Australian influenza report 2012 - 21 July - 3 August 2012 (#5/2012)

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: 15 August 2012

Report No. 5
Week ending 3 August 2012

PDF printable version of Australian Influenza Surveillance Report No 5 - 2012 (PDF 1993 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 (NNDSS);
    • general practitioner (GP) consultations for influenza-like illness (ILI);
    • emergency department (ED) presentations for ILI;
    • ILI-related call centre calls and community level surveys of ILI; and
    • sentinel laboratory test results.
How severe is the disease, and is severity changing?Indicated by trends in:
    • hospitalisations, intensive care unit (ICU) admissions and deaths; and
    • clinical severity in hospitalised cases and ICU admissions.
Is the virus changing?Indicated by trends in:
    • drug resistance; and
    • antigenic drift or shift of the circulating viruses.

Summary

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  • Nationally across most surveillance systems influenza activity continued to decrease this fortnight.
  • Although some jurisdictions have continued to report widespread activity above baseline levels, influenza activity decreased across most of Australia.
  • Influenza-like illness (ILI) activity has continued to decrease, with current ILI activity levels similar to the peak levels experienced during the 2010 and 2011 seasons.
  • During this fortnight there were 6,095 laboratory confirmed notifications of influenza. Nationally, notifications appear to have plateaued. However, almost 45% of notifications this fortnight were from Queensland, where there continues to be an increasing trend.
  • Nationally, influenza A(H3N2) remains the predominant circulating virus with some co-circulation of influenza B, however this varies by jurisdiction. So far in 2012 there have been very few notifications of pandemic (H1N1) 2009.
  • In 2010 and 2011 with the predominance of the pandemic (H1N1) 2009 virus, the age distribution of notifications showed a downward trend with increasing age. With the predominance of influenza A(H3N2) in 2012, the age distribution of notifications are currently reflective of traditional pre-pandemic seasons with peaks among those aged 0-4 and over 70 years.
  • As at 3 August 2012, there have been 23,553 confirmed cases of influenza reported. Excluding 2009, notifications of influenza in 2012 started their seasonal increase earlier and rose sharply in comparison to previous years. The intensity of the rise in cases for 2012 has also meant a higher peak in notifications, however the total number of notifications for the entire season may not result in a substantial variance compared to previous seasons.
  • Influenza associated hospitalisations have decreased this fortnight. Known medical co-morbidities have been reported in 76% of hospitalised cases and there is a bimodal age distribution trend in hospitalisations, with peaks among those aged 0-9 years and over 70 years.
  • The WHO has reported that the influenza season has continued in the temperate countries of the southern hemisphere. Influenza A(H3N2) viruses have been the most commonly reported, however there is a predominance of pandemic (H1N1) 2009 in some counties of central and tropical South America.
  • The United States have reported an additional 153 human cases associated with a variant swine influenza A(H3N2) virus since July 2012. All of the current cases are associated with direct or indirect contact with swine, the majority at agricultural fairs. Viruses detected in the current cases are similar to the variant viruses identified during July 2011 to April 2012.

1. Geographic Spread of Influenza Activity in Australia

In the fortnight ending 3 August 2012, the geographic spread of influenza activity reported by state and territory Health Departments was ‘widespread’ in Tasmania, Victoria, the ACT, New South Wales, South Australia, central Queensland and the southern part of Western Australia; and ‘regional’ in the remaining areas, except in the Central region of the Northern Territory where activity was reported as ‘localised’ (figure 1). Across most of Australia influenza activity was reported as decreasing or no change in activity. During this period only Queensland reported evidence of an increase in ILI via syndromic surveillance systems. Definitions of these activity levels are provided in the Data Considerations section of this report.

Figure 1. Map of influenza activity by state and territory, 21 July to 3 August 2012

Figure 1. Map of influenza activity by state and territory, 21 July to 3 August 2012


2. Influenza-like illness activity

Community Level Surveillance

FluTracking

FluTracking, a national online system for collecting data on ILI in the community, noted that in the week ending 5 August 2012 fever and cough was reported by 3.6% of vaccinated participants and 4.4% of unvaccinated participants (figure 2) 1. Fever, cough and absence from normal duties was reported by 2.4% of vaccinated participants and 2.9% of unvaccinated participants. Current rates of ILI among FluTracking participants are trending slightly higher compared with previous years, excluding 2009. In the most recent fortnight there has been a decline in the reported rates of ILI (figure 3).

Up to 5 August 2012, 53.9% of participants reported having received the seasonal vaccine so far. Of the 2,635 participants who identified as working face-to-face with patients, 73.1% have received the vaccine.

Figure 2. Proportion of cough and fever among Flutracking participants, week ending 6 May 2012 to 5 August 2012, by vaccination status and week

Figure 2. Proportion of cough and fever among Flutracking participants, week ending 6 May 2012 to 5 August 2012, by vaccination status and week

Source:FluTracking1


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Figure 3. Proportion of fever and cough among FluTracking participants between May and October, 2008 to 2012, by week

Figure 3. Proportion of fever and cough among FluTracking participants by week, between May and October, 2008 to 2012

Source: FluTracking1


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National Health Call Centre Network
In the week ending 5 August 2012, the number of ILI related calls to the National Health Call Centre Network (NHCCN) continued to decrease to 1,287 and representing 9.3% of total calls. This decrease follows a peak of 1,836 ILI related calls (12.7%) in mid-July. The number and proportion of ILI weekly related calls to the NHCCN in 2012 have been higher than the peaks experienced in 2010 and 2011(figure 4).

Figure 4. Number of calls to the NHCCN related to ILI and percentage of total calls, Australia, 1 January 2010 to 5 August 2012, by week

]Figure 4. Number of calls to the NHCCN related to ILI and percentage of total calls, Australia, 1 January 2010 to 5 August 2012, by week


Note: NHCCN data do not include Queensland and Victoria
Source: NHCCN data


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Sentinel General Practice Surveillance

In the week ending 5 August 2012, sentinel general practitioner ILI consultation rates remained relatively stable at 18.6 cases per 1,000 consultations (figure 5). Compared with previous years (excluding 2009), there has been an earlier increase in ILI consultation rates and rates are higher than the seasonal peaks reported in 2010 and 2011.

Figure 5. Weekly rate of ILI reported from GP ILI surveillance systems from 1 January 2008 to 5 August 2012, by week*

Figure 5. Weekly rate of ILI reported from GP ILI surveillance systems from 1 January 2008 to 5 August 2012, by week

* 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 with 2010-2012.
Source: ASPREN and VIDRL2 GP surveillance system.


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In the fortnight ending 5 August 2012, specimens were collected from just over half of ASPREN ILI patients. Of these patients, 49% were positive for influenza, down from 58% in the previous fortnight. Thirty-eight per cent were positive for influenza type A, with the majority likely to be attributed to A (H3N2); and the remaining 11% were influenza type B (figure 6 and table 1). Around 16% per cent of specimens collected were positive for other respiratory viruses this fortnight, with the majority of these being either rhinovirus, RSV or human metapneumovirus.

Table 1. ASPREN laboratory respiratory viral test results of ILI consultations, 1 January 2012 to 5 August 2012.

Fortnight
(23 July – 5 August 2012)
YTD
(1 January – 5 August 2012)
Total specimens tested
456
2205
Total Influenza Positive (%)
48.9
40.0
Influenza A (%)
37.9
29.1
Pandemic (H1N1) 2009 (%)
0.7
0.6
Influenza A (unsubtyped) (%) #
37.3
28.5
Influenza B (%)
11.0
10.8
Other Resp. Viruses (%)*
16.2
19.9

# The majority of type A(unsubtyped) notifications are likely to be attributed to A(H3N2)
* Other respiratory viruses include RSV, parainfluenza, adenovirus and rhinovirus.


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Figure 6. Proportion of respiratory viral tests positive for influenza in ILI patients and GP ILI consultation rate, 1 January 2012 to 5 August 2012, by week

Figure 6. Proportion of respiratory viral tests positive for influenza in ILI patients and GP ILI consultation rate, 1 January 2012 to 5 August 2012, by week

Source: ASPREN and WA SPN


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Sentinel Emergency Department Surveillance

Western Australia Emergency Departments
In the fortnight ending 5 August 2012, respiratory viral presentations to Perth emergency departments continued to decrease. The current levels are similar to the peak levels experienced in previous years (excluding 2009) (figure 7). Over this period there were 1,413 presentations, including 106 admissions. The proportion of presentations requiring admission to hospital over this period was 7.5%.

Figure 7. Number of respiratory viral presentations to Western Australia emergency departments, 1 January 2008 to 5 August 2012, by week

Figure 7. Number of respiratory viral presentations to Western Australia emergency departments, 1 January 2008 to 5 August 2012, by week

Source: WA ‘Virus Watch’ Report3.


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New South Wales Emergency Departments
In the week ending 3 August 2012 the number of patients presenting to NSW emergency departments continued to decrease (figure 8). Emergency department presentations are considered to be within the usual range for this time of year. Total admissions from emergency departments to critical care units for ILI and pneumonia also decreased this week.4

Figure 8. Rate of influenza-like illness presentations to New South Wales emergency departments, between May and October, 2008 to 2012, by week*

Figure 8. Rate of influenza-like illness presentations to New South Wales emergency departments, between May and October, 2008 to 2012, by week

Source: NSW Influenza Weekly Epidemiology Report4


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Northern Territory Emergency Departments
In the fortnight ending 4 August 2012, the number of patients presenting with ILI to emergency departments across the Northern Territory decreased to 440 from 483 in the previous fortnight. The number of presentations to emergency departments in the Northern Territory since May 2012 have been slightly higher compared to previous years (excluding 2009), however they remain below the peak reported in 2011 (figure 9).

Figure 9. Number of ILI presentations to Northern Territory emergency departments, 1 January 2008 to 4 August 2012, by week

Figure 9. Number of ILI presentations to Northern Territory emergency departments, 1 January 2008 to 4 August 2012, by week

Source: Centre for Disease Control, Department of Health, Northern Territory Government


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3. Laboratory confirmed influenza activity

Notifications of Influenza to Health Departments

During the reporting period there were 6,095 laboratory confirmed influenza notifications reported to the NNDSS, with a slight decrease compared to the previous fortnight (6,475). Nationally, notifications appear to have plateaued (figure 10). Almost 45% of notifications this fortnight were from Queensland (2,664) where there continues to be an increasing trend. Notifications reported from all other jurisdictions this fortnight were: Western Australia (903), South Australia (779), Victoria (727), New South Wales (548), Tasmania (347), the ACT (94) and the NT (33). A weekly breakdown of trends by state and territory highlights that whilst there continues to be increases in Queensland, notifications have plateaued in Western Australia, Victoria and Tasmania, and have continued to decrease across all other jurisdictions (figure 11).

Figure 10. Laboratory confirmed cases of influenza in Australia, 1 January to 3 August 2012, by state or territory and week.

Figure 10. Laboratory confirmed cases of influenza in Australia, 1 January to 3 August 2012, by state or territory and week

Source: NNDSS



Figure 11. Notifications of laboratory confirmed cases of influenza, 1 January to 3 August 2012, by state or territory and week

Figure 11. Notifications of laboratory confirmed cases of influenza, 1 January to 3 August 2012, by state or territory and week

Source: NNDSS


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In 2010 and 2011 with the predominance of the pandemic (H1N1) 2009 virus, the age distribution of influenza notifications showed a downward trend with increasing age. However, in 2012 with the predominance of influenza A(H3N2), the age distribution of influenza notifications has shown a bimodal trend with peaks in those aged 0-4 years and in those aged 70 years and over, with a small peak among those aged 30-44 years. This age distribution is more reflective of traditional pre-pandemic seasons (figure 12).

Figure 12. Rates of laboratory confirmed influenza, 1 January 2008 to 3 August 2012, by age group

Figure 12. Rates of laboratory confirmed influenza, 1 January 2008 to 3 August 2012, by age group

Source: NNDSS


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Up to 3 August, there have been 23,553 laboratory confirmed notifications of influenza diagnosed during 2012 (figure 13). Of these notifications, there have been 7,311 in Queensland, 4,967 in New South Wales, 3,771 in South Australia, 3,090 in Western Australia, 2,879 in Victoria, 799 in Tasmania, 463 in the ACT and 273 in the Northern Territory.

Figure 13. Notifications of laboratory confirmed influenza, Australia, 1 January 2008 to 3 August 2012, by week

Figure 13. Notifications of laboratory confirmed influenza, Australia, 1 January 2008 to 3 August 2012, by week

Source: NNDSS


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Of the 6,095 influenza notifications reported to the NNDSS this reporting period, 5,225 were influenza A (4,139 were influenza A (unsubtyped), 1,062 were A(H3N2) and 24 were pandemic (H1N1) 2009), 866 were influenza B and 4 notifications were reported as A&B coinfections or untyped (figure 13). The majority of type A (unsubtyped) notifications are likely to be attributed to A(H3N2).

Up to 3 August 2012, 19,877 cases (84%) were reported as influenza A (63% influenza A (unsubtyped), 20% A(H3N2) and 1% pandemic (H1N1) 2009) and 3,610 (15%) were influenza B. A further 37 (<1%) were influenza type A&B, 1 (<1%) was influenza C, and 25 (<1%) were untyped (figure 14).

Nationally, influenza A(H3N2) continues to be the predominant circulating strain with some co-circulation of influenza B. Influenza A(H3N2) is predominant across most states and territories, however influenza B represents around a third of notifications in Western Australia and 20% in the Northern Territory, with this proportion steadily decreasing. So far in 2012 there have been very few notifications of pandemic (H1N1) 2009 reported. In recent years, the proportion influenza A(H3N2) viruses circulating in the community has been low. This may have led to some reductions in immunity across the population and thus be a contributing factor to both the predominance of this virus among the population and the apparent intensity of the season.

Figure 14. Notifications of laboratory confirmed influenza, Australia, 1 January to 3 August 2012, by sub-type and week

Figure 14. Notifications of laboratory confirmed influenza, Australia, 1 January to 3 August 2012, by sub-type and week

Source: NNDSS


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Sentinel Laboratory Surveillance

Results from sentinel laboratory surveillance systems for this reporting period show that 37.8% of the respiratory viral tests conducted over this period were positive for influenza, a slight decrease from 38.6% in the previous fortnight (table 2). Influenza A(H3N2) was the predominant influenza virus reported. A breakdown of subtypes within this positive proportion by fortnight is highlighted in figure 15.

Table 2. Sentinel laboratory respiratory virus testing results, 7 July to 3 August 2012

NSW NIC
WA NIC
VIC NIC
TAS
(PCR Testing Data)
Total specimens tested
439
1639
348
707
Total influenza positive
59
738
86
302
Positive influenza A
52
517
82
291
Pandemic (H1N1) 2009
0
6
4
1
A (H3N2)
52
510
75
81
A (unsubtyped)
0
1
3
209
Positive influenza B
7
217
4
11
Positive influenza A&B
0
4
0
0
Proportion Influenza Positive (%)
13.4%
45.0%
24.7%
42.7%
Most common respiratory virus detected
Influenza A
Influenza A
Influenza A
Influenza A

Source: National Influenza Centres (WA, Vic, NSW) and Tasmanian laboratories (PCR testing)


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Figure 15. Proportion of sentinel laboratory tests positive for influenza, 26 May to 3 August 2012, by subtype and fortnight

Figure 15. Proportion of sentinel laboratory tests positive for influenza, 26 May to 3 August 2012, by subtype and fortnight

Source: National Influenza Centres (WA, Vic, NSW) and Tasmanian laboratories (PCR testing)


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Hospitalisations

Influenza Complications Alert Network (FluCAN)
The Influenza Complications Alert Network (FluCAN) sentinel hospital surveillance system has reported that the number of confirmed influenza hospital admissions appears to have plateaued in the most recent fortnight, following a peak in admissions in mid-July. Since 7 April 2012, 8% of influenza patients have been admitted directly to ICU. Overall, 17% of cases have been due to influenza B (figure 16), however almost half of these presentations are from the Northern Territory, with influenza A more common in other states. Around 45% of the cases are aged 65 years and over (median age 61 years) and 76% of all cases have known medical co-morbidities.

Figure 16. Number of influenza hospitalisations at sentinel hospitals, 7 April to 3 August 2012, by week and influenza subtype

Figure 16. Number of influenza hospitalisations at sentinel hospitals, 7 April to 3 August 2012, by week and influenza subtype

Source: FluCAN Sentinel Hospitals


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Queensland Public Hospital Admissions (EpiLog)
Admissions to public hospitals in Queensland of confirmed influenza are detected through the EpiLog system. Up to 5 August 2012, there have been 889 admissions of confirmed influenza, including 85 to intensive care units. In the most recent fortnight, hospital admissions appear to have peaked, with a slight decrease in the most recent week (figure 17). The age distribution of confirmed influenza admissions in 2012 shows a bimodal distribution peaking in the 0-9 and also the 70 years and over age groups.

Figure 17. Number of influenza admissions to Queensland public hospitals, with onset from 1 January to 5 August 2012, by week and type of admission

Figure 17. Number of influenza admissions to Queensland public hospitals, with onset from 1 January to 5 August 2012, by week and type of admission

Source: Queensland Health EpiLog data


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Paediatric Severe Complications of Influenza
The Australian Paediatric Surveillance Unit conducts seasonal surveillance of children aged 15 years and under who are hospitalised with severe complications of influenza. Between 1 July and 6 August 2012, there have been 13 hospitalisations associated with severe complications of influenza, including 5 ICU admissions. Around half of these hospitalisations were associated with influenza A(unsubtyped), with the other half reported as influenza type B. Half of the cases had an underlying chronic condition.

Deaths associated with influenza and pneumonia

Nationally Notified Influenza Associated Deaths
So far in 2012, 23 influenza associated deaths have been notified to the NNDSS, with a median age of 74 years. Almost all cases were reported as having influenza A(unsubtyped) or A(H3N2), with the A(unsubtyped) infections also likely to be attributable to A(H3N2). The number of influenza associated deaths reported to the NNDSS are reliant on the followup of cases to determine the outcome of their infection and most likely do not represent the true mortality impact associated with this disease.
Death registration data for the week ending 20 July 2012 show that there were 1.5 pneumonia or influenza associated deaths per 100,000 population in NSW, which is below the epidemic threshold of 1.7 per 100,000 NSW population for this period (Figure 18).4

Figure 18. Rate of deaths classified as influenza and pneumonia from the NSW Registered Death Certificates, 1 January 2007 to 20 July 2012

Figure 18. Rate of deaths classified as influenza and pneumonia from the NSW Registered Death Certificates, 1 January 2007 to 20 July 2012

Source: NSW ‘Influenza Weekly Epidemiology Report’4


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4. Virological Surveillance

Typing and antigenic characterisation

WHO Collaborating Centre for Reference & Research on Influenza (WHO CC), Melbourne
From 1 January to 6 August 2012, there were 695 Australian influenza viruses subtyped by the WHO CC with almost two-thirds being influenza A(H3N2) and a third influenza B. So far this year, very few viruses have been pandemic (H1N1) 2009 (table 3).

Table 3. Australian Influenza viruses typed by HI or PCR from the WHO Collaborating Centre, 1 January 2012 to 6 August 2012

Type/Subtype
ACT
NSW
NT
QLD
SA
TAS
VIC
WA
TOTAL
Pandemic (H1N1) 2009
0
0
1
2
1
0
11
5
20
A(H3N2)
8
48
0
83
86
23
181
12
441
B
2
9
45
66
28
4
44
36
234
Total
10
57
46
151
115
27
236
53
695

Source: WHO CC
Note: There may be up to a month delay on reporting of samples.
Viruses tested by the WHO CC are not necessarily a random sample of all those in the community.


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The WHOCC has analysed some of the currently circulating influenza viruses. Whilst almost all of the influenza A(H3N2) viruses are of a more recent strain that differs from the A(H3N2) strain in the 2012 Southern Hemisphere seasonal influenza vaccine, it is expected that the vaccine will still offer significant protection. Additionally there is some co-circulation of the two influenza B lineages. The majority of influenza B viruses are of the B/Victoria lineage and are similar to the strain in the current vaccine. Some cross-protection against influenza B viruses of the other (B/Yamagata) lineage is expected in adults, though less so for children. The next northern hemisphere vaccine (2012-13) will include a B/Yamagata lineage virus instead of the current B/Victoria lineage virus.

Antiviral Resistance

The WHO CC has reported that from 1 January to 6 August 2012, one influenza virus (out of 603 tested) has shown resistance to the neuraminidase inhibitor oseltamivir. This virus was a pandemic (H1N1) 2009 virus with H275Y mutation in the neuraminidase gene, which is known to confer resistance to oseltamivir.

2012/13 Northern Hemisphere Vaccine

In February 2012 the WHO recommended that vaccines for the 2012-2013 influenza season (northern hemisphere winter) contain the following:
    • an A/California/7/2009 (H1N1)pdm09-like virus;
    • an A/Victoria/361/2011 (H3N2)-like virus;
    • a B/Wisconsin/1/2010-like virus5
In comparison to the current 2012 southern hemisphere vaccine, the recommended A(H3N2) and B viruses have been changed. The WHO notes in their recommendations that5:
    • the majority of recent A(H3N2) viruses were antigenically and genetically distinguishable from the current southern hemisphere vaccine virus (A/Perth/16/2009) and were more closely related to A/Victoria/361/2011-like reference viruses.
    • the proportion of B/Yamagata/16/88 lineage viruses increased in many parts of the world but B/Victoria/2/87 lineage viruses predominated in some countries. The majority of recent B/Victoria/2/87 lineage viruses were antigenically and genetically closely related to the current southern hemisphere vaccine virus (B/Brisbane/60/2008). Most recently isolated B/Yamagata/16/88 lineage viruses were antigenically distinguishable from the previous vaccine virus B/Florida/4/2006 and were closely related to B/Wisconsin/1/2010-like viruses.
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5. International Influenza Surveillance

The WHO6has reported that as at 3 August 2012 the influenza season has continued in most temperate countries of the southern hemisphere, although influenza levels remain very low in Argentina. The season appears to have peaked in Chile and South Africa, where many indicators have recently begun to decline. In the tropical zone, there is notable influenza activity in Brazil, Cuba, Ecuador, El Salvador and Panama in the Americas (mostly pandemic (H1N1) 2009 and type B); Ghana and Madagascar in sub-Saharan Africa( mostly influenza A(H3N2)); southern China, Singapore and Viet Nam in Asia (a mixture of all three types/subtypes). A detailed review of the 2011/12 northern hemisphere season is available at the WHO website.

In New Zealand7, for the week ending 5 August 2012, the national weekly rate of ILI consultations continue to increase and are currently 154.1 per 100,000 patient population, which is well above baseline activity levels (50 per 100,000 patient population). Eight of the twenty district health boards were above the national average weekly consultation rate. Virological surveillance through both sentinel and non-sentinel laboratories shows that so far this year 66% have been influenza A(H3N2) viruses, 8% influenza B viruses and 13% were pandemic (H1N1) 2009 virus detections, with the remainder being influenza A (unsubtyped). It is noted that currently influenza A(H3N2) viruses remain the predominant virus in many regions.

In the southern hemisphere temperate region, influenza A(H3N2) viruses were the most commonly reported type/subtype in Chile, South Africa, Australia and New Zealand. Although there have been very few reports of pandemic (H1N1) 2009 in the southern hemisphere temperate region, pandemic (H1N1) 2009 is currently the most commonly detected virus in Paraguay as well as neighbouring areas of southern Brazil and parts of Bolivia. 6 National Influenza Centres and laboratories in 60 countries, areas or territories, have reported that for the period 8 July to 21 July 2012, a total of 2,591 specimens were reported as positive for influenza viruses, with 77% being influenza A and 23% influenza B. Of the sub-typed influenza A viruses, 89% were influenza A(H3N2) and 11% were pandemic (H1N1) 2009. Of the characterised influenza B viruses, 64% belong to the B/Yamagata lineage and 36% to the B/Victoria lineage.8.

Influenza A (H3N2) Variant Viruses – United States of America

The United States CDC9,10,11 have reported additional infections associated with a variant swine influenza A(H3N2) virus following initial detection of the virus in humans in July 2011. The variant virus contains the M gene from the human pandemic (H1N1) 2009 virus, which may confer increased transmissibility to and among humans. Between 12 July and 9 August 2012, 153 cases have been detected, with the majority of cases in persons aged less than 18 years (median age 7 years)9. All of the current cases have reported direct or indirect contact with swine, the majority at agricultural fairs. Most human illness with the variant virus have been generally consistent with signs and symptoms of seasonal influenza; although there have been 3 hospitalisations, these have occurred in cases with high-risk conditions10,11. Viruses identified since July 2012 are similar to the 13 variant A(H3N2) viruses identified during July 2011 to April 2012. During 2011, there was evidence of limited human-to-human transmission in some cases.

6. 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 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.
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Geographic Spread of Influenza Activity


Influenza Activity Levels
Activity levelLaboratory notificationsInfluenza outbreaks
SporadicSmall no of lab confirmed influenza detections (not above expected background level)+ ANDNo outbreaks
LocalisedRecent increase in lab confirmed influenza detections above background level ++ in less than 50% of the influenza surveillance regions** within the state or area ORSingle outbreak only
RegionalSignificant*** recent increase in lab confirmed influenza detections above baseline in less than 50% of the influenza surveillance regions within the state or area OR> 1 outbreaks occurring in less than 50% of the influenza surveillance regions within the state or area+++
Widespread Significant recent increase in lab confirmed influenza detections above baseline in equal to or greater than 50% of the influenza surveillance regions within the state or areaOR> 1 outbreaks occurring in equal to or greater than 50% of the influenza surveillance regions within the state or area

+ Small no of lab detections = not above expected background level as defined by state epidemiologists.
++ Increase in lab confirmed influenza detections = above expected threshold as defined by state epidemiologists.
** Influenza surveillance region within the state/area as defined by state epidemiologists.
*** Significant increase is a second threshold to be determined by the state epidemiologists to indicate level is significantly above the expected baseline.
+++ Areas to be subdivision of NT (2 regions), WA (3 regions) and QLD (3 regions) that reflect significant climatic differences within those states resulting in differences in the timing of seasonal influenza activity on a regular basis.
Recent = within the current reporting period.


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Syndromic Surveillance Activity
Syndromic surveillance systems*
No evidence of increase in ILI via syndromic surveillance systems
Evidence of increase in ILI via syndromic surveillance systems

* Syndromic surveillance systems = GP sentinel surveillance, ED ILI surveillance, Flu tracking (this may be due to a variety of respiratory viruses so the report could add a note to indicate if other evidence suggests that the increase is suspected to be influenza activity or due to another respiratory pathogen). Syndromic surveillance is reported on a state wide basis only



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 is available at FluTracking.

Sentinel General Practice Surveillance

The sentinel general practice ILI surveillance data between 2008 and 2012 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 2012 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.
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Further information is available at ASPREN and information regarding the VIDRL coordinated sentinel GP ILI surveillance program.

Sentinel Emergency Department Data

Western Australia – Emergency Department ILI surveillance data are extracted from the ‘Virus Watch’ Report. This report is produced 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.
Northern Territory – this sentinel program collects data from the following hospitals: Royal Darwin, Gove District, Katherine District, Tennant Creek and Alice Springs. The definition of ILI is presentation to ED in the NT with one of the following presentations: febrile illness, cough, respiratory infection, or viral illness.

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 the Department of Health and Ageing's website. 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 data

Laboratory 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.

Influenza Complications Alert Network (FluCAN)

The Influenza Complications Alert Network (FluCAN) sentinel hospital system monitors influenza hospitalisations at the following sites:
  • Australian Capital Territory – the Canberra Hospital and Calvary Hospital;
  • New South Wales – John Hunter Hospital and Westmead Hospital;
  • Northern Territory – Alice Springs Hospital;
  • Queensland – the Mater Hospital, Princess Alexandria Hospital and Cairns Base Hospital;
  • South Australia – Royal Adelaide Hospital;
  • Tasmania – Royal Hobart Hospital;
  • Victoria – Geelong Hospital, Royal Melbourne Hospital, Monash Medical Centre and Alfred Hospital;
  • Western Australia – Royal Perth Hospital.
Influenza counts are based on active surveillance at each site for admissions with PCR-confirmed influenza in adults. Some adjustments may be made in previous periods as test results become available. ICU status is as determined at the time of admission and does not include patients subsequently transferred to ICU.

Queensland Public Hospital Admissions (EpiLog)

EpiLog is a web based application developed by Queensland Health. This surveillance system generates admission records for confirmed influenza cases through interfaces with the inpatient information and public laboratory databases. Records are also able to be generated manually. Admissions data reported are based on date of reported onset.

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. Notifications of influenza associated deaths are likely to underestimate the true number of influenza associated deaths occurring in the community.
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NSW influenza and pneumonia deaths data are collected from the NSW Registry of Births, Deaths and Marriages. Figure 16 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

Data on Australian influenza viruses are provided weekly to the Department from the WHO Collaborating Centre for Reference & Research on Influenza based in Melbourne, Australia.

7. References


1 FluTracking, Weekly Interim Report, Week #14 ending 5 August 2012. [Accessed 10 August 2012].
2 Victorian Infectious Disease Reference Laboratory, The 2012 Victorian Influenza Vaccine Effectiveness Audit Report, Report 14, 5 August 2012. [Accessed 10 August 2012]
3 Western Australia Health, Virus WAtch, Week Ending 5 August 2012. [Accessed 10 August 2012]
4 NSW Health, Influenza Weekly Epidemiology Report, 28 July to 3 August 2012. [Accessed 10 August 2012]
5 WHO, Recommended composition of influenza virus vaccines for use in the 2012-13 northern hemisphere influenza season. [Accessed 15 June 2012]
6 WHO, Influenza Update No. 165, 3 August 2012. [Accessed 10 August 2012]
7 New Zealand Influenza Weekly Update, 30 July to 5 August 2012. [Accessed 10 August 2012]
8 WHO, Influenza virus activity in the world, 3 August 2012. [Accessed 10 August 2012]
9 Centers for Disease Control and Prevention, Evaluation of Rapid Influenza Diagnostic Tests for Influenza A (H3N2)v Virus and Updated Case Count — United States, 2012, Morbidity and Mortality Weekly Report, 2012, 61 (early release):10 August 2012,1-3. [Accessed 13 August 2012].
10 Centers for Disease Control and Prevention, CDC Reports Cases 18-29 of H3N2v Virus Infection; Continues to Recommend Interim Precautions When Interacting with Pigs, 3 August 2012. [Accessed 7 August 2012]
11 Centers for Disease Control and Prevention, Increase in Influenza A H3N2v Virus Infections in Three U.S. States, 3 August 2012. [Accessed 7 August 2012]

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