Report No. 15A print friendly version of this report is available as a PDF (355 KB)
Week ending 14 October 2011
The Department of Health and Ageing acknowledges the providers of the many sources of data used in this report and greatly appreciates their contribution.
Key IndicatorsInfluenza activity and severity in the community is monitored using the following indicators and surveillance systems:
|Is the situation changing?||Indicated by trends in:
|How severe is the disease, and is severity changing?||Indicated by trends in:
|Is the virus changing?||Indicated by trends in:
- Across all surveillance systems, influenza activity this fortnight has continued to decrease.
- Levels of influenza-like illness (ILI) activity at the community level during 2011 were consistent with previous seasons, excluding 2009.
- During the 2010/11 inter-seasonal period, all jurisdictions reported higher than usual numbers of notifications, especially in the Northern Territory and Queensland. The reason for this unusually high activity is not clear, but do not appear to be due solely to increased testing. During this period, most of the influenza activity was attributed to pandemic (H1N1) 2009 and A(H3N2) infections.
- The main 2011 winter season, commenced and peaked earlier than in previous years and nationally, the majority of virus detections were pandemic (H1N1) 2009, with co-circulation of influenza B. The timing of influenza activity peaks and the distribution of influenza subtypes varied across states and territories.
- At the beginning of the winter season there was a high proportion of influenza B reported, mostly from South Australia, and very little A(H3N2). In recent weeks the proportion of A(H3N2) has continued to increase, with notifications mostly reported from Queensland, Western Australia and the Northern Territory.
- As at 16 October 2011, there have been 25,092 confirmed cases of influenza reported to the National Notifiable Diseases Surveillance System (NNDSS) in 2011. Nationally, weekly notifications for this season peaked in the week ending 5 August 2011 with 1,989 influenza notifications.
- Whilst the peak in notifications was above the peak frequency experienced in previous years, except 2009, assessment of this peak in conjunction with other surveillance systems monitored highlights that this difference in activity was not significant.
- During the season around 84% of influenza related hospitalisations were associated with pandemic (H1N1) 2009 (42%) or influenza A(untyped) (42%). Thirteen per cent of persons hospitalised with influenza were admitted to ICU.
- The WHO has reported that influenza activity in the temperate regions of the northern hemisphere remain low. Influenza activity in the tropical region is active in a few countries. In New Zealand, rates of national ILI consultations continue to remain below baseline activity levels.
- The Australian Influenza Vaccine Committee (AIVC) has agreed to adopt the WHO recommendations for the composition of the 2012 southern hemisphere influenza season vaccine. The recommended viruses are the same as the current 2011 southern hemisphere and the 2011-2012 northern hemisphere vaccine compositions.
- This will be the final Australian Influenza Surveillance Report for 2011, unless unusual activity becomes apparent over the summer months.
1. Influenza activity in Australia
Sentinel General Practice SurveillanceSentinel general practitioner ILI consultation rates have continued to decline. In the week ending 14 October 2011, the national ILI consultation rate to sentinel GPs was 6 cases per 1,000 consultations, down from 9 cases per 1,000 in the previous fortnight (Figure 1). Compared to 2010, ILI consultation rates peaked earlier, however the levels observed were consistent with the 2010 season.
Figure 1. Weekly rate of ILI reported from GP ILI surveillance systems from 1 January 2008 to 16 October 2011*
* Delays in the reporting of data may cause data to change retrospectively. As data from the previous Northern Territory surveillance system was combined with ASPREN and VIDRL surveillance data for 2008 and 2009, rates may not be directly comparable across 2010 and 2011.
SOURCE: ASPREN and VIDRL GP surveillance system1
In the fortnight ending 16 October 2011, specimens were collected from almost two thirds of ASPREN ILI patients. Of these patients, 20 specimens (22%) were positive for influenza, which is a decrease compared to the previous fortnight. Sixteen specimens were typed as influenza type A, and were a mix of pandemic (H1N1) 2009, A(H3N2) and A(untyped); and the remainder (4) were influenza type B. Twenty-eight specimens were positive for other respiratory viruses, with the majority of these being and parainfluenza virus type 3 (9), human metapneumovirus and rhinovirus (6) (Table 1).
Table 1. ASPREN ILI consultations laboratory respiratory viral tests that were positive for influenza or other respiratory virus, 1 January 2011 to 16 October 2011.
(2 to 16 October 2011)
(1 January – 16 October 2011)
|Total specimens tested|
|Total Influenza Positive|
|Pandemic (H1N1) 2009|
|Influenza A untyped|
|Total Positive other Resp. Viruses*|
* Other respiratory viruses include RSV, parainfluenza, adenovirus and rhinovirus.
Western Australia Emergency DepartmentsIn the fortnight ending 16 October 2011, respiratory viral presentations to WA EDs continued to decrease, however presentations remain well above baseline levels. Over this period there were 976 presentations, including 72 admissions (Figure 2). The proportion of presentations admitted to hospital over this period increased to 7.4%, compared to 5.5% in the previous fortnight.
Figure 2. Number of respiratory viral presentations to WA EDs from 1 January 2008 to 16 October 2011, by week
Source: WA ‘Virus Watch’ Repor2
New South Wales Emergency DepartmentsIn the week ending 30 September 2011 the number of patients presenting to NSW EDs with ILI was relatively similar to the previous week and activity was reported as being below the usual range for this time of year (Figure 3). Just over half of the ILI presentations were reported in people aged 25 to 44 and 55 to 64 years (58%). Total admissions from ED to critical care units for ILI and pneumonia decreased this week, and remained within the usual range for this time of year.3 The peak in ED presentations appears to have occurred in the week ending 29 July 2011.
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Figure 3. Rate of influenza-like illness presentations to NSW Emergency Departments between May and October, 2008 to 2011, by week*
Source: NSW Influenza Weekly Epidemiology Report3
*Data missing for weeks 34 and 35
FluTrackingFluTracking, a national online system for collecting data on ILI in the community, noted that in the week ending 16 October 2011 fever and cough was reported by 2.3% of vaccinated participants and 2.4% of unvaccinated participants (Figure 4).4 Fever, cough and absence from normal duties was reported by 1.1% of vaccinated participants and 1.3% of unvaccinated participants. Rates of ILI among FluTracking participants have remained relatively stable this season, compared to previous years (Figure 5).
Up to 16 October 2011, 5,654 out of 10,151 (55.7%) participants reported having received the seasonal vaccine so far. Of the 2,320 participants who identified as working face-to-face with patients, 1,692 (72.9%) have received the vaccine.
Figure 4. Rate of ILI symptoms among Flutracking participants by week, from week ending 8 May 2011 to week ending 16 October 2011.
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Figure 5. Rate of fever and cough among FluTracking participants by week, between May and October, 2007 to 2011.
In regard to Figure 5, FluTracking investigators found that at the community level, peak ILI levels for 2007 were higher than 2009. This finding was consistent with other surveillance systems measuring ILI at the community level, with ASPREN showing similar levels of peak ILI in 2007 and 2009; Google flu trends showed higher levels of ILI at the peak in 2007 as compared to 2009; and workplace absenteeism showed slightly higher peak levels of ILI in 2007 than 2009. FluTracking data are consistent with NSW mortality data for influenza and pneumonia. Although laboratory data and emergency department (ED) data showed higher peak levels of influenza in 2009 then 2007, FluTracking found that the laboratory data were biased by increased testing in 2009 and ED data were biased by increased health seeking behaviour during the pandemic. See: http://wwwnc.cdc.gov/eid/article/16/12/10-0935-f1.htm
National Health Call Centre NetworkThe number of ILI related calls to the National Health Call Centre Network (NHCCN) continued to decrease this fortnight. The percentage of total calls also continued to decrease, and in the week ending 16 October 2011 5.6% of calls to the NHCCN were ILI related, which is slightly less than the same period in 2010 (Figure 6). This year, the percentage of ILI related calls to the NHCCN peaked at 10.3% at the beginning of July and was only slightly higher than the peak experienced in 2010 (9.0%)
Figure 6. Number of calls to the NHCCN related to ILI and percentage of total calls, Australia, 1 January 2010 to 16 October 2011
Note: National data do not include Queensland and Victoria
Source: NHCCN data
Laboratory Confirmed Influenza
Laboratory Confirmed Cases Notified to Health DepartmentsDuring this reporting period there were 979 laboratory confirmed influenza notifications reported to the NNDSS. Of these notifications, there were 358 in Qld, 196 in Vic, 166 in SA, 148 in WA, 75 in NSW, 26 in the NT, 8 in TAS, and 2 in the ACT (Figure 7). A weekly breakdown of trends by state and territory highlights that notifications have continued to be highest in Queensland. Notifications are continuing to decrease across all states and territories (Figure 9).
Figure 7. Laboratory confirmed cases of influenza in Australia, 1 January to 14 October 2011, by state, by week.
Source: NNDSS 2011
Up to 30 September, there have been 25,092 laboratory confirmed notifications of influenza diagnosed during 2011 (Figure 8). Of these notifications, there have been 10,129 notified in Qld, 5,047 in NSW, 4,398 in SA, 2,829 in Vic, 1,557 in WA, 563 in the NT, 334 in Tas and 235 in the ACT. Nationally, weekly notifications for this season have peaked. This season’s notifications peaked in the week ending 5 August 2011 with 1,989 influenza notifications, and were above the peak frequency experienced in previous years, except 2009. Over the summer months, all jurisdictions reported higher than usual numbers of notifications, especially in the Northern Territory and Queensland. The reason for this unusually high activity is not clear, but do not appear to be due solely to increased testing.
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Figure 8. Laboratory confirmed cases of influenza in Australia, 1 January 2005 to 14 October 2011
Source: NNDSS 2011
Figure 9. State breakdowns of laboratory confirmed cases of influenza, 1 January to 14 October 2011, by week
Source: NNDSS 2011
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Of the 979 influenza notifications reported to the NNDSS this reporting period, 376 were influenza A (575 were influenza A (untyped), 141 were A(H3N2) and 79 were pandemic (H1N1) 2009), 175 were influenza B, 9 notifications were reported as untyped (Figure 10).
Nationally, compared to the beginning of the winter season, the proportion of A(H3N2) circulating has continued to increase, with notifications mostly being reported from Queensland, Western Australia and the Northern Territory. In Tasmania, New South Wales, the Northern Territory and Queensland influenza B represents around a quarter of their notifications.
So far in 2011, 18,006 (72%) cases were reported as influenza A (37% influenza A (untyped), 28% pandemic (H1N1) 2009 and 7% A(H3N2)) and 6,869 (27%) were influenza B. A further 75 (<1%) were influenza type A&B and 142 (<1%) were untyped (Figure 10).
Note: Northern Territory sub-typing results reported to the NNDSS as "Influenza A/Not Pandemic" have been counted as influenza A(H3N2) notifications.
Figure 10. Laboratory confirmed cases of influenza in Australia, 1 January 2011 to 14 October 2011, by sub-type and week
Source: NNDSS 2011
Sentinel Laboratory SurveillanceResults from sentinel laboratory surveillance systems for this reporting period show that 12.8% (139/1,083) of the respiratory viral tests conducted over this period were positive for influenza (Table 2). Positive influenza specimens were reported from all sentinel laboratories except the NSW NIC as there was no testing data available for this reporting period. The proportion of A(H3N2) reported through sentinel laboratory surveillance systems has continued to increase this fortnight.
Table 2. Sentinel laboratory respiratory virus testing results, 1 October to 14 October 2011
|NSW NIC*||WA NIC||NT|
(Reported by WA NIC)
(PCR Testing Data)
|Total specimens tested|
|Total Influenza Positive|
|Positive Influenza A|
|Pandemic (H1N1) 2009|
|Influenza A untyped|
|Positive Influenza B|
|Most common respiratory virus detected|
RSV, Parainfluenza, Rhinovirus
* = No data provided for this reporting period
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Since 30 April 2011, a total of 11.5% of specimens have been positive for influenza. A breakdown of subtypes within this positive proportion by fortnight is highlighted in Figure 11.
Figure 11. Proportion of sentinel laboratory* tests positive for influenza, by subtype and fortnight, 30 April to 14 October 2011#
* Tasmanian PCR testing data included from 9 July 2011
# NSW NIC testing data not available for the fortnight ending 14 October 2011
Influenza Complications Alert Network (FluCAN) – Victoria and the Australian Capital TerritoryThe Influenza Complications Alert Network (FluCAN) sentinel hospital system in Victoria, South Australia, Western Australia and the ACT has reported 246 hospitalisations, including 34 ICU admissions, associated with influenza between 1 May and 13 October 2011 (Figure 12). Around 41% of the hospitalisations and 44% of ICU admissions have been associated with pandemic (H1N1) 2009 infection. The mean age of patients hospitalised has been 52.9 years.
Figure 12. Number of influenza hospitalisations at sentinel hospitals, Victoria, South Australia, Western Australia and the ACT, by week and influenza subtype, 1 May to 13 October 2011
Source: FluCAN Sentinel Hospitals
Australian Paediatric SurveillanceThe Australian Paediatric Surveillance Unit (APSU) conducts seasonal surveillance of children aged 15 years and under who are hospitalised with severe complications of influenza. Between 1 July and 18 October 2011, there have been 46 hospitalisations associated with severe influenza complications in children, including 20 ICU admissions. Of the 32 hospitalisations with completed questionnaires, around half of these hospitalisations were associated with pandemic (H1N1) 2009 infection, and 13 were noted as having underlying chronic medical conditions. Note: Hospitalisation numbers may change over time due to case reviews.
Deaths associated with influenza and pneumonia
Nationally Notified Influenza Associated DeathsIn 2011, 14 influenza associated deaths have been notified to the NNDSS, with a median age of 47 years. Ten of these cases were reported as having a pandemic (H1N1) 2009 infection, two with influenza type B and the other case reported as having influenza type A (untyped).
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New South Wales Influenza and Pneumonia Death RegistrationsDeath registration data up to 16 September 2011 showed that there were 1.5 pneumonia or influenza associated deaths per 100,000 population in NSW, which is below the seasonal threshold of 1.7 per 100,000 NSW population for this period (Figure 13).3
Figure 13. Rate of deaths classified as influenza and pneumonia from the NSW Registered Death Certificates, 2006 to 16 September 2011
Source: NSW ‘Influenza Weekly Epidemiology Report’3
Typing and antigenic characterisation
WHO Collaborating Centre for Reference & Research on Influenza (WHO CC) in MelbourneFrom 1 January to 16 October 2011, there were 2,274 Australian influenza isolates subtyped by the WHO CC with almost half of these isolates subtyped as pandemic (H1N1) 2009 (Table 3).
Table 3. Typing of influenza isolates from the WHO Collaborating Centre, from 1 January 2011 to 16 October 2011
|Pandemic (H1N1) 2009|
SOURCE: WHO CC
Please note: There may be up to a month delay on reporting of samples.
Isolates tested by the WHO CC are not necessarily a random sample of all those in the community.
Recent analysis of the low reactor pandemic (H1N1) 2009 strains has shown that about 40% have a particular change in the haemagglutinin sequence, which is known to affect antigenicity and to be associated with adaptation to growth in mammalian cell lines. Other low-reactor pandemic (H1N1) 2009 viruses analysed at the WHO CC in 2011 have been genetically diverse. Overall the data do not point to the emergence of a distinct group of antigenic drift variants.
Antiviral ResistanceThe WHO Collaborating Centre in Melbourne has reported that from 1 January to 16 October 2011, 15 influenza viral isolates (out of 1,857 tested) have shown resistance to the neuraminidase inhibitor oseltamivir by enzyme inhibition assay (EIA). A further 18 specimens, out of a total of 210 tested by pyrosequencing, have shown the H275Y mutation known to confer resistance to oseltamivir. A total of 33 influenza viruses have shown resistance to oseltamivir in 2011, all have been the pandemic (H1N1) 2009 subtype.
The recent increase in oseltamivir resistance in pandemic (H1N1) 2009 influenza isolates predominately occurred in the Hunter New England region of New South Wales between June and August 2011. The cluster consisted of 29 cases, of which 6 were hospitalised and three were pregnant. A further two oseltamivir-resistant pandemic (H1N1) 2009 viruses, sampled in July and August, were also found to belong to the cluster. Both of these cases were detected outside the Hunter New England region with no recent travel history to this region. Only one of the cases reported was treated with oseltamivir prior to their positive test for influenza, however this was case not the earliest known cases in the cluster. All of the viruses are sensitive to zanamivir and have not shown any antigenic changes that would affect their recognition by vaccine-induced antibodies.
2012 Southern Hemisphere VaccineThe Australian Influenza Vaccine Committee (AIVC) met on 5 October 20115, and agreed to adopt the WHO recommendations for the composition of the 2012 southern hemisphere influenza season trivalent flu vaccine. The WHO recommended the following viruses be used:6
- an A/California/7/2009 (H1N1)pdm09-like virus;
- an A/Perth/16/2009 (H3N2)-like virus;
- a B/Brisbane/60/2008-like virus
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3. International Influenza SurveillanceThe WHO7 has reported that as at 21 October 2011 influenza activity in the temperate regions of the northern hemisphere remains low or undetectable. In the tropical zone, influenza activity is active in countries of the Americas (Cuba, Honduras and El Salvador); central Africa (Cameroon); and southern and southeast Asia (Bangladesh, Cambodia, Thailand, Lao People’s Democratic Republic and Vietnam). Influenza transmission in South Africa and South America remains low and the season appears to be largely over.
In New Zealand8, for the week ending 16 October 2011, the national rate of ILI consultations continue to remain below the baseline level of activity, with 6 of the twenty district health boards above the national average weekly consultation rate. During this season, almost half of New Zealand’s influenza viruses were identified as influenza type B, with around a third identified as A(H3N2).
National Influenza Centres in 69 countries have reported that for the period 25 September to 8 October 2011, a total of 1,027 specimens were reported as positive for influenza viruses, 716 (70%) were typed as influenza A and 311 (30%) as influenza B. Of the sub-typed influenza A viruses reported, 30% were pandemic (H1N1) 2009 and 70% were influenza A(H3N2)9. Influenza A(H3N2) was predominant at low levels in some countries of the Americas and Asia, where as influenza B was predominant in parts of Africa. Influenza pandemic (H1N1) 2009 activity declined further in the southern hemisphere.
4. 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 as the season progresses, this report will be updated with the additional information.
This report aims to increase awareness of influenza activity 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 Surveillance Team through email@example.com.
Sentinel General Practice SurveillanceThe sentinel general practice ILI surveillance data between 2008 and 2011 consists of two main general practitioner schemes, the Australian Sentinel Practices Research Network (ASPREN) and a Victorian Infectious Disease Reference Laboratory (VIDRL) coordinated sentinel GP ILI surveillance program. Additionally, between 2008 and 2009 a Northern Territory surveillance scheme also operated, however this scheme has since been incorporated in to the ASPREN scheme. The national case definition for ILI is presentation with fever, cough and fatigue.
The ASPREN currently has sentinel GPs who report ILI presentation rates in NSW, NT, SA, ACT, VIC, QLD, TAS and WA. The VIDRL scheme operates in metropolitan and rural general practice sentinel sites throughout Victoria and also incorporates ILI presentation data from the Melbourne Medical Deputising Service. As jurisdictions joined ASPREN at different times and the number of GPs reporting has changed over time, the representativeness of sentinel general practice ILI surveillance data in 2011 may be different from that of previous years.
ASPREN ILI surveillance data are provided to the Department on a weekly basis throughout the year, whereas data from the VIDRL coordinated sentinel GP ILI surveillance program is provided between May and October each year.
Approximately 30% of all ILI patients presenting to ASPREN sentinel GPs are swabbed for laboratory testing. Please note the results of ASPREN ILI laboratory respiratory viral tests now include Western Australia.
Further information on ASPREN is available at www.dmac.adelaide.edu.au/aspren and information regarding the VIDRL coordinated sentinel GP ILI surveillance program is available at: https://www.victorianflusurveillance.com.au/.
Sentinel Emergency Department DataWestern Australia – Emergency Department ILI surveillance data are extracted from the ‘Virus Watch’ Report. This report is produce weekly. The Western Australia Influenza Surveillance Program collects data from eight Perth emergency departments.
New South Wales – Emergency Department ILI surveillance data are extracted from the ‘Weekly Influenza Report, NSW’. The New South Wales Influenza Surveillance Program collects data from 56 emergency departments across New South Wales.
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.
Further information on FluTracking is available at www.flutracking.net/index.html.
FluTracking investigators found that at the community level, peak ILI levels for 2007 were higher than 2009 This finding was consistent with other surveillance systems measuring ILI at the community level, with ASPREN showing similar levels of peak ILI in 2007 and 2009; Google flu trends showed higher levels of ILI at the peak in 2007 as compared to 2009; and workplace absenteeism showed slightly higher peak levels of ILI in 2007 than 2009. FluTracking data are consistent with NSW mortality data for influenza and pneumonia. Although laboratory data and emergency department (ED) data showed higher peak levels of influenza in 2009 then 2007, FluTracking found that the laboratory data were biased by increased testing in 2009 and ED data were biased by increased health seeking behaviour during the pandemic. See: http://wwwnc.cdc.gov/eid/article/16/12/10-0935-f1.htm
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National Notifiable Diseases Surveillance System (NNDSS)Laboratory confirmed influenza (all types) is notifiable under public health legislation in all jurisdictions in Australia. Confirmed cases of influenza are notified through the NNDSS by all jurisdictions. The national case definition is available at: http://www1.health.gov.au/internet/main/publishing.nsf/Content/cda-surveil-nndss-casedefs-cd_flu.htm.
Analyses of Australian notifications are based on the diagnosis date, which is the earliest of the onset date, specimen date or notification date.
Sentinel Laboratory Surveillance dataLaboratory testing data are provided weekly directly from PathWest (WA), VIDRL (VIC), ICPMR (NSW), and Tasmanian laboratories reporting PCR results. Additionally, approximately 30% of all ILI patients presenting to ASPREN based sentinel GPs are swabbed for laboratory testing. Please note the results of ASPREN ILI laboratory respiratory viral tests now include Western Australia.
Influenza Complications Alert Network (FluCAN)The Influenza Complications Alert Network (FluCAN) sentinel hospital system monitors influenza hospitalisations at the following sites:
- Victoria – Geelong Hospital, Royal Melbourne Hospital, Monash Medical Centre and Alfred Hospital;
- Australian Capital Territory – the Canberra Hospital and Calvary Hospital;
- South Australia – Royal Adelaide Hospital;
- Western Australia – Royal Perth Hospital.
Australian Paediatric Surveillance UnitThe Australian Paediatric Surveillance Unit (APSU) conducts seasonal surveillance of children aged 15 years and under who are hospitalised with severe complications of influenza. Reports are collated on a weekly basis from approximately 1,300 paediatricians and other child health clinicians around Australia. The protocol and case definition is available at:
Deaths associated with influenza and pneumoniaNationally reported influenza associated deaths are notified by jurisdictions to the NNDSS, which is maintained by the Department of Health and Ageing. Notifications of influenza associated deaths are likely to underestimate the true number of influenza associated deaths occurring in the community.
NSW influenza and pneumonia deaths data are collected from the NSW Registry of Births, Deaths and Marriages. Figure 13 is extracted from the ‘Weekly Influenza Report, NSW’. NSW Registered Death Certificates are routinely reviewed for deaths attributed to pneumonia or influenza. While pneumonia has many causes, a well-known indicator of seasonal and pandemic influenza activity is an increase in the number of death certificates that mention pneumonia or influenza as a cause of death. The predicted seasonal baseline estimates the predicted rate of influenza or pneumonia deaths in the absence of influenza epidemics. If deaths exceed the epidemic threshold, then it may be an indication that influenza is beginning to circulate widely.
WHO Collaborating Centre for Reference & Research on Influenza (WHO CC)
Data are provided weekly to the Department from the WHO CC.
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1 The 2011 Victorian Influenza Vaccine Effectiveness Audit Report #41, 16 October 2011. Available from: www.victorianflusurveillance.com.au. Accessed 21 October 2011.
2 WA Virus Watch Report, 16 October 2011. Available from: http://www.public.health.wa.gov.au/cproot/4178/2/20111016_Virus_WAtch.pdf. Accessed 21 October 2011
3 NSW Influenza Weekly Epidemiology Report, 24 to 30 September 2011. Available from: http://www.health.nsw.gov.au/resources/publichealth/infectious/influenza/pdf/week_ending_30092011.pdf, Accessed 12 October 2011.
4 FluTracking Weekly Interim Report #24, 16 October 2011. Available from: http://www1.hnehealth.nsw.gov.au/hneph/HNEPHApplications/FluSurvey/Reports/LatestReport.pdf. Accessed 21 October 2011.
5 Australian Influenza Vaccine Committee (AIVC) recommendations for the composition of influenza vaccine for Australia in 2012. Available from: http://www.tga.gov.au/about/committees-aivc.htm. Accessed 21 October 2011.
6 WHO Recommended composition of influenza virus vaccines for use in the 2012 southern hemisphere influenza season. Available from: http://www.who.int/influenza/vaccines/virus/recommendations/2012south/en/index.html . Accessed 12 October 2011.
7 WHO Influenza Update 145 (21 October 2011). Available from: http://www.who.int/influenza/surveillance_monitoring/updates/latest_update_GIP_surveillance/en/index.html#. Accessed 24 October 2011.
8 New Zealand Influenza Weekly Update, 10 to 16 October 2011. Available from: http://www.surv.esr.cri.nz/virology/influenza_weekly_update.php, Accessed 21 October 2011.
9 WHO Laboratory confirmed data from the Global Influenza Surveillance Network – 21 October 2011. Available from: http://www.who.int/influenza/gisrs_laboratory/updates/summaryreport/en/index.html. Accessed 24 October 2012.