July 19, 2009 to July 25, 2009 (Week 29)

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Pandemic (H1N1) 2009 virus Surveillance and Epidemiology

A total of 1,271 hospitalized cases, 219 cases admitted to ICU and 57 deaths of Pandemic (H1N1) 2009 have been reported to PHAC as of July 25, 2009. National abbreviated line list data was available for 6,814 cases, 1,234 (18.1%) hospitalized cases including 219 (17.7%) patients admitted to ICU and 51 deaths. The proportion of females affected, the median age and the proportion of underlying medical conditions is increasing with severity of illness. There is also a high proportion of pregnant women within the severe cases (21.9% for hospitalized cases and 33.3% among deaths). The age distribution was available for 1,193 hospitalized cases and 43 deaths from the abbreviated line list. The highest hospitalization rate is among the cases below 1 year of age (25.1 per 100,000) followed by the cases between 1 and 4 years of age (10.0 per 100,000). In comparison, the highest mortality rate is among the cases over 65 years of age (0.33 per 100,000), followed closely by the cases below 1 year of age (0.27 per 100,000) and cases between 45 and 64 years old (0.20 per 100,000). While cases aged under 15 years old have the highest hospitalization rate, they have one of the lowest mortality rate except for children under 1 year of age. In comparison, adults over 65 years old have the lowest hospitalization rate, but one of the highest mortality rates along with those under 1 year old.

There were 677 Canadian cases who were Aboriginal. First Nations cases (180) were from Manitoba (144), British Columbia (14), Alberta (11), Quebec (8) and Northwest territories (3). 419 Inuit cases were from Nunavut and the rest from Alberta (3) and Northwest Territories (2). Finally, Metis cases (73) were from QC (35), MB (30), AB (4), NWT (3) and BC (1). The median age for the First Nations cases reported was 18 years as compared to 10 years for the Nunavut residents and Inuit from other provinces. The proportion of cases that were female is higher among the Nunavut residents and the other Inuit cases in Canada (55.7%) compared to the First Nations population (46.7%). Among the 56 hospitalized First Nations cases, 33.9% were either admitted ICU or death in comparison to 12.5% (3/24) from the Nunavut residents and the Inuit from other provinces.

Weekly and cumulative numbers of hospitalizations and deaths among
Pandemic (H1N1) 2009 confirmed cases, Canada, to 25 July, 2009

Province/Territory	This week (19-25 July, 2009) hospitalized cases	This week (19-25 July, 2009) deaths	Cumulative hospitalized cases	Cumulative deaths cases
BC	9	1	25	2
AB	21	1	114	4
SK	9	0	22	4
MB	0	1	201	7
ON	13	2	290	18
QC	76	2	564	20
NB	0	0	1	0
NS	1	1	10	1
PE	0	0	1	0
NL	1	0	1	0
YT	0	0	0	0
NT	0	0	0	0
NU	0	0	42	1
Canada	130	8	1271	57

 

Descriptive characteristics of laboratory-confirmed Canadian Pandemic (H1N1) 2009 cases, hospitalized cases, cases admitted to ICU and deaths with core information available, reported to the Public Health Agency of Canada as of 25 July 2009

	Overall cases reported (n=6,814)	Hospitalizated cases (n=1,234)	Cases admitted to ICU (n=219)	Deaths (n=51)
Females, %	51.7	51.0	60.7	62.8
Median age	18	23	40	54
Aboriginal status, %	10.0	10.3	11.0	5.9
Underlying medical conditions1, %	50.9 (572/1,124)	61.1 (502/821)	71.1 (123/173)	83.8 (31/37)
Pregnancy2, %	3.2 (52/1,638)	21.9 (48/219)	16.7 (10/60)	33.3 (2/6)
1 Among those for whom the information was provided. 2 Among women aged between 15 and 44.

Overall Influenza Summary - July 19, 2009 to July 25, 2009 (Week 29)

The overall influenza activity decreased slightly this week ; the national ILI consultation rate (19 consultations per 1,000 visits vs. 21) and the number of influenza outbreaks in long-term care facilites (0 vs. 2) are lower compared to the last week. In addition, the proportion of influenza positive tests decreased for the sixth consecutive week. However, 100% of the influenza A subtyped were due to Pandemic (H1N1) 2009 this week.

Six regions in ON, QC, NB & NL reported localized activity, 39 regions sporadic activity in BC, SK, ON, QC, NB, NS, PEI, NL, YT, NT & NU and 2 regions in NB reported no activity (No report received from AB, MB and 1 region in ON). Four new influenza outbreaks were reported this week; two in hospital (ON & NL), one in a workplace (NB) and one occured in unspecified locations (ON).

Map of overall Influenza activity level
by provinces and territories, Week 29 Canada

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, 2008-2009 (N=54)

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

Number of New Outbreaks in Long Term Care Facilities, Canada, by Report Week, 2008-2009

ILI consultation rate

This week, the ILI consultation rate was 19 consultations per 1,000 patient visits (see ILI graph) which represents an decrease compared to the previous week. The sentinel response rate was 76.6%.

Influenza-like illness (ILI) consultation rates, Canada, by report week,
2008-2009 compared to 1996/97 through to 2007/08 seasons

Note: No data available for mean rate in previous years for weeks 19 to 39 (1996-1997 through 2002-2003 seasons).
* Data arriving late may cause variations from results seen in previous weeks.

Paediatric Influenza Hospitalizations and deaths

In week 29, 2 laboratory-confirmed influenza-associated paediatric hospitalizations were reported through the Immunization Monitoring Program Active (IMPACT) network. These two hospitalizations were due to Pandemic (H1N1) 2009. To date this season, 726 hospitalizations have been reported; 314 (43.3%) of hospitalizations have been due to Pandemic (H1N1) 2009. There were five deaths reported so far this season including three deaths due to Pandemic (H1N1) 2009 (two from BC and three from QC).

Laboratory Surveillance Summary

This week, the proportion of tests that were positive for influenza was 10.1% which is decreasing for the sixth consecutive week (see table). A total of 538 specimen tested positive for influenza this week (536 A and 2 B). All the positive influenza A subtyped specimens were due to Pandemic (H1N1) 2009 this week. The majority (82.4%) of influenza virus detections this season have been for influenza A.

Influenza tests reported and percentage of tests positive, Canada,
by report week, 2008-2009

Percent positive influenza tests, compared to other respiratory viruses, Canada, by reporting week, 2008-2009

Weekly & Cummulative numbers of positive influenza specimens , by Provincial Laboratories

Reporting  provinces	Weekly						Cumulative
	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	83	0	0	66	17	0	1478	9	9	427	1033	210
AB	159	0	0	70	89	0	2817	0	8	598	2211	467
SK	37	0	0	28	9	0	1382	31	79	845	427	219
MB	13	0	0	11	2	0	1050	7	35	750	258	37
ON	71	0	0	12	59	1	6556	146	156	2933	3321	1355
QC	32	0	0	0	32	1	3833	0	0	0	3833	1417
NB	49	0	0	27	22	0	366	3	3	49	311	95
NS	78	0	0	73	5	0	520	23	23	390	84	60
PE	2	0	0	2	0	0	28	5	0	9	14	9
NL	12	0	0	12	0	0	195	11	4	57	123	26
Canada	536	0	0	301	235	2	18225	235	317	6058	11615	3895

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.
* Not subtyped

Canadian situation

Antigenic Characterization

NML has antigenically characterized 234 Pandemic (H1N1) 2009 isolates by HI assay. The results reveal that these viruses are antigenically related to A/California/7/2009 (H1N1), which is the variant reference virus selected by WHO as a potential candidate for Pandemic (H1N1) 2009 vaccine. Antigenic characterization also indicates that these viruses are antigenically and genetically unrelated to seasonal influenza A (H1N1) viruses, which suggests that there is little or no protection to be expected from vaccination with seasonal influenza vaccine.

Antiviral Resistance

NML: All Pandemic (H1N1) 2009 viruses tested so far have been sensitive to oseltamivir (400 samples) and zanamivir (215 samples) but resistant to amantadine (283 samples).

First canadian oseltamivir-resistant Pandemic (H1N1) 2009: Canada reported its first case of oseltamivir resistant pandemic influenza A (H1N1) on July 21, 2009. The strain was isolated from a 59 year old male from Quebec with underlying medical conditions who received post-exposure prophylaxis following illness in a family member (the man's son). The isolate had a mutation at the H274Y location. The father was tested due to onset of symptoms while on antiviral medication. Provincial health authorities are not aware of any additional secondary infections in the family and report that the oseltamivir resistant case remained at home during his infectious period, except for one occasion during which he was wearing a mask. Both the father and son had mild illnesses and have fully recovered. Sequencing data for the son (family index case) showed that his strain was sensitive to oseltamivir; both strains were sensitive to zanamivir. Investigation is under way. No second case identified so far.

Animal Surveillance

Quebec finds pandemic H1N1 in a pig herd: An isolated case of the pandemic strain of H1N1 influenza has been confirmed in a Quebec pig herd that has since completely recovered. No other case has been reported on any other pig farm in Quebec and there have been no human cases related to this situation. It is not known how the pig caught the virus.

International update:

Surveillance

Japan has detected two more Tamiflu-resistant H1N1 cases: Alexander Klimov of the CDC's flu surveillance branch also said that Chinese officials revealed during a WHO conference call that they may have one more antiviral-resistant case. All but one of the cases so far have been linked to Tamiflu prophylaxis or treatment.

Southern hemisphere sees H3N2 seasonal flu variant: Laboratory experts in the southern hemisphere are reporting the circulation of a drifted strain of the seasonal H3N2 influenza virus, raising the threat of a vaccine mismatch for the northern hemisphere's upcoming flu season.

Southern Hemisphere

• Australia : As of July 30, 2009, Australia has 20,688 confirmed cases (559 new cases in the past 24 hrs) and 58 deaths. There are currently 410 people in hospital across Australia with Pandemic (H1N1) 2009, and 110 (27%) of these are in intensive care units (total hospitalizations 2,394).
• New Zealand: As of July 30, 2009, the total number of confirmed cases in New Zealand is 2,769 (up 21 cases since in the past 24 hrs), and 13 deaths. Among influenza viruses reported from all surveillance sources in week 30, the majority of them (approximately 72%) were Pandemic (H1N1) 2009.
• South Africa: As of July 24, South Africa reported a total of 151 cases of Pandemic (H1N1) 2009. For week 29, ending July 19, influenza isolates from all surveillance sources were detected in the following proportions: 84% A(H3N2), 10% Pandemic H1N1 2009, 4% influenza A (awaiting typing), 2% influenza B, and <1% seasonal influenza A(H1N1).
  • NICD <http://www.nicd.ac.za/>
• Argentina: As of July 14, a total of 3,056 cases of Pandemic (H1N1) 2009, and 137 deaths have been reported. In one of the hardest hit provinces, Santa Fe, 77 deaths have been reported (47 females, 30 males) of whom 19 cases had no underlying medical conditions. The median age of fatal cases is 45 years.
• Chile: As of July 23, the number of confirmed cases in Chile is 11,641. 7.3% of cases have been hospitalized, and 79 have died (an increase of 11 deaths since July 20, now 0.7% of confirmed cases). Sixty percent of cases are in children, 0-19 years. The median age of 854 severe cases is 29 years (ranging from 11 days to 94 years), with 43% of cases reported to have underlying conditions. Of the 66 fatal cases for which Pandemic (H1N1) 2009 has been attributed as a contributing cause of death, 68% of patients were male, the median age was 46 years, and 53% had underlying medical conditions.

Northern Hemisphere

• Japan: As of July 24, 2009, Japan reports 5,015 confirmed cases (up 553 since July 22nd) of Pandemic (H1N1) 2009 and no deaths.
• United States: As of July 24, 2009, the CDC reports 43,711 confirmed and probable infections with Pandemic (H1N1) 2009 and 302 deaths. Over 99% of subtyped influenza A viruses reported to CDC during week 28 (July 12-18, 2009) were Pandemic (H1N1) 2009.
• United Kingdom: The National Pandemic Flu Service (NPFS) was launched in England on July 23. Antiviral drugs are authorized to people with an influenza-like illness who call or log onto the internet site. It has been estimated that the overall number of cases in England is still rising, though the rate of increase is slowing; HPA modeling gives an estimate of 110,000 new cases in England in week 30 (range 60,000 – 160,000), compared to an estimated 100,000 in the previous week. The cumulative number of deaths reported due to Pandemic (H1N1) 2009 in the UK is 31. On July 28, there were 793 inpatients in hospitals in England with suspected Pandemic influenza (up 268 in the previous 24 hours). The highest hospitalization rate has consistently been in the under 5-year group. Hospitalization rates have remained stable over the past two weeks.

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FluWatch reports include data and information from five main sources: laboratory reports of positive influenza tests in Canada; sentinel physician reporting of influenza-like illness (ILI); provincial/territorial assessment of influenza activity based on various indicators, including laboratory surveillance, ILI reporting, school and work site absenteeism, and outbreaks; influenza-associated pediatric hospitalizations; WHO and other international reports of influenza activity.
The map shows influenza activity in the “influenza surveillance regions” † within each jurisdiction, as determined by the provincial/territorial epidemiologists.

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).

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Definitions for the 2008-2009 season