July 4 to July 17, 2010 (Weeks 27 & 28)

Posted 2010-07-23

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Overall Influenza Summary - Week 27 & 28 (July 4 to July 17, 2010)

Overall influenza activity has remained low since the beginning of 2010. In week 27, six regions (in BC, AB, ON & QC) reported sporadic activity and 43 regions reported no activity. One additional region reported sporadic activity during week 28 (BC, AB, ON, QC & YK). Five regions (1 in BC, the only one in PEI and all 3 in SK) have stopped reporting for the remainder of the season. No influenza outbreaks were reported in weeks 27-28.

Map of overall Influenza activity level by province and territory, Canada, Week 28
	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 27 and 28, the national ILI consultation rates (6.6 and 8.4 per 1,000 consultations, respectively) remained low. The national rates for each week were within expected levels for this time of year (see ILI graph). Those between 20 and 64 years of age had the highest consultation rates for week 27 (9.7 per 1,000) while those between 5 and 19 years of age were the most affected during week 28 with a rate of 21.5 per 1,000 patient visits.

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 27 was 0.19% (2/1,042) and during week 28 was (0.42%, 4/963) and remained at a low level for this time of year (see Tests table). Of the six positive specimens, one specimen was reported as pandemic H1N1 2009, one for influenza A/H3N2, two were unsubtyped influenza A and the other two were positive for influenza B. BC, AB and QC were the only provinces to report positive influenza specimens during those reporting weeks. During weeks 27 and 28, the proportion of positive parainfluenza tests (9.6% and 8.1% for week 27 and 28, respectively) remained high while low levels of adenovirus (3.4% and 2.0%), respiratory syncytial virus (RSV) (1.9% and 0.9%), and human metapneumovirus (0.5% and 0.1%) detections 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 (July 4 to July 17, 2010)						Cumulative (Aug. 30, 2009 to July 17, 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	2	0	1	1	0	0	6386	0	2	5819	565	2
AB	1	0	0	0	1	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	7825	4	1	3571	4249	12
QC	1	0	0	0	1	2	10706	4	44	10653	5	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	4	0	1	1	2	2	38995	11	54	33528	5402	29

 

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 27-28, 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. Please note that delays in the reporting of data may cause data to change retrospectively.

Adult Influenza Hospitalizations and Deaths

During weeks 27 and 28, 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 8 reporting sites. From November 22, 2009 to May 22, 2010, 57 laboratory-confirmed influenza cases among hospitalized adults were reported through CNISP sentinel sites. The last hospitalized case was reported during week 1. 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 27 and 28, 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 the past two weeks were Tamiflu.  During the two-week period, general “respiratory over the counter products” trends demonstrate a decline or leveling-off among all provinces and territories. However, in week 27, Yukon showed an increase over the past week of general “respiratory over the counter products” sales.

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 influenza A/H1N1 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. 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. All resistant cases were associated with oseltamivir treatment or prophylaxis.

International influenza update

Global information

WHO: Given the diverse pattern of influenza activity in the tropics and that the influenza season in the Southern Hemisphere is still ongoing, WHO declared on July 21, 2010 that it is too early to determine if these countries have transitioned to levels and patterns expected for seasonal influenza.

<http://www.who.int/csr/disease/swineflu/notes/briefing_20100721/en/index.html>
As of July 12, 2010, over 214 countries and overseas territories or communities worldwide reported cases of pandemic H1N1 2009 (at least 18,337 deaths). Worldwide, overall pandemic and seasonal influenza activity remained low. The most active areas of pandemic influenza virus transmission currently were in parts of South Asia, West Africa, and Central America. In the temperate zone of the southern hemisphere, pandemic and seasonal influenza activity has remained low during the first half of the southern hemisphere winter, except in South Africa, where increased detections of primarily seasonal influenza viruses (type B and H3N2) were reported during late June and early July 2010. Seasonal influenza H3N2 viruses continue to circulate at varying levels across parts of the Americas, Africa, and Southeast Asia. Increased seasonal influenza activity continues to be observed in several countries of Central America. <http://www.who.int/csr/don/2010_07_16/en/index.html>

Antiviral resistance: As of July 14, 2010, 298 pandemic H1N1 2009 isolates worldwide have been found to be resistant to oseltamivir. All but one of these had the H275Y substitution and were assumed to remain sensitive to zanamivir. <http://www.who.int/csr/disease/swineflu/oseltamivirresistant20100716.pdf>

Geographic update

Southern hemisphere

South Africa began observing a sharp increase in the proportion of sentinel respiratory samples testing positive for influenza virus (primarily seasonal influenza B and H3N2) during late June 2010, reaching a peak of ~50% detection rate during the first week of July 2010, and falling to ~40% during the second week of July 2010. In Chile (as of late June 2010) and Argentina (as of early July 2010), the most recent available data showed that influenza activity remained sporadic in Argentina and low in Chile. In both Chile and Argentina, RSV has been the predominant circulating respiratory virus since mid-April 2010. In Australia, although a small cluster of pandemic influenza cases, including a few hospitalized cases, were recently detected in the Northern Territory of Australia, pandemic and seasonal influenza virus detections remained otherwise sporadic, albeit slightly increased during late June and early July 2010. Similarly, in New Zealand, rates of ILI have remained low and below the seasonal baseline, with only sporadic detections of pandemic and seasonal H3N2 viruses through the first week of July 2010. In both Australia and New Zealand, current levels of ILI are similar to those observed during the same period in 2008, when the influenza season was noted to have arrived and peaked late in winter. <http://www.who.int/csr/don/2010_07_16/en/index.html>

Northern hemisphere

Central America & the Caribbean: In the tropical regions of the Americas, overall pandemic and seasonal influenza activity remained low, except in parts of Central and South America, where there has been recent active co-circulation of pandemic and seasonal influenza H3N2 viruses. The majority of recent active transmission of pandemic influenza virus has been reported in Colombia, Costa Rica, and to a lesser extent in Cuba. <http://www.who.int/csr/don/2010_07_16/en/index.html>

Africa: In sub-Saharan Africa, the situation was largely unchanged since the last update. <http://www.who.int/csr/don/2010_07_16/en/index.html>

Asia: In Asia, overall pandemic influenza activity remained low to sporadic, except in parts of southern and western India, Malaysia, and Singapore. Substantial co-circulation of pandemic H1N1 virus and seasonal influenza H3N2 viruses was detected in Singapore throughout May and June 2010. Low levels of seasonal influenza type B viruses (and to much lesser extent pandemic influenza virus) continue to circulate across northern and southern China. <http://www.who.int/csr/don/2010_07_16/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 26 and 27, low intensity was reported by 16 countries. Only four (6.9%) sentinel specimens were positive for influenza during week 26 and 27 and all of them were of type B. <http://ecdc.europa.eu/en/publications/Publications/100716_SUR_Weekly_Influenza_Surveillance_Overview.pdf>

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Definitions for the 2009-2010 season