Australian influenza report 2011 - 28 May – 10 June 2011 (#6/11)

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: June 2011

Report No. 6
Week ending 10 June 2011

A print friendly version of this report is available as a PDF (261 KB)

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 Indicators

Influenza activity and severity in the community is monitored using the following indicators and surveillance systems:

Is the situation changing?Indicated by trends in:
  • laboratory confirmed cases reported to the National Notifiable Diseases Surveillance System;
  • GP Sentinel influenza-like illness (ILI) Surveillance;
  • emergency department (ED) presentations for ILI;
  • ILI-related absenteeism and call centre calls: and
  • sentinel laboratory test results.
How severe is the disease, and is severity changing?Indicated by trends in:
  • hospitalisations, ICU admissions and deaths from sentinel systems; and
  • clinical severity in hospitalised cases and ICU admissions.
Is the virus changing?Indicated by trends in:
  • drug resistance; and
  • genetic drift or shift from laboratory surveillance.

Summary

  • Levels of influenza-like illness (ILI) in the community continue to remain low through sentinel general practitioner surveillance systems, however ILI presentations to emergency departments have increased.
  • In recent weeks, notifications have increased most notably in South Australia and Queensland, with some increases also observed in most of the other jurisdictions.
  • During this reporting period there were 574 laboratory confirmed notifications of influenza, with Queensland and South Australia reporting the highest number of notifications. The majority of virus detections have been pandemic (H1N1) 2009, with co-circulation of influenza B. The majority of the South Australian notifications this fortnight have been influenza B (85%).There were no detections of influenza A(H3N2) reported this fortnight.
  • As at 27 May 2011, there have been 4,492 confirmed cases of influenza reported to the National Notifiable Diseases Surveillance System (NNDSS) in 2011, compared with 967 for the same period in 2010.
  • The WHO has reported that worldwide influenza activity is low and activity associated with the northern hemisphere influenza season has finished. Seasonal transmission does not appear to have commenced in most temperate countries of the southern hemisphere.
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1. Influenza activity in Australia

Influenza-Like Illness

Sentinel General Practice Surveillance

In the week ending 5 June 2011, the national ILI consultation rate to sentinel GPs was 7 cases per 1,000 consultations, up from 5 cases per 1,000 consultations last fortnight (Figure 1). The overall trend in ILI rate for 2011 is stable and similar compared to the same time in 2008 and 2010.

Figure 1. Weekly rate of ILI reported from GP ILI surveillance systems from 1 January 2008 to 5 June 2011*
Figure 1. 	Weekly rate of ILI reported from GP ILI surveillance systems from 1 January 2008 to 5 June 2011

* Delays in the reporting of data may cause data to change retrospectively. As data from the VIDRL surveillance system is combined with ASPREN data for 2010 and 2011, rates may not be directly comparable across 2008 and 2009.
SOURCE: ASPREN and VIDRL GP surveillance system1.


Of the ASPREN ILI specimens collected in the fortnight ending 5 June 2011, 7 specimens (8%) were positive for influenza with 3 of those being positive for pandemic (H1N1) 2009, 3 influenza B positive and the other one influenza A untyped. Due to the small number of specimens tested it is difficult to yet determine any general trends in influenza positivity. Twelve specimens were positive for other respiratory viruses, with the majority of these being rhinovirus (8) (Table 1). Please note the results of ASPREN ILI laboratory respiratory viral tests now include Western Australia.

Table 1. ASPREN ILI consultations laboratory respiratory viral tests that were positive for influenza or other respiratory virus, 1 January 2011 to 5 June 2011.
        ASPREN
        (Fortnight 23 May –
        5 June 2011)
        ASPREN
        (YTD 1 Jan – 5 June 2011)
Total specimens tested
57
354
Total Influenza Positive
7
45
Influenza A
4
35
Pandemic (H1N1) 2009
3
24
Seasonal A/H3N2
0
1
Influenza A untyped
1
10
Influenza B
3
10
Total Positive other Resp. Viruses*
12
100

* Other respiratory viruses include RSV, para-influenza, adenovirus and rhinovirus.


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WA Emergency Departments

In the fortnight ending 12 June 2011 there were 871 respiratory viral presentations to WA EDs, including 44 admissions. The number of respiratory viral presentations reported in WA EDs in the first quarter of 2011 has been slightly higher than in previous years. In the past fortnight, the number of presentations has increased above the levels experienced for the same period in 2008 and 2010 (Figure 2).

Figure 2. Number of respiratory viral presentations to WA EDs from 1 January 2008 to 12 June 2011, by week
Figure 2.	Number of respiratory viral presentations to WA EDs from 1 January 2008 to 12 June 2011, by week

Source: WA ‘Virus Watch’ Report2.


NSW Emergency Departments

In the week ending 10 June 2011 the total count of ILI presentations to NSW EDs was 1.3 cases per 1,000 consultations. This is higher than the previous week, but is within the usual range observed in previous years. A higher proportion of presentations were reported in the 15 to 34 year age group (52%).

Pneumonia and ILI admissions to critical care units increased this week, and are slightly above the usual range seen at this time of year. 3

Flutracking

Flutracking, a national online system for collecting data on ILI in the community, reported that in the week ending 5 June 2011 fever and cough was reported by 2.9% of vaccinated participants and 3.9% of unvaccinated participants (Figure 3) 4. Fever, cough and absence from normal duties was reported by 1.5% of vaccinated participants and 1.9% of unvaccinated participants.

Up to 5 June, 6,813 out of 10,495 (64.9%) participants reported having received the seasonal vaccine so far. Of the 2,417 participants who identified as working face-to-face with patients, 1,945 (80.5%) have received the vaccine.

Figure 3. Rate of ILI symptoms among Flutracking participants by week, from week ending 8 May 2011 to week ending 5 June 2011.
Figure 3. 	Rate of ILI symptoms among Flutracking participants by week, from week ending 8 May 2011 to week ending 5 June 2011

Source: FluTracking


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National Health Call Centre Network

The number of ILI-related calls to the National Health Call Centre Network (NHCCN) during this fortnight increased compared to recent weeks. The percentage of total calls also increased slightly, comparable to the same period in 2010 (Figure 4).

Figure 4. Number of calls to the NHCCN related to ILI and percentage of total calls, Australia, 1 January 2010 to 5 June 2011
Figure 4. 	Number of calls to the NHCCN related to ILI and percentage of total calls, Australia, 1 January 2010 to 5 June 2011

Note: National data do not include QLD and VIC
Source: NHCCN data


Laboratory Confirmed Influenza

Sentinel Laboratory Surveillance

Results from sentinel laboratory surveillance systems for this reporting period show that 2.9% (25/849) of the respiratory tests conducted over this period were positive for influenza (Table 2). Positive influenza specimens were only reported from the Tasmanian and NSW sentinel laboratories. Please note that total number of specimens data reported for the Tasmanian sentinel laboratory system only includes one week of data.
      Table 2. Laboratory respiratory tests that tested positive for influenza, 28 May to 10 June 2011*
      NSW NICWA NICNT
      (Reported by WA NIC)
      VIC
      NIC
      TAS
      Laboratories
      Total specimens tested
      314
      243
      2
      241
      49*
      Total Influenza Positive
      7
      0
      0
      0
      18
      Positive Influenza A
      4
      -
      -
      -
      14
      Pandemic (H1N1) 2009
      4
      -
      -
      -
      11
      A/H3N2
      0
      -
      -
      -
      3
      Influenza A untyped
      0
      -
      -
      -
      -
      Positive Influenza B
      3
      -
      -
      -
      4
      The most common respiratory virus detectedRSVRSVRSVPicornavirus-

* Tasmanian total specimens data only available up to 5 June 2011


In 2011 a total of 2.8% of specimens have been positive for influenza, with a breakdown of subtypes within this proportion highlighted in Figure 5.

Figure 5. Proportion of sentinel laboratory tests positive for influenza, by subtype and fortnight, 30 April to 10 June 2011*.
Figure 5. 	Proportion of sentinel laboratory tests positive for influenza, by subtype and fortnight, 30 April to 10 June 2011

* Tasmanian total specimens data only available up to 5 June 2011


Laboratory Confirmed Cases Notified to Health Departments

During this reporting period there were 574 influenza notifications reported to the NNDSS (263 in Qld, 170 in SA, 76 in NSW, 37 in Vic, 10 in WA, 10 in TAS, 7 in the ACT and 1 in the NT) (Figure 7). They included 260 cases of influenza A (untyped), 91 cases of pandemic (H1N1) 2009, 111 of influenza B, 2 of influenza A&B and 4 untyped cases. There were no reports of A/H3N2 this fortnight.

South Australia have continued to report a large increase in notifications over this reporting period with 85% of notifications being influenza B. These accounted for the majority of influenza B reported over this period and are not reflected in the sentinel laboratory data.

There have been 4,492 confirmed cases of influenza diagnosed during 2011 up to 10 June (Figure 6). Of these, 2049 (46%) have been sub-typed as influenza A (untyped), 992 (22%) as pandemic (H1N1) 2009, 573 (13%) as type A/H3N2, and 30 (<1%) were type A&B. A further 819 (18%) have been characterised as influenza type B and 29 (<1%) were untyped.

Please note, Northern Territory sub-typing results reported to the NNDSS as "Influenza A/Not Pandemic" have been counted as influenza A/H3N2 notifications.

Figure 6. Laboratory confirmed cases of influenza in Australia, 1 January 2005 to 10 June 2011
Figure 6. Laboratory confirmed cases of influenza in Australia, 1 January 2005 to 10 June 2011

Source: NNDSS 2011


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As at 10 June 2011, the number of laboratory confirmed cases of influenza in 2011 was 2,070 in Qld, 649 in NSW, 532 in SA, 544 in Vic, 336 in the NT, 232 cases in WA, 71 cases in Tas and 28 cases in the ACT (Figure 6). All jurisdictions have reported higher than usual numbers of notifications over the summer months, especially in the Northern Territory and Queensland. The reason for this unusually high activity earlier in the year is not clear, but it does not appear to be due solely to increased testing.

A breakdown of trends by state and territory, highlights that in recent weeks notifications have increased mostly in South Australia and Queensland, with some increases also observed in most of the other jurisdictions (Figure 8).

Figure 7. Laboratory confirmed cases of influenza in Australia, 1 January to 10 June 2011, by state, by week.
Figure 7.	Laboratory confirmed cases of influenza in Australia, 1 January to 10 June 2011, by state, by week

Figure 8. State breakdowns of laboratory confirmed cases of influenza, 1 January to 10 June 2011, by week

Figure 8. State breakdowns of laboratory confirmed cases of influenza, 1 January to 10 June 2011, by week - ACT
Figure 8. State breakdowns of laboratory confirmed cases of influenza, 1 January to 10 June 2011, by week - NSW
Figure 8. State breakdowns of laboratory confirmed cases of influenza, 1 January to 10 June 2011, by week -
Figure 8. State breakdowns of laboratory confirmed cases of influenza, 1 January to 10 June 2011, by week - QLD
Figure 8. State breakdowns of laboratory confirmed cases of influenza, 1 January to 10 June 2011, by week - SA
Figure 8. State breakdowns of laboratory confirmed cases of influenza, 1 January to 10 June 2011, by week - TAS
Figure 8. State breakdowns of laboratory confirmed cases of influenza, 1 January to 10 June 2011, by week - VIC
Figure 8. State breakdowns of laboratory confirmed cases of influenza, 1 January to 10 June 2011, by week - WA
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Deaths associated with influenza and pneumonia

Nationally notified influenza associated deaths

In 2011, 5 influenza associated deaths have been notified to the NNDSS, with all cases having pandemic (H1N1) 2009.

NSW

Death registration data up to the week ending 20 May 2011, showed that there were 1.3 pneumonia or influenza associated deaths per 100,000 population in NSW, which is below the seasonal threshold of 1.7 per 100,000 population for this period (Figure 9).

Up to the week ending 27 May, there has been one pandemic (H1N1) 2009 associated death with known co-morbidities recorded with NSW public health units.3

Figure 9. Rate of deaths classified as influenza and pneumonia from the NSW Registered Death Certificates, 2006 to 20 May 2011
Figure 9. Rate of deaths classified as influenza and pneumonia from the NSW Registered Death Certificates, 2006 to 20 May 2011

Source: NSW ‘Influenza Weekly Epidemiology Report’3


2. Virology

Typing and antigenic characterisation - WHO Collaborating Centre for Reference & Research on Influenza (WHO CC) in Melbourne

From 1 January to 5 June 2011, there were 474 Australian influenza isolates subtyped by the WHO CC with the majority of these isolates subtyped as pandemic (H1N1) 2009 (50%) or type A/H3N2 (35%) (Table 3).

Table 3. Typing of influenza isolates from the WHO Collaborating Centre, from 1 January 2011 to 5 June 2011
Type/SubtypeACTNSWNTQLDSATASVICWATOTAL
Pandemic (H1N1) 200908281510121722238
A(H3N2)01481050148167
B033222017469
Total0121082780142834474

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.



Antigenic characterisation has shown influenza isolates to be a close match with the composition of the 2011 southern hemisphere influenza vaccine with some viruses showing reduced reactivity, however there has been insufficient testing to date to determine any general trends.

Antiviral Resistance

The WHO Collaborating Centre in Melbourne has reported that from 1 January 2011 to 5 June 2011, one isolate (out of 764 tested) has shown resistance to oseltamivir by enzyme inhibition assay (EIA). A further isolate, out of a total of 7 pandemic H1N1 (2009) tested by pyrosequencing, has shown the H275Y mutation known to confer resistance to oseltamivir.

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3. International Influenza Surveillance

The WHO5 has reported that the influenza season has finished in the temperate countries of the northern hemisphere, with only sporadic influenza virus detections occurring. Transmission in tropical countries of the Americas and sub-Saharan Africa has continued to decline. South Africa has reported an increase in influenza virus detections, primarily influenza A(H1N1)2009, consistent with the start of their winter influenza season. Seasonal transmission does not appear to have started in other temperate countries of the southern hemisphere.

National Influenza Centres in 74 countries have reported that for the period 8 May to 21 May 2011, a total of 721 specimens were reported as positive for influenza viruses, 261 (36.2%) were typed as influenza A and 460 (63.8%) as influenza B. Of the sub-typed influenza A viruses reported, 66% were pandemic (H1N1)2009 and 34% were influenza A(H3N2) 6.

WHO have released a summary review of the northern hemisphere winter influenza season7. The summary review notes that the most commonly detected virus was different in North America, where influenza A(H3N2) and influenza type B co-circulated with pandemic (H1N1)2009, and Europe, where influenza A(H1N1)2009 was by far the most commonly detected virus. Although it was no longer the predominant influenza virus circulating in many parts of the world, pandemic (H1N1) 2009 otherwise behaved much the same way as it had during the pandemic in terms of the age groups most affected and the clinical pattern of illness. More than 90% of viruses detected around the world during the northern hemisphere influenza season were similar antigenically to those found in the seasonal trivalent influenza vaccine. Antiviral resistance in pandemic (H1N1)2009 remained at a very low level.

The WHO has released their recommendation for the antigen composition of 2011-2012 northern hemisphere influenza season trivalent flu vaccine8. It is recommended that vaccines contain the following:
  • an A/California/7/2009 (H1N1)-like virus;
  • an A/Perth/16/2009 (H3N2)-like virus;
  • a B/Brisbane/60/2008-like virus.
This recommended composition is the same as the 2010-2011 Northern Hemisphere and the 2011 Southern Hemisphere vaccine compositions.

4. 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 as the season progresses, this report will be updated with the additional information.

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.

Sentinel General Practice Surveillance

The Australian Sentinel Practices Research Network (ASPREN) has Sentinel GPs who report ILI presentation rates in NSW, NT, 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 2011 may be different from that of previous years. ASPREN data and 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 www.dmac.adelaide.edu.au/aspren.

Sentinel 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 eight Perth EDs.

NSW - ED surveillance data are extracted from the ‘Weekly Influenza Report, NSW’. The New South Wales Influenza Surveillance Program collects data from 56 EDs across New South Wales.

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.

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

Sentinel Laboratory Surveillance data

Laboratory testing data are provided weekly directly from PathWest (WA), VIDRL (VIC), ICPMR (NSW), sentinel Tasmanian laboratories, and ASPREN (national).

National Notifiable Diseases Surveillance System (NNDSS)

Laboratory confirmed influenza (all types) is notifiable in all jurisdictions in Australia. Confirmed cases of influenza are notified through NNDSS by all jurisdictions.

Analyses of Australian cases are based on the diagnosis date, which is the earliest of the onset date, specimen date or notification date.

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

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

Deaths associated with influenza and pneumonia

Nationally reported influenza associated deaths are notified by jurisdictions to the NNDSS which is maintained by the Department of Health and Ageing. However these are an underestimation of the true number of deaths occurring in the community associated with influenza.

NSW influenza and pneumonia deaths data are collected from the NSW Registry of Births, Deaths and Marriages. Figure 6 is extracted from the ‘Weekly Influenza Report, NSW’.

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5. References

1 The 2011 Victorian Influenza Vaccine Effectiveness Audit Report, 5 June 2011. Available from: www.victorianflusurveillance.com.au. Accessed 10 June 2011.
2 WA Virus Watch Report, 12 June 2011. Available from: http://www.public.health.wa.gov.au/3/487/3/virus_watch.pm. Accessed 17 June 2011
3 NSW Influenza Weekly Epidemiology Report, 4 – 10 June 2011. Available from: http://www.health.nsw.gov.au/resources/publichealth/infectious/influenza/pdf/week_ending_10062011.pdf, Accessed 16 June 2011.
4 Flutracking Weekly Interim Report, 5 June 2011. Available from: http://www1.hnehealth.nsw.gov.au/hneph/HNEPHApplications/FluSurvey/Reports/LatestReport.pdf. Accessed 16 June 2011.
5 WHO Weekly Influenza Update 135 (3 June 2011). Available from: http://www.who.int/csr/disease/influenza/latest_update_GIP_surveillance/en/index.html#. Accessed 16 June 2011.
6 WHO Laboratory confirmed data from the Global Influenza Surveillance Network - 6 June 2011. Available from: http://www.who.int/csr/disease/influenza/influenzanetwork/flunet/summaryreport/en/index.html. Accessed 16 June 2011
7 WHO Summary review of the 2010-2011 northern hemisphere winter influenza season. Available from: http://www.who.int/csr/disease/influenza/2010_2011_GIP_surveillance_seasonal_review/en/index.html. Accessed 16 June 2011
8 WHO Recommended composition of influenza virus vaccines for use in the 2011-2012 northern hemisphere influenza season. Available from: http://www.who.int/csr/disease/influenza/recommendations_2011_12north/en/index.html. Accessed 3 June 2011.