Report No. 31A print friendly version of this report is available as a PDF (149 KB)
Week ending 11 December 2009
Key IndicatorsThe counting of every case of pandemic influenza is not 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/NNDSS; Sentinel syndromic surveillance systems GP Sentinel ILI Surveillance; and ED presentations of ILI at sentinel hospitals (NSW and WA). Laboratory data are used to determine the proportion of influenza and pandemic (H1N1) 2009 circulating in the community.|
|How severe is the disease, and is severity changing?||Indicated by: number of hospitalisations, ICU admissions and deaths|
|Is the virus changing?||Indicated by: emergence of drug resistance or gene drift/shift from laboratory surveillance.|
This is the last weekly Australian Influenza Surveillance Report produced in 2009. The next report will be available in mid January 2010.
The Department of Health and Ageing acknowledges and greatly appreciates the providers of the many sources of data used to collate this report and to inform public health decisions regarding influenza.
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Is the situation changing?As at 11 December 2009:
- Influenza-like illness (ILI) presentation rates to General Practitioners at a national level were below the baseline levels reached at the end of the 2007 and 2008 influenza seasons. Rates remained stable in most jurisdictions with ILI rates reaching backgrounds levels in most jurisdictions.
- ILI presentations to emergency departments (EDs) remained steady, and slightly above background levels.
- FluTracking surveillance for the week ending 6 December 2009 indicated that ILI activity remained at low levels in all participating jurisdictions.
- Enquiries to the National Health Call Centre Network (NHCCN) regarding ILI continued to drop and were at low levels.
- Absenteeism rates remained similar to levels seen at the same time in 2007.
How severe is the disease?a
Is the virus changing?
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International influenza surveillance
a. Note that the while the analysis of severity is on-going, updates are only reported every four weeks unless there are significant changes detected. With the current low levels of pandemic (H1N1) 2009 activity in Australia it is anticipated that the indicators of pandemic severity will not vary significantly.
1. Influenza activity in Australia
Laboratory Confirmed CasesThere have been 5 new laboratory confirmed pandemic (H1N1) 2009 notifications in reporting week 50 (ending 11 December 2009), with 5 jurisdictions reporting no new notifications. As of 11 December 2009 there were 37,484 confirmed cases of pandemic (H1N1) 2009 in Australia, including 191 pandemic influenza-associated deaths.
Figure 1. Laboratory confirmed cases of pandemic (H1N1) 2009 in Australia, to 11 December 2009 by jurisdiction
Source: NetEPI database
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Figure 2. Influenza activity in Australia, by reporting week, years 2007, 2008 and 2009*
* Data on pandemic (H1N1) 2009 cases is extracted from NetEPI; data on seasonal influenza is extracted from NNDSS.
Sources: NNDSS and NetEPI databases
Sentinel General Practice SurveillanceCombined data available from the Australian Sentinel Practices Research Network (ASPREN), the Northern Territory GP surveillance system and VIDRL, up until 6 December 2009, show that nationally, influenza like Illness (ILI) consultation rates slightly increased this reporting period, remaining below levels seen at the end of the 2007 and 2008 seasons (Figure 3).
In the last week, the presentation rate to sentinel GPs in Australia was approximately 4 cases per 1,000 patients seen.
b. As the counting of every case is no longer feasible in the PROTECT phase, influenza activity, including Influenza Like Illness (ILI) activity in the community is instead monitored by surveillance systems including: GP Sentinel ILI surveillance; Emergency Department presentations of ILI at sentinel hospitals (NSW and WA); and Absenteeism rates. Laboratory data are used to determine the proportion of pandemic (H1N1) 2009 circulating in the community.
Figure 3. Weekly rate of ILI reported from GP ILI surveillance systems from 2007 to 6 December 2009*
* Delays in the reporting of data may cause data to change retrospectively. As data from the NT and the VIDRL surveillance systems are combined with ASPREN data, rates may not be directly comparable across 2007, 2008 and 2009.
SOURCE: ASPREN, NT, VIDRL
Further analysis of the ILI data during this period indicates that levels remained stable in all jurisdictions; with ILI rates reaching backgrounds levels in most jurisdictions (Figure 4).
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Figure 4. Weekly rate of ILI reported from ASPREN, VIDRL and NT by State from January 2009 to 6 December 2009*
*Care should be taken when interpreting graphs due to lags in reporting in some instances and small numbers being reported from jurisdictions. The last data point may be modified in future reports.
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WA emergency departmentsThe number of ILI presentations reported in Western Australian EDs remained steady during this reporting period and is above levels seen at the same time in 2007 and 2008 (Figure 5).
Figure 5. Number of Emergency Department presentations due to ILI in Western Australia from 1 January 2007* to 6 December 2009 by week
* In early July 2007 (week 26), several deaths associated with influenza infection were reported in children from Western Australia. The public response to these deaths could account for the sudden increase in ILI presentations to Perth EDs in 2007.
Source: WA ‘Virus Watch’ Report
NSW emergency departmentsIn November 2009, there were 152 presentations to NSW EDs with ILI (Figure 6). This is below levels seen in October 2009 (244 presentations) but higher than in November 2008 (75).
Figure 6. Comparison of weekly ILI presentations to NSW emergency departments, 2003-2009*
*Emergency department data are preliminary and may be updated in later weeks.
Source: NSW Health ‘Influenza Monthly Epidemiology Report’
FlutrackingFlutracking, a national online tool for collecting data on ILI, reported that activity remained at low levels both nationally and at the State level in the week ending 6 December 2009.
National Health Call Centre NetworkThe number of calls related to ILI to the National Health Call Centre Network (NHCCN) remained stable, with 40 calls in the week ending 11 December 2009. At the peak, the NHCCN received approximately 1900 ILI-related calls per week. The number of calls currently being received is low but not yet at pre-pandemic levels (Figure 7).
Figure 7. Number of calls to the National Health Call Centre Network (NHCCN) related to ILI, Australia, 1 January 2009 (Wk1) to 11 December 2009 (Wk49)*
*Data in the most recent week are incomplete and will update retrospectively.
SOURCE: NHCCN data
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Deaths associated with influenza and pneumoniaDeath registration data show that as of 13 November 2009, there were 73 pneumonia or influenza deaths per 1,000 deaths in NSW, which is expected for this time of year.
Figure 8: Rate of deaths classified as influenza and pneumonia as per NSW Registered Death Certificates, 2004-2009
Source: NSW ‘Influenza Monthly Epidemiology Report’
AbsenteeismThe most recent available data indicates that in the week ending 2 December 2009, absenteeism rates nationally remained steady and are at similar levels to those seen at the same time in 2007 (Figure 9).
Figure 9. Rates of absenteeism of greater than 3 days absent, National employer, 1 January 2007 to 2 December 2009, by week
SOURCE: Absenteeism data (Employer not disclosed)
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Sentinel Laboratory Surveillance - confirmed influenza notificationsResults from sentinel laboratory surveillance systems continued to show very few samples are being confirmed positive for Influenza A virus, but of those that were positive, nearly all were further subtyped as pandemic (H1N1) 2009 strains (Table 1).
Table 1. Laboratory Respiratory tests that tested positive for influenza A and pandemic (H1N1) 2009
|ASPREN* – national||VIC NIC||WA NIC||NT (reported by WA NIC)|
*ASPREN tests are collected every Tuesday. Results are reported for a rolling fortnight as data changes retrospectively.
From 1 January to 11 December 2009, type A was the predominant seasonal influenza type reported by all jurisdictions. Of the type A notifications for which there was subtyping information in NNDSS, the ratio of seasonal H1N1 to H3N2 was 1:2.3.
2. Overview of pandemic (H1N1) 2009 severity - to 20 November 2009cWhile 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 to provide evidence on the severity of the disease in Australia (Table 2).
Of particular note is the difference in the age distribution of the novel influenza virus to seasonal influenza and the increasing median age as the severity of the disease progresses: 21 years for all confirmed cases; 31 years for hospitalised cases; 40 years for ICU cases; and 48 years for deaths.
The disease has also had a differential impact upon Indigenous Australians, who are ten times more likely to be hospitalised with the disease than non-Indigenous Australians. Pregnant women are also over-represented in the more severe cases with pregnancy being a risk factor in 27% of women aged 15 to 44 years who required hospitalisation for the disease.
Table 2. Summary of severity indicators of pandemic (H1N1) in Australia, to 20 November 2009c
|Confirmed pandemic (H1N1) 2009 cases||Hospitalised cases||ICU cases||Deaths|
|Total number||37,269||13% (4,855/37,269 confirmed cases)||13% (655/4,855 hospitalisations)||190|
|Crude rate per 100,000 population||174.4||22.7||3.1||0.9|
|Median age (years)||21||31||40||48|
|Females||51% (18,968/37,141)||51% (2,468/4,855)||54% (351/655)||44% (84/190)|
|Vulnerable groups (Indigenous, pregnant & individuals with at least 1 co-morbidity)||n/a||51% (2,471/4,855)||74% (483/655)||68% (129/190)|
|Indigenous people~||11% (3,830/34,457)||21% (807/3,928)||20% (100/505)||13% (25/190)|
|Pregnant women*||n/a||27% (280/1,034 hospitalised females aged |
|17% (47/280 hospitalised pregnant women)||4% |
(3/84 female deaths)
|Cases with at least 1 co-morbidity||n/a||49% (2,395/4,855)||70% (459/655)||64% (121/190)|
# 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
Another data source focussing on ICU admissions (ANZICs data) show similar figures to the ones reported above: the median age of confirmed cases admitted to ICU was 43 years; vulnerable groups accounted for 81% of the ICU cases; and 73% of the confirmed cases had at least one co-morbidity.
Of particular interest is the number of confirmed cases who were admitted to ICU with viral pneumonitis (2.0 per 100,000 population) and their young age (median age was 39 years). There were 368 adults (over 16 years of age) hospitalised in ICU with Viral Pneumonitis/Acute Respiratory Distress Syndrome due to influenza A compared with a reported annualized median total of only 57 adults admitted with viral pneumonitis (from any cause) from 2005-081. Of the adults, 86% (316) were aged 25-64 years (ANZICs data).
c Note that the while the analysis of severity is on-going, updates are only reported every four weeks unless there are significant changes detected. With the current low levels of pandemic (H1N1) 2009 activity in Australia it is anticipated that the indicators of pandemic severity will not vary significantly.
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Antigenic characteristics - WHO Collaborating Centre for Reference & Research on Influenza (WHO CC) in MelbourneIn 2009 up to 11 December 2009, 1,518 Australian influenza isolates have been subtyped by the WHO CC (Table 3). Of these, 804 influenza isolates have been antigenically characterized, with 68% confirmed as pandemic A/H1N1 2009 (A/California/7/2009-like).
Table 3. Typing of Influenza isolates from the WHO Collaborating Centre, 1 Jan. – 11 Dec. 2009
|Pandemic (H1N1) 2009||41||64||141||77||181||9||210||381||1104|
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 a random sample of all those in the community hence proportions of pandemic (H1N1) 2009 to seasonal are not representative of the proportions circulating. Early in the pandemic all influenza A untypeable samples were sent to the WHO CC for testing and later many pandemic (H1N1) 2009 positive samples were sent for confirmation, resulting in biases in the data.
In general, seasonal influenza A strains circulating this influenza season are the same as strains in the vaccine, with the A(H3N2) virus drifting. Influenza B strains match more closely with those in the 2009-2010 Northern Hemisphere vaccine and may be drifting.
A number of A(H3N2) viruses similar to the reference virus A/Perth/16/2009 have been isolated in Queensland, Western Australia and New South Wales during the influenza season in Australia. As viruses of this type have also been isolated elsewhere in 2009, an A(H3N2) A/Perth/16/2009-like virus has been recommended for inclusion in the 2010 Australian influenza vaccine.
International updatesThe Global Influenza Surveillance Network (GISN) is monitoring the global circulation of influenza viruses, including pandemic, seasonal and other influenza viruses infecting, or with the potential to infect, humans including seasonal influenza. Globally, since the beginning of the pandemic 19 April to 28 November, the total number of specimens reported positive for influenza viruses by National Influenza Centres was 337,902. Of these, 246,571 (73%) were pandemic H1N1, 8,245 (2.4%) were seasonal A (H1), 23,675 (7%) were A (H3), 53,479 (15.8%) were A (not subtyped) and 5,932 (1.8%) were influenza B. This data should be interpreted with caution as many laboratories are not testing for influenza subtypes during surges in pandemic activity. A mutation of D222G in the amino acid sequence in the haemagglutinin protein of the pandemic virus found in Norway is being monitored by GISN. In addition to Norway, the mutation has also been detected in Brazil, China, Japan, Mexico, Italy, Finland, France, Ukraine, US and Hong Kong since April 2009, in both severe and mild cases.2
Pandemic (H1N1) 2009To 11 December 2009, WHO reported that 102 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.2 Around one third of these cases occurred in patients whose immune systems were severely suppressed by haematological malignancy, aggressive chemotherapy for cancer, or post-transplant treatment.3
The WHO CC in Melbourne has reported that one isolate has shown resistance to oseltamivir by enzyme inhibition assay and ten clinical specimens have shown the H275Y mutation (Table 4).
Table 4. Neuraminidase resistance testing of Australian pandemic (H1N1) 2009 viruses
Seasonal InfluenzaThe 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.4 More recent oseltamivir resistance testing data on seasonal influenza strains from Australia and New Zealand are shown in Table 5.
Table 5. Resistance Testing – Seasonal Influenza - Global
% of H1N1 viruses
% of A(H3N2)
% of B viruses
|Australia (since |
1 January 2009 and up to 13 December 2009)
97.2% (36/37) resistant to oseltamivir
0% (0/40) resistant to oseltamivir
0% (0/6) resistant to oseltamivir
|New Zealand (up to 6 December 2009)5|
100% (53/53) resistant to oseltamivir
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4. International Influenza SurveillancedAs at 6 December 2009, the WHO Regional Offices reported at least 9,596 deaths associated with pandemic (H1N1) 2009 worldwide. Given that countries are no longer required to test and report individual cases, these reports are likely to significantly underestimate the actual number of deaths that have occurred.2
Pandemic influenza activity has passed its peak in North America and in parts of western, northern, and eastern Europe, but activity continues to increase in parts of central and south eastern Europe, as well as in south and east Asia. Influenza transmission remains active in much of western and central Asia and there is evidence of pandemic virus circulation in most regions of Africa.2
North AmericaIn United States and Canada, active influenza virus transmission persists but overall influenza activity continues to decline. However, the overall rate of hospitalization and death in the population is similar to that which was observed in temperate countries of the southern hemisphere during their winter.2
d. When possible, information in this section is collated from reports available within the current reporting period.
Central and South AmericaIn the tropical region of Central and South America and the Caribbean, influenza transmission remains geographically widespread but overall disease activity has been declining in most areas.2
EuropeGeographically widespread transmission of pandemic influenza virus continued to be observed across the continent, with most European countries witnessing medium influenza intensity and only nine reporting high to very high levels. Thirteen countries have reported decreasing rates of influenza-like illness for at least the last two weeks. The proportion of influenza-positive sentinel samples continues to decline, but pandemic influenza A(H1N1) virus still accounts for 99% of all subtyped viruses in sentinel patients.9
AsiaIn Western and Central Asia, influenza virus transmission remains active. ILI activity continues to increase in Kazakhstan and Kyrgyzstan, but may have peaked in Afghanistan, Israel, and Oman. Pandemic influenza virus continues to circulate in Iran, Iraq, Jordan, and in much of the surrounding region.
AfricaLimited data suggest that pandemic H1N1 2009 virus continues to be detected from all parts of the African continent (except South Africa where the winter season has passed). Pandemic H1N1 2009 virus appears to be the predominant influenza virus circulating in northern and eastern Africa.
OceaniaIn the temperate region of the southern hemisphere, sporadic cases of pandemic influenza have been reported in recent weeks but no sustained local transmission has been observed.
ILI consultation rates increased slightly in New Zealand in the week ending 6 December (week 49) to 22.1 per 100,000 population from 20.3 in the previous week. The highest ILI consultation rates have been reported among children and teenagers aged 0 to 19 years.(5)
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6. Data considerationsThe 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 email@example.com
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.
NetEpiAll 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. Victorian cases use 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 AnalysisAnalysis of confirmed cases in 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.
Australian and New Zealand Intensive Care data (ANZICs data)During the initial months of the pandemic (H1N1) 2009, the Australian and New Zealand Intensive Care society, with support from the Commonwealth of Australia Department of Health established a `near real time` registry of patients admitted to Australian ICUs. This tracked and documented the evolution of the pandemic through Australia’s health care system and established the key factors influencing mortality, as well as the need for hospitalisation and mechanical ventilation. Information collected includes demographic data, information on relevant co-morbidities, nature of the clinical syndrome associated with pandemic (H1N1) 2009, provision of information on major therapeutic interventions from which organ failure outcomes can be imputed (intubation, ventilation, Extracorporeal Membrane Oxygenation (ECMO), vasopressor administration, dialysis), vaccination status and vital status at time of ICU discharge and hospital discharge.
Laboratory Surveillance dataLaboratory 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 SurveillanceThe 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.
A new testing protocol introduced through ASPREN requires GPs to test all patients presenting with an ILI on one day of the week. These data should provide a cross section of age, sex and severity of patients who seek GP assistance for ILI. This system is in the early stages of implementation and will be further developed over coming weeks.
Sentinel Emergency Department (ED) dataWA - 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.
AbsenteeismA 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 NetworkA 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.
FluTrackingFluTracking 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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7. References1. Critical Care Services and 2009 H1N1 Influenza in Australia and New Zealand, The New England Journal of Medicine Vol. 361:1925-1934.
2 WHO Pandemic (H1N1) 2009 - Update 78 & Virological Surveillance Weekly Update. Available from http://www.who.int/csr/don/en/. Accessed 15 December 2009.
3 WHO Pandemic (H1N1) 2009 briefing note 18 - Oseltamivir resistance in immunocompromised hospital patients. 2 December 2009. Available from: http://www.who.int/csr/disease/swineflu/notes/briefing_20091202/en/index.html. Accessed 9 December 2009.
4 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 15 December 2009.
5 New Zealand Public Health Surveillance, Influenza Weekly Update 49. Available at: http://www.surv.esr.cri.nz/virology/influenza_weekly_update.php. Accessed 15 December 2009.
6 CDC FluView Weekly report, Week 48 ending 5 December 2009. Available from: http://www.cdc.gov/flu/weekly/. Accessed 15 December 2009.
7 Canada FluWatch Weekly report, week ending 5 December 2009 (Week 48). Available from: http://www.phac-aspc.gc.ca/fluwatch/09-10/index-eng.php. Accessed 15 December 2009.
8 Mexico Ministry of Health, Current Epidemic Situation [Influenza], 9 December, 2009. http://portal.salud.gob.mx/descargas/pdf/influenza/situacion_actual_epidemia_091209.pdf. Accessed 15 December 2009.
9 ECDC weekly pandemic update – issue 23, 14 December 2009. Available from: http://ecdc.europa.eu/en/healthtopics/Documents/Forms/AllItems.aspx. Accessed 15 December 2009.
10 HPA weekly pandemic flu media update for week 50, 10 December 2009. Available from: http://www.hpa.org.uk/webw/HPAweb&Page&HPAwebAutoListName/Page/1240732817665?p=1240732817665 Accessed 15 December 2009.
11 Influenza Surveillance in Ireland - Weekly Update. Influenza week 49. Available from: http://www.hpsc.ie/hpsc/A-Z/EmergencyPlanning/AvianPandemicInfluenza/ Accessed 15 December 2009.