Australian influenza report 2010 - 20 to 26 February 2010 (#8/10)

The Australian Influenza Report is compiled from a number of data sources, including laboratory-confirmed notifications to NNDSS, sentinel influenza-like illness reporting from general practitioners and emergency departments, workplace absenteeism, and laboratory testing. A more in-depth annual report is also published in Communicable Diseases Intelligence.

Page last updated: 10 March 2010

Report No. 8
Week ending 26 February 2010

A print friendly version of this report is available as a PDF (231 KB)

Key Indicators

The counting of every case of pandemic influenza is no longer feasible in the PROTECT phase. Influenza activity and severity in the community is instead monitored by the surveillance systems listed below.

Is the situation changing?

Indicated by laboratory confirmed cases reported to NetEpi and/or National Notifiable Diseases Surveillance System (NNDSS); GP Sentinel influenza-like illness (ILI) Surveillance; and emergency department (ED) presentations of ILI at sentinel hospitals (New South Wales and Western Australia).

Laboratory data are used to determine the proportion of pandemic (H1N1) 2009 influenza circulating in the community.
How severe is the disease, and is severity changing?
Indicated by number of hospitalisations, ICU admissions and deaths from sentinel hospital surveillance as well as emergence of more severe clinical picture in hospitalised cases and ICU admissions.
Is the virus changing?
Indicated by emergence of drug resistance or gene drift or shift from laboratory surveillance.


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Summary

  • In 2010, as at 26 February, there were 44 confirmed cases of pandemic (H1N1) 2009 influenza reported in Australia, bringing the total of confirmed cases to 37,680 since 2009. In addition, there were 186 reported cases of influenza type A not sub-typed.
  • National influenza activity remains low. However, some indicators are at levels slightly above those experienced at the same time in previous years:
    • Enquiries to the National Health Call Centre Network (NHCCN) remain low;
    • There has been no change in ILI presentation rates to General Practitioners, at 5 patients per 1,000 visits;
    • ILI presentations to emergency departments (EDs) in New South Wales and Western Australia were slightly above levels seen at the same time in previous years;
    • FluTracking shows a slight increase in ILI nationally; and
    • Absenteeism rates have increased and are above levels seen at the same time in previous years.
  • As at 21 February 2010, the WHO Regional Offices reported at least 16,226 deaths associated with pandemic (H1N1) 2009 influenza worldwide. In the Northern Hemisphere, active but declining pandemic influenza transmission persists in areas of Eastern and South Eastern Europe, Eastern and South East Asia.
  • Pandemic (H1N1) 2009 influenza virus continues to be the predominant influenza virus circulating worldwide. In China and Hong Kong, however, seasonal influenza type B viruses accounted for 83.5% and 56.1% of all influenza detected in the reporting week, respectively.
The substantial rise in seasonal influenza type B in Hong Kong (from 34.5% in the last reporting week) is similar to the recent trend seen earlier in China.

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1. Influenza activity in Australia

Laboratory Confirmed Cases

There were three new laboratory confirmed pandemic (H1N1) 2009 notifications reported this reporting period. Pandemic influenza activity remains low and sporadic cases of pandemic influenza continue to be reported without evidence of sustained community transmission. In the same period, there were 48 cases of influenza A not sub-typed (Figures 1 and 2).

There were 37,680 confirmed cases of pandemic (H1N1) 2009 in Australia as at 26 February 2010, including 191 pandemic influenza-associated deaths. Of these, 37,636 cases were reported in 2009 and 44 cases were reported in 2010.

Figure 1. Laboratory confirmed cases of pandemic (H1N1) 2009 in Australia, to 26 February 2010
Figure 1. Laboratory confirmed cases of pandemic (H1N1) 2009 in Australia, to 26 February 2010

Source: NetEPI database



Figure 2. Laboratory confirmed cases of influenza (pandemic (H1N1) 2009 and seasonal) in Australia, 2010 to 26 February, by week and type

Figure 2. Laboratory confirmed cases of influenza (pandemic (H1N1) 2009 and seasonal) in Australia, 2010 to 26 February, by week and type

Source: pandemic (H1N1) 2009 cases from NetEPI; seasonal influenza from NNDSS.


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Influenza-Like Illness

Sentinel General Practice Surveillance

Combined data available from the Australian Sentinel Practices Research Network (ASPREN) and the Northern Territory GP surveillance system, up until 21 February 2010, show that nationally, ILI consultation rates remained low and are consistent with levels seen in 2008 and 2009 (Figure 3).

In the last week, the presentation rate to sentinel GPs in Australia was approximately 5 cases per 1,000 patients seen.

Figure 3. Weekly rate of ILI reported from GP ILI surveillance systems from 1 January 2007 to 21 February 2010*

Figure 3. Weekly rate of ILI reported from GP ILI surveillance systems from 1 January 2007 to 21 February 2010

* Delays in the reporting of data may cause data to change retrospectively. As data from the NT surveillance system is combined with ASPREN data for 2010, rates may not be directly comparable across 2007, 2008 and 2009.
SOURCE: ASPREN, and NT GP surveillance system.


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WA emergency departments

The number of ILI presentations reported in Western Australian EDs remained similar to the previous reporting period in the week ending 21 February 2010 and are slightly above levels seen at the same time in previous years (Figure 4).

Figure 4. Number of Emergency Department presentations due to ILI in Western Australia from 1 January 2007 to 21 February 2010 by week

Figure 4. Number of Emergency Department presentations due to ILI in Western Australia from 1 January 2007 to 21 February 2010 by week

Source: WA ‘Virus Watch’ Report


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NSW emergency departments

In January 2010, there were 95 presentations with influenza –like illness to New South Wales EDs. This is less than in the previous month (151 presentations), but is greater than the count of 65 for January 2009.

Source: NSW Health ‘Influenza Monthly Epidemiology Report1


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Flutracking

Flutracking, a national online system for collecting data on ILI in the community, reported that in the week ending 28 February 2010 there has been a slight increase in influenza-like illness levels nationally (Figure 5).

Figure 5. Rate of ILI symptoms and absence from regular duties among Flutracking participants by week (from 3 May 2009 to week ending 28 February 2010)

Figure 5. Rate of ILI symptoms and absence from regular duties among Flutracking participants by week (from 3 May 2009 to week ending 28 February 2010)

Source: Flutracking Interim Weekly Report


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National Health Call Centre Network

The number of ILI-related calls received by the NHCCN remained low in the week ending 26 February 2010 with 36 calls, compared with 59 calls in the previous reporting period. At the peak of the 2009 season, the NHCCN received approximately 1900 ILI-related calls per week. The number of calls is currently at baseline levels (Figure 6).

Figure 6. Number of calls to the NHCCN related to ILI, Australia, 1 January 2009 to 26 February 2010

Figure 6. Number of calls to the NHCCN related to ILI, Australia, 1 January 2009 to 26 February 2010

Source: NHCCN data


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Deaths associated with influenza and pneumonia

Death registration data show that as at 8 January 2010, there were 101 pneumonia or influenza deaths per 1,000 deaths in NSW, which was lower than previous weeks and was below the seasonal threshold of levels expected at that time of year (Figure 7).

Figure 7. Rate of deaths classified as influenza and pneumonia from the NSW Registered Death Certificates, 2005 – 2010

Figure 7. Rate of deaths classified as influenza and pneumonia from the NSW Registered Death Certificates, 2005 – 2010

Source: NSW ‘Influenza Monthly Epidemiology Report’


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Absenteeism

The most recent data indicate that in the week ending 17 February 2010, national absenteeism rates increased and were slightly above levels seen at the beginning of previous years (Figure 8).

Figure 8. Rates of absenteeism (greater than 3 days absent), national employer, from 28 January 2007 to 17 February 2010, by week.

Figure 8. Rates of absenteeism (greater than 3 days absent), national employer, from 28 January 2007 to 17 February 2010, by week

SOURCE: Absenteeism data


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Sentinel Laboratory Surveillance - confirmed influenza notifications

Results from sentinel laboratory surveillance systems for this reporting period show that 1.8% of the respiratory tests conducted over this period were positive for influenza (Table 1). Of the five that were positive, three were pandemic influenza, one was Type A/H3N2 and one was Type B.

Table 1. Laboratory respiratory tests that tested positive for influenza A and pandemic (H1N1) 2009 influenza

  ASPREN* – national WA NT (reported by WA NIC) Vic NIC NSW
Number of specimens tested
2
81
(at 26/2)
N/A
135
(at 26/2)
61
Number tested which were Influenza A
0
3
0
1
0
Number tested which were pandemic     (H1N1) 2009
0
2
0
1
0
Number tested which were seasonal   A/H1N1
0
0
0
0
0
Number tested which were A/H3N2
0
1
0
0
0
Number tested which were Influenza A untyped
0
0
0
0
0
Number tested which were Influenza B
0
1
0
0
0

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2. Overview of pandemic (H1N1) 2009 severity - to 26 February 2010a

While pandemic (H1N1) 2009 is generally considered a mild disease at the community level, it has had serious consequences at the acute end of the disease. Figures of hospitalisations, ICU admissions and deaths are currently used as indicators of the severity of the disease in Australia (Table 2).

a Note that while the analysis of severity is on-going, updates are presented as required when there are significant changes detected. With the current low levels of pandemic (H1N1) 2009 influenza activity in Australia it is anticipated that the indicators of pandemic severity will not vary significantly.


Pandemic (H1N1) data for 2009 are currently being finalised through cleaning and validation processes. It is possible that these processes will result in some changes in the data presented here. Validated data will be progressively reported as these steps are completed.

Table 2. Summary of severity indicators of pandemic (H1N1) in Australia, 2009

2009#
  Confirmed pandemic
(H1N1) 2009 cases
Hospitalised cases ICU cases Deaths
Total number
37,636
13% (4,992/37,636) confirmed cases)
14%
(681/4,992 hospitalisations)
191
Crude rate per 100,000 population
172.1
22.8
3.1
0.9
Median age (years)
21
31
44^
53^
Females
51% (19,139/37,636)
51% (2,528/4,992)
53%
(364/681)
44%
Vulnerable groups (Indigenous persons, pregnant women & individuals with at least 1 co-morbidity)
n/a
58% (2,892/4,992)
74%
(504/681)
67%
Indigenous people~
11% (3,877/34,750)
20%
(808/4,048)
19%
(102/533)
13%
Pregnant women*
n/a
27%
(287/1,056 hospitalised females aged
15-44 years)
16%
(47/289) hospitalised pregnant women)
4%
Cases with at least 1 co-morbidity
n/a
46% (2,303/4,992)
67%
(457/681)
62%

#Data are extracted from a number of sources depending on the availability of information. Figures used in the analysis have been provided in parentheses. Data is not always complete for each summarised figure.
~The denominator for this row is the number of confirmed cases for which Indigenous status is known.
* Includes women in the post-partum period.
^ Validation of data has identified anomalies affecting median ages for ICU cases and deaths in reports #28-33 2009 and report #1 2010. Correction has resulted in a change in the median ages of ICU cases and deaths from report #2, 2010.


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3. Virology

Antigenic characteristics - WHO Collaborating Centre for Reference & Research on Influenza (WHO CC) in Melbourne

From 1 January 2010 to 28 February 2010,11 Australian influenza isolates have been subtyped by the WHO CC (Table 3).

Table 3. Typing of influenza isolates from the WHO Collaborating Centre, from 1 January 2010 to 28 February 2010

Type/Subtype
ACT NSW NT Qld SA Tas Vic WA TOTAL
A(H1N1)
0
0
0
0
0
0
0
0
0
Pandemic (H1N1) 2009
0
0
3
0
0
1
5
1
10
A(H3N2)
0
0
0
0
0
0
0
0
0
B
0
0
0
0
0
0
1
0
1
Total
0
0
3
0
0
1
6
1
11

SOURCE: WHO CC
Please note: There may be up to a months delay on reporting of samples.
Isolates tested by the WHO CC are not necessarily a random sample of all those in the community, hence proportions of pandemic (H1N1) 2009 to seasonal are not representative of the proportions circulating.



Of the 11 influenza isolates subtyped by the WHO CC, 1 has been antigenically characterized, and confirmed as pandemic A/H1N1 2009 (A/California/7/2009-like).
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INTERNATIONAL UPDATES

The Global Influenza Surveillance Network (GISN) continues to monitor the global circulation of influenza viruses, including pandemic, seasonal and other influenza viruses infecting, or with the potential to infect, humans. Since the beginning of the pandemic on 19 April 2009 to 13 February 2010, 153 countries shared a total of 24,186 specimens (18,663 clinical samples and 5,523 virus isolates) with WHO Collaborating Centres for further characterisation.1

Pandemic (H1N1) 2009 influenza virus continues to be the predominant influenza virus circulating worldwide. In China and Hong Kong, however, seasonal influenza type B viruses accounted for 83.5% and 56.1% of all influenza detected in the reporting week, respectively. Low levels of seasonal H3N2 and type B viruses are circulating in parts of Africa and Asia. 1
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ANTIVIRAL RESISTANCE

Pandemic (H1N1) 2009

To date, WHO reported that 253 oseltamivir resistant pandemic (H1N1) 2009 viruses had been detected and characterised worldwide. All of these isolates showed the same H275Y mutation but all were sensitive to zanamivir. Of the oseltamivir resistant cases reported to WHO with a known clinical background, 23% were severely immunosuppressed and 23% were associated with treatment.1

The WHO CC in Melbourne has reported that from 1 January 2010 to 28 February 2010 no isolates have shown resistance to oseltamivir by enzyme inhibition assay (EIA) and two clinical specimens collected in Australia have shown the H275Y mutation known to confer resistance to oseltamivir (Table 4).

Table 4. Neuraminidase resistance testing of Australian pandemic (H1N1) 2009 influenza viruses

  2009 2010
  Viral isolates Clinical specimens Viral isolates Clinical specimens
No. tested
587
276
2
3
EIA Resistant
4
N/A
0
N/A
H275Y mutation
N/A
9
N/A
2

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Seasonal Influenza

The last WHO report on resistance of seasonal influenza strains to oseltamivir was released on 4 June 2009, during the Northern Hemisphere influenza season 2008-2009 and stated that 96% of seasonal influenza A (H1N1) isolates tested from 36 countries worldwide were resistant to oseltamivir.2 Australian oseltamivir resistance testing data on seasonal influenza strains are shown in Table 5.

Table 5. Resistance Testing – Seasonal Influenza - Global

Country
% of H1N1 viruses % of A(H3N2) % of B viruses
Australia (since 1 January 2009 and up to 26 February 2010)
97.2% (36/37) resistant to oseltamivir
0% (0/40) resistant to oseltamivir
0% (0/6) resistant to oseltamivir

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4. International Influenza Surveillance

As at 21 February 2010, the WHO Regional Offices reported at least 16,226 deaths associated with pandemic (H1N1) 2009 worldwide. As many countries have stopped counting individual cases, particularly of milder illness, the global case count is likely to be significantly lower than the actual number of cases.3

In the Northern Hemisphere, overall influenza activity continues to decrease in most places. The most active areas of transmission are in parts of South and South East Asia and East and South East Europe. Little activity has been reported in the Southern Hemisphere in 2010 to date.1
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North America

  • In the US during week 7 (up to 20 February 2010), influenza activity remained similar to the previous reporting period. The proportion of outpatient visits for ILI was below the national baseline. Only 4.4% of specimens tested were positive for influenza and all subtyped influenza A viruses reported to CDC were pandemic (H1N1) 2009 influenza viruses.4
  • In Canada during week 7 (up to 20 February 2010), all influenza indicators remained low for this time of the year. The ILI consultation rate was similar to previous weeks and below the expected range for this time of year. Only 0.24% of the specimens tested were positive for influenza A, and the pandemic (H1N1) 2009 strain accounted for 75% of these 5
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Europe

  • During week 7, Bulgaria reported medium influenza activity. All other countries reported low activity. Of the 466 sentinel samples tested, 4.1% were positive for influenza, mostly pandemic (H1N1) 2009 influenza. 6
  • Pandemic influenza activity decreased or remained stable across the UK during week 7 (ending 21 February), except in Wales where it remained stable. The weekly ILI consultation rate decreased in England, Scotland and Northern Ireland, and remained stable in Wales. A slight increase in respiratory synctial virus detections has been observed recently. The main influenza virus circulating in the UK continues to be the pandemic (H1N1) 2009 strain, with few influenza H1 (non-pandemic), H3 and B viruses detected.7
  • In Ireland, influenza activity was at low levels during week 7 (ending 21 February). The sentinel GP ILI consultation rate was 6.1 per 100,000 population during this period, which was similar to the previous reporting period. The highest sentinel GP age-specific ILI consultation rates occurred in the 0-4 year age group. The number of laboratory confirmed cases of pandemic (H1N1) 2009 influenza remained stable at one, and there were no related hospitalisations.8
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5. Data considerations

The information in this report is reliant on the surveillance sources available to the Department of Health and Ageing. As access to sources increase and improve, this report will be refined and additional information will be included.

This report aims to increase awareness of pandemic (H1N1) 2009 and seasonal influenza in Australia by providing an analysis of the various surveillance data sources throughout Australia. While every care has been taken in preparing this report, the Commonwealth does not accept liability for any injury or loss or damage arising from the use of, or reliance upon, the content of the report. Delays in the reporting of data may cause data to change retrospectively. For further details about information contained in this report please contact the Influenza Team through flu@health.gov.au

On 17 June 2009 Australia commenced the transition to a new response phase called PROTECT, in which laboratory testing is directed towards people with moderate or severe illness; those more vulnerable to severe illness; and those in institutional settings. This means that the number of confirmed cases does not reflect how many people in the community have acquired pandemic (H1N1) 2009 infection.

NetEpi

All jurisdictions except QLD are reporting pandemic (H1N1) 2009 cases using NetEpi, a web-based outbreak case reporting system. Data from jurisdictional systems are being imported into NetEpi by VIC, NSW, WA, TAS and SA, and the remainder are entering directly into NetEpi. QLD ceased reporting hospitalisations into NetEpi on 6 July 2009.

Analyses of Australian cases are based on clinical onset date, if this information is available. Where an onset date is not available, notification date has been used. Victoria uses a calculated onset date which is the earliest available date calculated from specimen date, onset date, notification date or detection date. This assumption was made for all calculations and data on which the figures are based.

National Notifiable Diseases Surveillance System (NNDSS)

NNDSS comprises of notifications from jurisdictions of laboratory-confirmed influenza cases. Laboratory confirmed influenza is notifiable in all jurisdictions in Australia. Confirmed pandemic (H1N1) 2009 cases are being received from all jurisdictions through NNDSS except for Victoria and New South Wales. NSW is also unable to send seasonal influenza notifications data.

Data Analysis

Analysis of confirmed influenza cases is conducted on combined NetEpi and NNDSS data. Analysis of morbidity (hospitalisations and ICU admissions) and mortality data is conducted on combined NetEpi and QLD hospitalisation data.

Laboratory Surveillance data

Laboratory testing data are extracted from the ‘NSW Influenza Report,’ and the ‘The 2009 Victorian Influenza Vaccine Effectiveness Audit Report’ (VIDRL) ‘South Australian Seasonal Influenza Report’. These reports are provided weekly.

WHO Collaborating Centre for Reference & Research on Influenza (WHO CC)

Data are provided weekly to the Surveillance Branch from the WHO CC.

Sentinel General Practice Surveillance

The Australian Sentinel Practices Research Network (ASPREN) has Sentinel GPs who report influenza-like-illness (ILI) presentation rates in NSW, SA, ACT, VIC, QLD, TAS and WA. As jurisdictions joined ASPREN at different times and the number of GPs reporting has changed over time, the representativeness of ASPREN data in 2009 may be different from that of previous years. ASPREN data are sent to the Surveillance Branch on a weekly basis. Northern Territory GP surveillance data are sent to the Surveillance Branch on a weekly basis. VIDRL influenza surveillance data are sent to the Surveillance Branch on a weekly basis.

Further information on Sentinel GPs’ Influenza Surveillance and ASPREN activities are available at Further information on Sentinel GPs’ Influenza Surveillance and ASPREN activities are available at www.dmac.adelaide.edu.au/aspren
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Sentinel Emergency Department (ED) data

WA - ED surveillance data are extracted from the ‘Virus Watch’ Report. This report is provided weekly. The Western Australia Influenza Surveillance Program collects data from 8 Perth Emergency Departments (EDs).
NSW - ED surveillance data are extracted from the ‘Influenza Monthly Epidemiology Report, NSW’. This report is provided monthly. The New South Wales Influenza Surveillance Program collects data from 49 EDs across New South Wales.

Absenteeism

A national organisation provides data on the number of employees who have been on sick leave for a continuous period of more than three days. These data are not influenza or ILI specific and absenteeism may be a result of other illnesses.

National Health Call Centre Network

A national organisation provides call centre data for calls relating to ILI or influenza. Data are provided daily and are collated weekly and have been presented in this report to show the pattern of calls to this Call Centre over the 2009 season.

FluTracking

FluTracking is a project of the University of Newcastle, the Hunter New England Area Health Service and the Hunter Medical Research Institute. FluTracking is an online health surveillance system to detect epidemics of influenza. It involves participants from around Australia completing a simple online weekly survey, which collects data on the rate of ILI symptoms in communities.

Data have been provided weekly and have been presented in this report to show the pattern of self reported ILI in the community over the 2009 season.

Further information on FluTracking is available at www.flutracking.net/index.html

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6. References

  1. WHO Pandemic (H1N1) 2009 - Update 89 & Virological Surveillance Weekly Update. Available from http://www.who.int/csr/don/en/ Accessed 2 March 2010.
  2. WHO Influenza A virus resistance to oseltamivir and other antiviral medicines, 4 June 2009. Available from: http://www.who.int/csr/disease/influenza/2008-9nhemisummaryreport/en/index.html Accessed 4 February 2010.
  3. WHO Pandemic (H1N1) 2009 - Update 89 & Virological Surveillance Weekly Update. Available from http://www.who.int/csr/don/en/ Accessed 4 March 2010.
  4. CDC FluView Weekly report, Week 7 ending 20 February 2010. Available from: http://www.cdc.gov/flu/weekly/ Accessed 4 March 2010.
  5. Canada FluWatch Weekly report, week 7 ending 20 February 2010. Available from: http://www.phac-aspc.gc.ca/fluwatch/09-10/index-eng.php Accessed 4 March 2010.
  6. ECDC pandemic update. Available from: http://ecdc.europa.eu/en/activities/surveillance/EISN/Pages/EISN_Bulletin.aspx Accessed 4 March 2010.
  7. HPA weekly pandemic flu media update. Week 8, ending 25 February 2010. Available from: http://www.hpa.org.uk/web/HPAweb&Page&HPAwebAutoListName/Page/1243928258560 Accessed 4 March 2010.
  8. Influenza Surveillance in Ireland - Weekly Update. Influenza Week 7, ending 21 February 2010. Available from: http://www.ndsc.ie/hpsc/A-Z/Respiratory/Influenza/SeasonalInfluenza/InfluenzaSurveillanceReports/20092010Season/File,4168,en.pdf Accessed 4 March 2010.