influenza tests has remained under 1% since week 2. During weeks 31 and 32, the proportion of positive parainfluenza tests (4.4% and 6.6% for week 31 and 32, respectively) remained high and at a level similar to the previous weeks while low levels of adenovirus detections (1.9 % and 0.5%), respiratory syncytial virus (RSV) (0.43% and 0.14%) continue to be reported.

Bi-Weekly & Cumulative numbers of positive influenza specimens by Provincial Laboratories, Canada, 2009-2010

*Not subtyped. 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	Bi-Weekly (August 1 to August 14, 2010)						Cumulative (August 30, 2009 to August 14, 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	1	0	0	0	1	0	6388	0	3	5819	566	2
AB	0	0	0	0	0	0	5873	2	5	5764	102	3
SK	0	0	0	0	0	0	2598	0	1	2298	299	0
MB	0	0	0	0	0	0	1915	0	0	1788	127	0
ON	0	0	0	0	0	0	7807	4	1	3552	4250	13
QC	1	0	0	0	1	0	10708	4	44	10653	7	11
NB	0	0	0	0	0	0	1856	1	1	1835	19	0
NS	0	0	0	0	0	0	788	0	0	753	35	1
PE	0	0	0	0	0	0	97	0	0	96	1	0
NL	0	0	0	0	0	0	951	0	0	951	0	0
Canada	2	0	0	0	2	0	38981	11	55	33509	5406	30

 

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

Canadian situation

Paediatric Influenza Hospitalizations and Deaths

In weeks 31-32 no laboratory-confirmed influenza-associated paediatric (18 years of age and under) hospitalizations were reported through the Immunization Monitoring Program Active (IMPACT) network. Since the beginning of the 2009-2010 influenza season (30 August, 2009), 952 hospitalizations have been reported, of which 97.7% were due to pandemic H1N1 2009. The last hospitalized case was reported during week 15 with pandemic H1N1 2009. Please note that delays in the reporting of data may cause data to change retrospectively.

Adult Influenza Hospitalizations and Deaths

During weeks 31 and 32, 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 9 reporting sites in week 31 and 11 in week 32. From November 22, 2009 to May 22, 2010, 57 laboratory-confirmed influenza cases among hospitalized adults (16 years of age and older) were reported through the Canadian Nosocomial Infection Surveillance Program (CNISP) sentinel sites. The last hospitalized case was reported during week 1 with pandemic H1N1 2009. Please note the total number of CNISP reporting sites fluctuates weekly and most of the reporting sites started surveillance in late fall 2009.

Sale of antivirals (AV) 

During weeks 31 and 32, little change in antiviral prescription sales were observed among provinces and territories. Daily and weekly antiviral data at the Health Region level demonstrated low antiviral prescription rates among all Health Regions for the report weeks. All the antivirals sold from participating retail pharmacy chains and stores during the past two weeks were Tamiflu. At the national level, the rise in respiratory-related over-the-counter transactions which began during week 31 appears to have leveled-off. Several provinces and territories appear to be driving this recent trend. Interestingly, respiratory-related OTCs began to increase last year at this same time.

Antigenic Characterization 

Since September 1, 2009, the National Microbiology Laboratory (NML) has antigenically characterized 858 (98.1%) influenza A/H1N1, 10 (1.1%) influenza A/H3N2 and 7 (0.8%) influenza B viruses that were received from provincial laboratories. Of the 858 pandemic H1N1 2009 viruses characterized, 855 (99.7%) were antigenically related to A/California/7/2009, which is the pandemic reference virus selected by WHO for the pandemic H1N1 2009 vaccine and three (0.3%) were A/Brisbane/59/2007-like. Four viruses (0.5%) tested showed reduced titer with antisera produced against A/California/7/09. Of the 10 influenza A/H3N2 viruses characterized, two were related to A/Brisbane/10/07 (2009-10 vaccine) and eight viruses were antigenically related to A/Perth/16/09 (2010-2011 Northern Hemisphere vaccine). Of the 7 influenza B viruses characterized, 5 were antigenically related to B/Brisbane/60/08 (2009-10 vaccine), one was antigenically similar to B/Malaysia/2506/2004 and one was related to the previous vaccine virus B/Florida/4/2006.

Antiviral Resistance 

Since August 30, 2009, 12 cases of oseltamivir resistant pandemic H1N1 2009 were reported to date in Canada while one was reported in the 2008-2009 influenza season. The last two cases were reported during week 5. All resistant cases were associated with oseltamivir treatment or prophylaxis.

International influenza update

Global information

WHO: The World Health Organization declared on August 11, 2010 that the world is no longer in phase 6 of influenza pandemic alert and has moved into the post-pandemic period. However, the influenza H1N1 2009 transmission remained locally intense in parts of India and New Zealand. Seasonal influenza A/H3N2 viruses have recently circulated in the tropics of the Americas (particularly in several Central American countries), in southern and western Africa, and in parts of Southeast Asia. The most active areas of influenza type B virus circulation continue to be in parts of central and southern Africa.
<http://www.who.int/mediacentre/news/statements/2010/h1n1_vpc_20100810/en/index.html> <http://www.who.int/csr/don/2010_08_13/en/index.html>

Geographic update

Southern hemisphere

Australia: In Australia, the levels of influenza-like illness (ILI) in the community continued to show signs of increasing. The notifications of laboratory confirmed influenza continue to increase, indicating the start of the influenza season. There have been 115 laboratory confirmed notifications of influenza during this week 31, including 67 (58.3%) pandemic H1N1 2009 cases.
<http://www.healthemergency.gov.au/internet/healthemergency/publishing.nsf/Content/ozflu2010-jul-sep-pdf-cnt.htm/$File/ozflu-no31-2010.pdf>

New Zealand: The national ILI consultation rate was 143.8 per 100 000 consultations during week 32 which is above the baseline level. A total of 131 swabs were received by virology laboratories from sentinel surveillance. Of these, 56 (42.7%) influenza viruses were identified: pandemic H1N1 2009 (30.5%) and A (not sub-typed) (12.2%). Nationally, overall rates of ILI and numbers of severe and fatal cases remained well below levels seen during the winter 2009 pandemic wave, however, the situation continues to evolve and the current epidemic has yet to peak.
<http://www.who.int/csr/don/2010_08_13/en/index.html>
<http://www.surv.esr.cri.nz/PDF_surveillance/Virology/FluWeekRpt/2010/FluWeekRpt201032.pdf>

Northern hemisphere

India: In India, the number of new H1N1 (2009) cases per week, including fatal cases, continued to increase since mid June 2010 in several states. Overall, 79 new laboratory confirmed H1N1 (2009) associated deaths were officially reported across India during the week of August 2-8. Seasonal influenza B viruses are also known to be currently circulating in India, although at lower levels than H1N1 (2009) viruses.
<http://www.who.int/csr/don/2010_08_13/en/index.html>

United States: No further influenza surveillance reports will be published by the CDC for the 2009-2010 influenza season (last report was in week 20). The next report will be for week 40 (week ending October 9, 2010) during the 2010-2011 influenza season.
<http://www.cdc.gov/flu/weekly/index.htm>

Europe: During weeks 30 and 31, epidemiological indicators did not show any influenza activity in 19 reporting countries. Influenza B and A/H3N2 viruses were sporadically detected in sentinel and non-sentinel specimens during weeks 30–31/2010.
<http://ecdc.europa.eu/en/publications/Publications/100813_SUR_Biweekly_Influenza_Surveillance_Overview.pdf>

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