Australian influenza report 2009: 16 to 22 May 2009 (#3-09)

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. It is produced weekly from May to October. A more in-depth end of season report is also published in Communicable Diseases Intelligence.

Page last updated: 05 June 2009

Report No. 3
Week ending 22 May 2009

A print friendly version of this report is available as a PDF (88 KB)

Prepared by the Vaccine Preventable Disease Surveillance Section

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. Please note, this report is based on data available as at 25 May 2009. 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


In this report

  • There has been an increase in influenza notifications over the last few weeks compared to the 5-year rolling mean (Figure 1), likely due to an increase in testing for influenza associated with H1N1 Influenza 09 (Human Swine Influenza).
  • This year to date (1 January 2009 to 22 May 2009) there have been 1,036 cases of influenza notified in Australia. Forty-two percent of these cases have been in New South Wales. The highest rate of notifications as been in the Northern Territory, followed by the Australian Capital Territory.
  • Although the WHO has not released a report on oseltamivir resistance in seasonal H1N1 influenza since 18 March 2009, Europe, the USA and Canada have reported levels of oseltamivir resistance of 98%(to 15 May), 99% (to 16 May) and 100% (to 9 May) respectively. Unlike prevalent seasonal H1N1 strains currently circulating, H1N1 Influenza 09 (Human Swine Influenza) is sensitive to oseltamivir.
  • As of 29 May 2009, there have been 148 confirmed H1N1 Influenza 09 (Human Swine Influenza) cases, 96 in Victoria, 33 in New South Wales, 9 in Queensland, 6 in South Australia, 3 in the Australian Capital Territory, 1 in Western Australia and none in either Tasmania or the Northern Territory.

    Figure 1: Number of notifications of laboratory-confirmed influenza, NNDSS, Australia 1 January 2003 to 22 May 2009, by week of diagnosis



    Figure 1: Number of notifications of laboratory-confirmed influenza, NNDSS, Australia 1 January 2003 to 22 May 2009, by week of diagnosis

    SOURCE: NNDSS
    As influenza only became nationally notifiable in 2001, a 5 year rolling mean cannot be calculated for years prior to 2006.



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    Laboratory confirmed influenza

    There have been 1,036 cases of laboratory confirmed influenza diagnosed year-to-date (YTD) in 2009 (Figure 1). There were 783 laboratory confirmed influenza cases in the same period last year.

    Influenza notifications are above the 5 year rolling mean for this period (Figure 1). The increase in influenza notifications and notification rates in this reporting period (Figures 2 and 3) is likely to be due to increased testing for influenza associated with H1N1 Influenza 09 (Human Swine Influenza).
    Notifications in 2009 have been predominantly from New South Wales, with 432 (41.7%) notifications and Queensland, 248 (23.9%) cases of influenza notified (Table 1; Figure 2).

    Table 1: Number and rate of laboratory-confirmed notifications by jurisdiction, NNDSS, 1 January to 22 May 2009

    State
    Cases Percentage of total notifications Rate per 100,000 Average rate YTD 2004-2008
    ACT
    23
    2.2%
    6.8
    3.3
    NSW
    432
    41.7%
    6.3
    2.7
    NT
    26
    2.5%
    12.1
    6.4
    Qld
    248
    23.9%
    5.9
    4.0
    SA
    106
    10.2%
    6.7
    0.7
    Tas
    11
    1.1%
    2.2
    1.4
    Vic
    78
    7.5%
    1.5
    0.8
    WA
    112
    10.8%
    5.3
    2.4
    Aus
    1,036
    100%
    4.9
    2.3


    Figure 2: Number of laboratory-confirmed influenza notifications, NNDSS, 1 January to 22 May 2009, by jurisdiction and week of diagnosis

    Figure 2: Number of laboratory-confirmed influenza notifications, NNDSS, 1 January to 22 May 2009, by jurisdiction and week of diagnosis

    Source: National Notifiable Diseases Surveillance System



    National age-specific notification rates YTD show the highest rate of notifications occurred in males 80-84 years and children aged less than one year. Notifications in the 10-14 year age group are significantly lower than baseline levels across all ages (Figure 3; Figure 3 insert).

    Figure 3: Notification rates of laboratory-confirmed influenza, NNDSS, Australia, 1 January to 22 May 2009, by age group and sex

    Figure 3: Notification rates of laboratory-confirmed influenza, NNDSS, Australia, 1 January to 22 May 2009, by age group and sex

    Source: National Notifiable Diseases Surveillance System

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    Antigenic characteristics

    Influenza A is the predominant circulating type in Australia. YTD, 800 cases (79%) of influenza notifications to NNDSS have been influenza type A, 159 cases (16%) have been influenza type B and 53 cases (5%) were untyped (Figure 4 and 5). Of the type A notifications that were subtyped, 28 were H3N2 and 20 were H1N1. At the close of this reporting period H1N1 09 (Human Swine Influenza) typing data had not yet been entered into NNDSS. NetEpi is being used as an outbreak management tool to collect H1N1 09 (Human Swine Influenza) cases and these will be transferred to NNDSS as jurisdictions are able (Figure 4).


    Figure 4: Typing characteristics of notifications of laboratory-confirmed influenza, Australia, NNDSS, 1 January to 22 May 2009

    Figure 4: Typing characteristics of notifications of laboratory-confirmed influenza, Australia, NNDSS, 1 January to 22 May 2009

    Source: National Notifiable Diseases Surveillance System


    Figure 5: Typing characteristics of notifications of laboratory-confirmed influenza, NNDSS, Australia, 1 January to 22 May 2009, by week of diagnosis

    Figure 5: Typing characteristics of notifications of laboratory-confirmed influenza, NNDSS, Australia, 1 January to 22 May 2009, by week of diagnosis
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    Syndromic surveillance

    Sentinel general practice

    Data available from the Australian Sentinel Practices Research Network (ASPREN) and the Northern Territory GP surveillance system up until 24 May 2009 show that ILI consultation rates this reporting period, at a presentation rate of 8 cases per 1000 patients seen are lower than the previous reporting period and below levels seen during the same period in 2007 and 2008 (Figure 6). There is no apparent ongoing increase in the number of people visiting their GPs with ILI compared to previous years as a result of the large amount of media around H1N1 Influenza 09 (Human Swine Influenza).

    Figure 6: Rate of influenza-like illness reported from general practitioner influenza-like illness systems, 1 January 2007 to 24 May 2009, by week


    Figure 6: Rate of influenza-like illness reported from general practitioner influenza-like illness systems, 1 January 2007 to 24 May 2009, by week

    Source: Australian Sentinel Practice Research Network and Northern Territory

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    Absenteeism surveillance

    A national organisation provides data on the number of employees that 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.

    Absenteeism rates in 2009 continue to follow similar trends to recent years and may indicate that influenza is not widespread in the community (Figure 7).

    Figure 7: Absenteeism rates, 1 January 2007 to 29 April 2009, by week and NNDSS influenza notifications, rate per 100,000 population, 1 January 2009 to 22 May 2009, by week


    Figure 7: Absenteeism rates, 1 January 2007 to 29 April 2009, by week and NNDSS influenza notifications, rate per 100,000 population, 1 January 2009 to 15 May 2009, by week

    Source: Absenteeism data


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    International seasonal activity summary

    Global, Europe, United States and Canada

    During weeks 17-18, the level of seasonal influenza activity in the northern hemisphere continued to decrease, but local seasonal influenza activity was reported by Canada, the Russian Federation and the United States of America. However, more countries in the southern hemisphere reported sporadic seasonal influenza activity. Mexico reported regional seasonal influenza activity due to low level influenza B activity and increased testing for H1N1 Influenza 09 (Human Swine Influenza). The strains reported from countries experiencing local and sporadic seasonal influenza activity varied between seasonal influenza A (H1 and H3) and influenza B.1

    In Europe, since 2008-2009 seasonal reporting commenced on 29 September 2008, influenza A has been the predominant circulating type, with H3 being the predominant strain of the isolates subtyped. Seasonal influenza activity is at baseline levels for most countries in Europe.2 Oseltamivir resistance has been detected in 98% of seasonal influenza H1N1 isolates tested as at 15 May 2009.3

    In The United States, since 2008-2009 seasonal influenza reporting commenced on 30 September 2008, influenza A has been the predominant circulating type, with H1N1 being the predominant strain of the isolates subtyped. Oseltamivir resistance has been detected in 99% of the seasonal influenza H1N1 isolates tested.4
    In Canada, since 2008-2009 seasonal reporting commenced on 24 August 2008, influenza A has been the predominant circulating type. During the reporting, Canada reported a slight increase in seasonal influenza activity, consultation rates and proportion of positive tests for influenza A. Oseltamivir resistance has been detected in 100% of influenza H1N1 isolates tested as at
    9 May 2009.5

    1. WHO, seasonal influenza activity in the world weeks 17 & 18. Available from: http://www.who.int/csr/disease/influenza/update/en/index.html. Accessed 22 May 2009
    2. EISS Weekly Electronic Bulletin Influenza Season 2008-2009, weeks 18 & 19. Available from: http://www.eiss.org/cgi-files/bulletin_v2.cgi?season=2008. Accessed 22 May 2009.
    3. ECDC Antivirals of Influenza Antiviral Resistant Influenza. Available from: http://ecdc.europa.eu/en/Health_Topics/influenza/antivirals.aspx. Accessed 22 May 2009
    4. CDC FluView 2008-2009 influenza season, weeks 15 & 17. Available from: http://www.cdc.gov/flu/weekly/. Accessed 22 May 2009.
    5. Flu Watch Weekly reports 2008-2009 season, weeks 17 & 18 2009. Available from: http://www.phac-aspc.gc.ca/fluwatch/08-09/index-eng.php. Accessed 22 May 2009.



    Figure 8: Weekly consultation rates for influenza-like illness in New Zealand, 2007, 2008 and 2009

    Figure 8: Weekly consultation rates for influenza-like illness in New Zealand, 2007, 2008 and 2009

    For further information please contact: flu@health.gov.au

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    Data considerations

    NNSSS (National Notifiable Diseases Surveillance System)

    NNDSS comprises of notifications from jurisdictions of laboratory-confirmed influenza cases. Influenza is notifiable in all jurisdictions in Australia. Data included in this report was extracted and analysed on 25 May 2008.

    GP Surveillance

    ASPREN, the Australian Sentinel Practices Research Network, has Sentinel GPs who report 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 to that of previous years.

    ASPREN data are sent to the Surveillance Branch on a weekly basis, and are currently available up until 24 May 2009.

    Northern Territory GP surveillance data are sent to the Surveillance Branch on a weekly basis, and are currently available up to 17 May 2009.

    Absenteeism Surveillance

    Absenteeism data are provided weekly to the Surveillance Branch by a national employer and are currently available up until 6 May 2009.
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