Australian influenza report 2009 - 28 November to 4 December 2009 (#30/09)

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 end of season report is also published in Communicable Diseases Intelligence.

Page last updated: 14 December 2009

Report No. 30
Week ending 9 December 2009

A print friendly version of this report is available as a PDF (203 KB)

Disclaimer
This report aims to increase awareness of 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



Key Indicators

The counting of every case of pandemic influenza is no longer feasible in the PROTECT phase. Influenza activity and severity in 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.


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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.

Key items

  • As at 4 December 2009, there had been 37,462 confirmed cases of pandemic (H1N1) 2009 and 191 deaths reported in Australia.
  • As at 29 November 2009, the WHO Regional Offices reported at least 8,768 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.
  • In the temperate zone of the northern hemisphere, the early arriving winter influenza season continues to intensify across central Europe and in parts of central, eastern, and southern Asia. Disease activity has peaked and is declining in North America and has either recently peaked or is currently peaking in much of western and northern Europe.
  • As at 4 December 2009, WHO reported that 96 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. 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.

    Summary

    Is the situation changing?

    As at 4 December 2009:
  • There were 37,462 confirmed cases of pandemic (H1N1) 2009 in Australia.
  • There have been 7 new laboratory confirmed pandemic (H1N1) 2009 notifications in reporting week 49 (ending 4 December 2009), with 5 jurisdictions reporting no new notifications.
  • There have been a total of 191 pandemic influenza-associated deaths.
  • National influenza activity continued to decrease.
      • 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 although some reported rates were slightly above background levels.
      • ILI presentations to emergency departments (EDs) remained steady, and slightly background levels.
      • FluTracking surveillance for the week ending 22 November 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 and 2008.

    The number of respiratory tests positive for influenza A remains low, with all being subtyped as pandemic (H1N1) 2009. Of the seasonal influenza A notifications, influenza A/H3N2 remains the predominant strain reported by most jurisdictions.
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    How severe is the disease?a

  • Analysis of data from NetEpi indicated that the number of people with pandemic (H1N1) 2009 requiring hospitalisation continued to decrease. Of the people who had been hospitalised, 13% were admitted to Intensive Care Units. Of the hospitalisations for which Indigenous status is known, 21% have been Indigenous Australians. Pregnant women represented 27% of all hospitalisations for pandemic (H1N1) 2009 of women aged between 15 and 44 years. 13% of the fatal cases associated with pandemic (H1N1) 2009 were Indigenous Australians

    Is the virus changing?

  • In Australia, one of the 498 pandemic (H1N1) 2009 viral isolates tested by NA enzyme inhibition assay was resistant to oseltamivir, and the H275Y resistance mutation was found in 10 of 272 clinical specimens tested.
  • To date, the WHO has received formal notification of 96 cases of oseltamivir resistance pandemic (H1N1) 2009 viruses worldwide.

    International influenza surveillance

  • The number of human cases of pandemic (H1N1) 2009 continues to increase in many countries. As at 29 November 2009, the WHO reported at least 8,768 deaths associated with pandemic (H1N1) 2009 worldwide.
  • In the temperate zone of the northern hemisphere, the early arriving winter influenza season continues to intensify across central Europe and in parts of central, eastern, and southern Asia. Disease activity has peaked and is declining in North America and has either recently peaked or is currently peaking in much of western and northern Europe.

    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.</p>]
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    1. Influenza activity in Australia

    Laboratory confirmed cases

    There have been 7 new laboratory confirmed pandemic (H1N1) 2009 notifications in reporting week 49 (ending 4 December 2009), with 5 jurisdictions reporting no new notifications. As of 4 December 2009 there were 37,462 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 4 December 2009, by jurisdiction

    Figure 1. Laboratory confirmed cases of pandemic (H1N1) 2009 in Australia, to 4 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*

    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 the NNDSS.
    Sources: NNDSS and NetEPI databases


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    Influenza-Like Illnessb

    Sentinel General Practice Surveillance

    Combined data available from the Australian Sentinel Practices Research Network (ASPREN), the Northern Territory GP surveillance system and VIDRL, up until 29 November 2009, show that nationally, influenza like Illness (ILI) consultation rates declined this reporting period and were 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 3 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 29 November 2009*

    Figure 3. Weekly rate of ILI reported from GP ILI surveillance systems from 2007 to 29 November 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


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    Further analysis of the ILI data during this period indicates that levels remained stable or decreased in most jurisdictions; however this is above background levels in some jurisdictions (Figure 4).

    Figure 4. Weekly rate of ILI reported from ASPREN, VIDRL and NT by State from January 2009 to 29 November 2009*

    Figure 4. Weekly rate of ILI reported from ASPREN, VIDRL and NT by State from January 2009 to 29 November 2009 victoria

    SOURCE: ASPREN (VIC) & VIDRL


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    Figure 4. Weekly rate of ILI reported from ASPREN, VIDRL and NT by State from January 2009 to 29 November 2009 australian capital territory
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    Figure 4. Weekly rate of ILI reported from ASPREN, VIDRL and NT by State from January 2009 to 29 November 2009 western australia

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    Figure 4. Weekly rate of ILI reported from ASPREN, VIDRL and NT by State from January 2009 to 29 November 2009 tasmania

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    Figure 4. Weekly rate of ILI reported from ASPREN, VIDRL and NT by State from January 2009 to 29 November 2009 queensland

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    Figure 4. Weekly rate of ILI reported from ASPREN, VIDRL and NT by State from January 2009 to 29 November 2009 south australia

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    Figure 4. Weekly rate of ILI reported from ASPREN, VIDRL and NT by State from January 2009 to 29 November 2009 northern territory

    SOURCE: NT Surveillance


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    Figure 4. Weekly rate of ILI reported from ASPREN, VIDRL and NT by State from January 2009 to 29 November 2009 new south wales


    *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 departments

    The number of ILI presentations reported in Western Australian EDs has decreased during this reporting period and is slightly 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 29 November 2009 by week

    Figure 5. Number of Emergency Department presentations due to ILI in Western Australia from 1 January 2007* to 29 November 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


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    NSW emergency departments

    In 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*

    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 ‘NSW Influenza Surveillance Report’



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    Flutracking

    Flutracking, a national online tool for collecting data on ILI, reported that activity remained at low levels nationally and in the four States with sufficient data for reporting in the week ending 22 November 2009 (Figure 7).

    Figure 7. Rate of ILI symptoms and absence from regular duties among Flutracking participants by week, from week ending 3 May 2009 to week ending 22 November 2009

    Figure 7. Rate of ILI symptoms and absence from regular duties among Flutracking participants by week, from week ending 3 May 2009 to week ending 22 November 2009

    Source: Flutracking Interim Weekly Report


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    National Health Call Centre Network</h3>]The number of calls related to ILI to the National Health Call Centre Network (NHCCN) remained stable, with 43 calls in the week ending 4 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 8).

    Figure 8. Number of calls to the National Health Call Centre Network (NHCCN) related to ILI, Australia, 1 January 2009 (Wk1) to 4 December 2009 (Wk49)*

    Figure 8. Number of calls to the National Health Call Centre Network (NHCCN) related to ILI, Australia, 1 January 2009 (Wk1) to 4 December 2009

    *Data in the most recent week are incomplete and will update retrospectively.
    SOURCE: NHCCN data




    Absenteeism

    The most recent available data indicates that in the week ending 25 November 2009, absenteeism rates nationally remained at similar levels to those seen at the same time in 2007 and 2008 (Figure 9).

    Figure 9. Rates of absenteeism of greater than 3 days absent, National employer, 1 January 2007 to 25 November 2009, by week.



      Figure 9. Rates of absenteeism of greater than 3 days absent, National employer, 1 January 2007 to 25 November 2009, by week



      SOURCE: Absenteeism data (Employer not disclosed)


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      Sentinel Laboratory Surveillance - confirmed influenza notifications


      Results 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, 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

      Latest report ASPREN* – national VIC NIC WA NIC NT (reported by WA NIC)
      Number of specimens tested
      5
      89
      132
      (at 4/12)
      132
      (at 4/12)
      Number tested which were Influenza A
      0
      1
      5
      1
      Number tested which were pandemic (H1N1) 2009
      0
      1
      5
      1
      Previous report
      Number of specimens tested
      4
      n/a
      120
      (at 27/11)
      120
      (at 27/11)
      Number tested which were Influenza A
      0
      3
      2
      Number tested which were pandemic (H1N1) 2009
      0
      2
      2


      *ASPREN tests are collected every Tuesday. Results are reported for a rolling fortnight as data changes retrospectively.{</p>]

      From 1 January to 4 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.
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      2. Overview of pandemic (H1N1) 2009 severity - to 20 November 2009c



      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 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
      15-44 years)
      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



      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.



      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 2005-08 (1).
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      3. Virology

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

      In 2009 up to 4 December 2009, 1,517 Australian influenza isolates have been subtyped by the WHO CC (Table 3). Of these, 745 influenza isolates have been antigenically characterized, with 66% confirmed as pandemic A/H1N1 2009 (A/California/7/2009-like).

      Table 3. Typing of Influenza isolates from the WHO Collaborating Centre, 1 Jan. – 27 Nov. 2009

      Antigenic characterization
      ACT NSW NT QLD SA TAS VIC WA TOTAL
      A(H1N1)
      2
      25
      0
      29
      21
      1
      11
      27
      116
      Pandemic (H1N1) 2009
      41
      64
      141
      77
      181
      9
      209
      381
      1103
      A(H3)
      16
      95
      8
      41
      2
      8
      39
      68
      277
      B
      0
      8
      0
      1
      0
      0
      4
      8
      21
      Total
      59
      192
      149
      148
      204
      18
      263
      484
      1517


      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.
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      International updates

      The 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 21 November, the total number of specimens reported positive for influenza viruses by National Influenza Centres was 309,204. Of these, 220,641 (71.4%) were pandemic H1N1, 8130 (2.6%) were seasonal A (H1), 23,531 (7.6%) were A (H3), 51,071 (16.5%) were A (not subtyped) and 5831 (1.9%) 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 of the haemagglutinin protein of the pandemic virus found in Norway is being monitored by GISN. In addition to Norway, the mutation has also been observed in Brazil, China, Chinese Taipei, Finland, France, Italy, Japan, Mexico, Spain, Ukraine, and USA, in both severe and mild cases. (2)
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      Antiviral Resistance

      Pandemic (H1N1) 2009

      To 4 December 2009, WHO reported that 96 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)

      On 2 December, WHO reported on two recent clusters of patients infected with oseltamivir resistant pandemic (H1N1) 2009 viruses. Both clusters, detected in Wales (UK) and North Carolina (USA), occurred in a single ward in a hospital, and involved patients whose immune systems were severely compromised or suppressed. Transmission of resistant virus from one patient to another is suspected in both outbreaks. All of the resistant viruses carried the same H275Y mutation, indicating resistance to oseltamivir but susceptibility to the second antiviral drug, zanamivir. WHO experts have made modified treatment recommendations for severely immunocompromised patients with influenza.(3) This raises the possibility that widespread resistance will render the anti-viral drug, oseltamivir, less useful in combating the pandemic (H1N1) 2009 virus. Thus, the pandemic (H1N1) 2009 vaccine, instead of antivirals, should be used for prevention as it becomes available.

      The WHOCC 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

      Description
      No. tested EIA Resistant H275Y mutation
      Viral isolates
      498
      1
      -
      Clinical specimens
      272
      -
      10

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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. (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

      Country
      % of H1N1 viruses % of A(H3N2) % of B viruses
      Australia (since
      1 January 2009 and up to 6 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 22 November 2009) (5)
      100% (53/53) resistant to oseltamivir
      n/a
      n/a


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      4. International Influenza Surveillanced

      As at 29 November 2009, the WHO Regional Offices reported at least 8,768 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)

      In the temperate zone of the northern hemisphere, the early arriving winter influenza season continues to intensify across central Europe and in parts of central, eastern, and southern Asia. Disease activity has peaked and is declining in North America and has either recently peaked or is currently peaking in much of western and northern Europe.

      When possible, information in this section is collated from reports available within the current reporting period.


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      North America

      In both Canada and the United States, influenza virus circulation remains active and geographically widespread. However, disease activity appears to have peaked in past 3 to 4 weeks.

      The US reported a slight overall decrease in influenza activity during week 47 (week ending 28 November 2009). The proportion of outpatient visits for ILI decreased from 4.3% the previous week to 3.7% in week 46, which is still above the national baseline of 2.3%, and 8 of the 10 regions reported ILI above region-specific baseline levels. Cumulative rates of hospitalizations for the current influenza season have exceeded rates seen in recent seasons among all age groups except those aged ≥ 65. The proportion of deaths attributed to pneumonia and influenza was above the epidemic threshold for the ninth consecutive week. Over 99% of all subtyped influenza A viruses being reported to CDC were 2009 influenza A (H1N1) viruses. (6 )

      In Canada, all influenza indicators continued to decrease in week 47 (ending 28 November 2009) compared to the previous week. The pandemic (H1N1) 2009 strain accounted for nearly 100% of the positive influenza A subtyped specimens. The intensity of Pandemic (H1N1) 2009 in the population was moderately high, with a decreased in hospitalizations, ICU admissions and deaths in week 47. The proportion of severe cases (ICU admissions and deaths) among all hospitalized cases was lower in the second wave than in the first wave. (7)

      In Mexico as at 2 December 2009, confirmed cases of pandemic (H1N1) 2009 (66,070) and related deaths (671) continue to increase. (8)

      Central and South America

      In the tropical zone of Central and South America and the Caribbean, influenza transmission remains geographically widespread but overall disease activity has been declining except for focal areas of increasing activity in Jamaica, Venezuela, and Ecuador.(2)
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      Europe

      In Europe, widespread and intense transmission of pandemic influenza virus continued to be observed across most of the continent, with all reporting countries still experiencing medium to very hight influenza intensity. Over 99% of subtyped influenza A viruses in Europe were pandemic H1N1 2009. The cumulative reported deaths since the beginning of the pandemic in Europe has totalled 1,066.(9)

      In western and northern Europe the peak of disease activity has passed in Belgium, Iceland, Ireland, Netherlands, Norway and parts of the United Kingdom (Northern Ireland, Wales); activity may be peaking or plateauing in Spain, Portugal, Italy, Sweden and Denmark. Influenza activity continues to increase in much of Central Europe in the region between the Baltic and Balkan countries and from Germany to Romania. In Eastern Europe, recent peaks or plateaus in disease activity have also been observed in Ukraine, Belarus, Bulgaria and the Republic of Moldova. In the Russian Federation, influenza activity remains active and intense in some regions, with an overall increasing trend. A moderate impact on the healthcare system has been reported in parts of Northern and Eastern Europe.(2)

      In the UK, the weekly ILI consultation rates in week 49 (ending 3 December) decreased slightly in England and Scotland and increased slightly in Wales and Northern Ireland. HPA modelling gives an estimate of 22,000 new cases in England in week 49. The estimated number of new cases has decreased in most regions and age groups. 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. The majority of pandemic influenza cases continue to be mild. The cumulative number of deaths reported due to pandemic (H1N1) 2009 in the UK is 265. The hospitalisation rates have increased in the under 5-year age group, but have decreased in most other age groups recently. (10)

      In Ireland, influenza activity continued to decrease during week 48 (ending 29 November), but remains at higher levels than those recorded in previous seasons. The sentinel GP ILI consultation rate was 93.6 per 100,000 population in week 48, a decrease compared to 126.9 reported during week 47. 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, hospitalised cases and ICU admissions decreased compared the previous week. Pandemic (H1N1) 2009 was the only influenza virus circulating in week 48. (11)
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      Asia

      In Western and Central Asia, influenza transmission remains active. Disease activity continues to increase in Kazakhstan, Kyrgyzstan, Uzbekistan, Iran and Iraq, while activity may have peaked in Israel, Jordan, and Afghanistan.

      In East Asia, increasing ILI or respiratory disease activity has been reported in Southern China and Japan. A recent decline in activity has been observed in Northern China.

      In South and Southeast Asia, influenza activity continues to increase in the north-western parts of India, Nepal, Sri Lanka, and Cambodia, while activity in the rest of region remain low.

      Africa

      Pandemic H1N1 2009 virus continues to be isolated from all parts of the continent, and there is evidence of continued co-circulation of pandemic (H1N1) 2009 and seasonal H3N2 viruses.

      Oceania

      In the temperate region of the southern hemisphere, little pandemic influenza activity has been reported.

      ILI consultation rates decreased in New Zealand in the week ending 29 November (week 48), with 20.3 per 100,000 population from 27.9 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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      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 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.

      Data Analysis

      Analysis of confirmed cases in done on combined NetEpi and NNDSS data. Analysis of morbidity (hospitalisations and ICU admissions) and mortality data is done 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 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.
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      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.

      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) 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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      References


      1. 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 77 & Virological Surveillance Weekly Update. Available from http://www.who.int/csr/don/en/. Accessed 9 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 9 December 2009.
      5. New Zealand Public Health Surveillance, Influenza Weekly Update 2009/48. Available at: http://www.surv.esr.cri.nz/virology/influenza_weekly_update.php. Accessed 9 December 2009.
      6. CDC FluView Weekly report, Week 47 ending 28 November 2009. Available from: http://www.cdc.gov/flu/weekly/. Accessed 9 December 2009.
      7. Canada FluWatch Weekly report, week ending 28 November 2009 (Week 47). Available from: http://www.phac-aspc.gc.ca/fluwatch/09-10/index-eng.php Accessed 9 December 2009.
      8. Mexico Ministry of Health, Current Epidemic Situation [Influenza], 2 December, 2009. http://portal.salud.gob.mx/descargas/pdf/influenza/situacion_actual_epidemia_021209.pdf Accessed 9 December 2009.
      9. ECDC weekly pandemic update – issue 22, 7 December 2009. Available from: http://ecdc.europa.eu/en/healthtopics/Documents/Forms/AllItems.aspx. Accessed 9 December 2009.
      10. HPA weekly pandemic flu media update for week 49, 3 December 2009. Available from:
      http://www.hpa.org.uk/webw/HPAweb&Page&HPAwebAutoListName/Page/1240732817665?p=1240732817665. Accessed 9 December 2009.
      11. Influenza Surveillance in Ireland - Weekly Update. Influenza week 48. Available from: http://www.hpsc.ie/hpsc/A-Z/EmergencyPlanning/AvianPandemicInfluenza/ Accessed 9 December 2009.