Australian influenza report 2012—4 to 17 August 2012 (#6/2012)

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: 04 September 2012

Report No. 6
Week ending 17 August 2012

A print friendly version of this report is available (PDF 1057 KB)

The Department of Health and Ageing (the department) 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 continued to decrease across most of Australia.
  • Influenza-like illness (ILI) activity has continued to decrease, with current ILI activity levels similar to the levels during the same period in the 2010 and 2011 seasons.
  • During this fortnight there were 6,614 laboratory confirmed notifications of influenza. Nationally, notifications continue to plateau. However, almost 56% of notifications this fortnight were from Queensland, where there continues to be an increasing, although slowing, 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 17 August 2012, there have been 30,733 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 continued to decrease following a peak in mid-July. Known medical co-morbidities have been reported in 75% of hospitalised cases.
  • The WHO has reported that influenza activity has decreased in the majority of the temperate countries of the southern hemisphere. Influenza A(H3N2) viruses have been the most commonly reported across the southern hemisphere region, however in some counties of central and tropical South America there is a predominance of pandemic (H1N1) 2009 or influenza B.
  • The United States have reported an additional 71 human cases associated with a variant swine influenza A(H3N2) virus, increasing the total number of cases since July 2012, to 224. All cases in 2012 have been associated with direct or indirect contact with swine, though during 2011 there was some limited human to human transmission reported. 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 17 August 2012, the geographic spread of influenza activity reported by state and territory Health Departments was 'widespread' in Victoria, New South Wales, South Australia and the southern and Kimberley region of Western Australia; and 'regional' in the remaining areas, except in the Central region of the Northern Territory and the northern region of Queensland, where activity was reported as 'localised' (figure 1). Across most of Australia influenza activity was reported as decreasing or no change in activity, with only Victoria and the Kimberley region of Western Australia reporting an increase in activity. During this period New South Wales was the only jurisdiction that 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, 4 to 17 August 2012

Figure 1. Map of influenza activity by state and territory, 4 to 17 August 2012
Legend for Figure 1. (above)

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 19 August 2012 fever and cough was reported by 3.5% 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 19 August 2012, 54.3% of participants reported having received the seasonal vaccine so far. Of the 2,599 participants who identified as working face-to-face with patients, 74.3% have received the vaccine.

Figure 2. Proportion of cough and fever among Flutracking participants, week ending 6 May 2012 to 19 August 2012, by vaccination status and week
Figure 2. Proportion of cough and fever among Flutracking participants, week ending 6 May 2012 to 19 August 2012, by vaccination status and week

Source:FluTracking1


Top of pageFigure 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, between May and October, 2008 to 2012,  by week

Source: FluTracking1

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National Health Call Centre Network
In the week ending 19 August 2012, the number of ILI related calls to the National Health Call Centre Network (NHCCN) continued to decrease to 992 and representing 8.4% 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 19 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 19 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 19 August 2012, sentinel general practitioner ILI consultation rates have decreased and are now at 14.0 cases per 1,000 consultations (figure 5). Compared with previous years (excluding 2009), there has been an earlier increase and higher peak in ILI consultation rates compared with the seasonal peaks reported in 2010 and 2011.

Figure 5. Weekly rate of ILI reported from GP ILI surveillance systems, 1 January 2008 to 19 August 2012, by week*

Figure 5. Weekly rate of ILI reported from GP ILI surveillance systems, 1 January 2008 to 19 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 17 August 2012, specimens were collected from just over half of ASPREN ILI patients. Of these patients, 53% were positive for influenza, slightly up from 48% 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 15% were influenza type B (figure 6 and table 1). Around 14% per cent of specimens collected were positive for other respiratory viruses this fortnight, with the majority of these being rhinovirus, RSV or human metapneumovirus.

Table 1. ASPREN laboratory respiratory viral test results of ILI consultations, 1 January 2012 to 17 August 2012.
 Fortnight
(6 August – 17 August 2012)
YTD
(1 January – 17 August 2012)
Total specimens tested
324
2588
Total Influenza Positive (%)
53.4
44.6
 Influenza A (%)
38.0
30.3
  Pandemic (H1N1) 2009 (%)
0.9
0.6
  Influenza A (unsubtyped) (%) #
37.0
29.6
 Influenza B (%)
15.4
11.3
Other Resp. Viruses (%)*
13.6
19.2

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

Top of pageFigure 6. Proportion of respiratory viral tests positive for influenza in ILI patients and GP ILI consultation rate, 1 January 2012 to 17 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 17 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 19 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 1,330 presentations, including 71 admissions. The proportion of presentations requiring admission to hospital over this period was 5.3%.

Figure 7. Number of respiratory viral presentations to Western Australia emergency departments, 1 January 2008 to 19 August 2012, by week

Figure 7. Number of respiratory viral presentations to Western Australia emergency departments, 1 January 2008 to 19 August 2012, by week

Source: WA 'Virus Watch' Report3.

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New South Wales Emergency Departments
In the week ending 17 August 2012 the number of patients presenting to NSW emergency departments increased slightly but were within the usual range for this time of year (figure 8). Total admissions from emergency departments to critical care units for ILI and pneumonia also increased slightly this week but remain within the usual range.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 18 August 2012, the number of patients presenting with ILI to emergency departments across the Northern Territory have continued to remain relatively stable with a slight increase to 455 from 440 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 18 August 2012, by week

Figure 9. Number of ILI presentations to Norther Territory emergency departments, 1 January 2008 to 18 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 6,614 laboratory confirmed influenza notifications reported to the NNDSS, with a slight decrease compared to the previous fortnight (6,547). Nationally, notifications have continued to plateau (figure 10). Almost 56% of notifications this fortnight were from Queensland (3,690) where there continues to be an increasing, although slowing, trend. Notifications reported from all other jurisdictions this fortnight were: Western Australia (772), Victoria (736), South Australia (636), New South Wales (543), Tasmania (164), the ACT (44) and the NT (29). 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 the NT and have continued to decrease across all other jurisdictions (figure 11).

Figure 10. Notifications of laboratory confirmed influenza, Australia, 1 January to 17 August 2012, by state or territory and week.

Figure 10. Notifications of laboratory confirmed influenza, Australia, 1 January to 17 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

Top of pageIn 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 17 August 2012, by age group

Figure 12. Rates of laboratory confirmed influenza, 1 January 2008 to 17 August 2012, by age group

Source: NNDSS

Top of pageUp to 17 August, there have been 30,733 laboratory confirmed notifications of influenza diagnosed during 2012 (figure 13). Of these notifications, there have been 11,040 in Queensland, 5,719 in New South Wales, 4,457 in South Australia, 3,938 in Western Australia, 3,773 in Victoria, 963 in Tasmania, 538 in the ACT and 305 in the Northern Territory.

Figure 13. Notifications of laboratory confirmed influenza, Australia, 1 January 2008 to 17 August 2012, by week

Figure 13. Notifications of laboratory confirmed influenza, Australia, 1 January 2008 to 17 August 2012, by week

Source: NNDSS

Top of pageOf the 6,614 influenza notifications reported to the NNDSS this reporting period, 5,400 were influenza A (4,568 were influenza A (unsubtyped), 816 were A(H3N2) and 16 were pandemic (H1N1) 2009), 1,202 were influenza B and 12 notifications were reported as A&B coinfections, influenza C or untyped (figure 13). The majority of type A (unsubtyped) notifications are likely to be attributed to A(H3N2).

Up to 17 August 2012, 25,715 cases (84%) were reported as influenza A (64% influenza A (unsubtyped), 19% A(H3N2) and 1% pandemic (H1N1) 2009) and 4,909 (16%) were influenza B. A further 38 (<1%) were influenza type A&B, 3 (<1%) were influenza C, and 71 (<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, with an increased proportion noted in the ACT (36%), New South Wales (20%) and Queensland (18%). 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 17 August 2012, by sub-type and week

Figure 14. Notifications of laboratory confirmed influenza, Australia, 1 January to 17 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 33.6% of the respiratory viral tests conducted over this period were positive for influenza, a decrease from 37.8% 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 17 August 2012

NSW NIC
WA NIC
VIC NIC
TAS
(PCR Testing Data)
Total specimens tested
408
1,491
324
543
Total influenza positive
50
663
75
141
  Positive influenza A
42
481
67
126
    Pandemic (H1N1) 2009
0
3
5
0
    A (H3N2)
40
478
62
0
    A (unsubtyped)
2
0
1
126
  Positive influenza B
8
182
8
15
  Positive influenza A&B
0
3
0
0
Proportion Influenza Positive (%)
12.3%
44.5%
23.1%
26.0%
Most common respiratory virus detected
Influenza / Rhinovirus
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 17 August 2012, by subtype and fortnight

Figure 15. Proportion of sentinel laboratory tests positive for influenza, 26 May to 17 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 be decreasing since the peak in mid-July. Since 7 April 2012, 9% of influenza patients have been admitted directly to ICU. Overall, 16% of cases have been due to influenza B (figure 16), however 40% 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 60 years) and 75% of all cases have known medical co-morbidities.

Figure 16. Number of influenza hospitalisations at sentinel hospitals, 7 April to 17 August 2012, by week and influenza subtype

Figure 16. Number of influenza hospitalisations at sentinel hospitals, 7 April to 17 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 19 August 2012, there have been 1,234 admissions of confirmed influenza this year, including 112 to intensive care units. In the most recent fortnight, hospital admissions have continued the trend of the previous fortnight, reaching a plateau of about 164 admissions per 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 19 August 2012, by week and type of admission

Figure 17. Number of influenza admissions to Queensland public hospitals, with onset from 1 January to 19 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 17 August 2012, there have been 17 hospitalisations associated with severe complications of influenza, including 5 ICU admissions. More than 60% of hospitalisations, where typing was available, were associated with influenza A(unsubtyped), with the remaining hospitalisations associated with influenza type B. Almost half of the cases had an underlying chronic condition reported.

Deaths Associated with Influenza and Pneumonia

Nationally Notified Influenza Associated Deaths
So far in 2012, 33 influenza associated deaths have been notified to the NNDSS, with a median age of 75 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 follow up of cases to determine the outcome of their infection and most likely do not represent the true mortality impact associated with this disease.
New South Wales Influenza and Pneumonia Death Registrations
Death registration data for the week ending 27 July 2012 show that there were 2.0 pneumonia or influenza associated deaths per 100,000 population in NSW, which is above 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 27 July 2012

Figure 18. Rate of deaths classified as influenza and pneumonia from the NSW Registered Death Certificates, 1 January 2007 to 27 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 21 August 2012, there were 879 Australian influenza viruses subtyped by the WHO CC with two-thirds being influenza A(H3N2) and nearly 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 21 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)
18
52
0
84
90
36
277
30
587
B
2
13
48
66
28
6
50
59
272
Total
20
65
49
152
119
42
338
94
879

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

Top of pageThe 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.

Recent analysis of the B/Brisbane/60/2008-like viruses suggests that around 45% are 'low reactor' compared with the reference virus. As these low reactor viruses do not form a distinct genetic group among the B/Victoria lineage viruses, they are not considered to represent an emerging antigenic drift variant.

Antiviral Resistance

The WHO CC has reported that from 1 January to 21 August 2012, one influenza virus (out of 762 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, and
    • 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 WHO6 has reported that as at 17 August 2012, in tropical zone countries active influenza virus transmission is most notable in Brazil, Cuba, El Salvador, Honduras and Panama (pandemic (H1N1) 2009 and type B). A few areas of tropical Asia have experienced recent significant influenza virus circulation, most notably China, Singapore and Viet Nam (mostly A(H3N2)).

In the southern hemisphere temperate region, most countries reported a decrease in influenza activity except in New Zealand. In New Zealand7, for the week ending 19 August 2012, the national weekly rate of ILI consultations was 85.5 per 100,000 patient population, a notable decrease from the previous week (109.2 per 100,000). Nine 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 73% have been influenza A(H3N2) viruses, 10% influenza B viruses and 7% 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.

Influenza A(H3N2) viruses are the most commonly reported type/sub-type in recent weeks across the southern hemisphere temperate region in Chile, South Africa, and Australia. Pandemic (H1N1) 2009 is the most common influenza virus detected in Paraguay as well as neighbouring areas of southern Brazil, whereas Ecuador, El Salvador, Panama and Peru are reporting mostly influenza B6

National Influenza Centres and laboratories in 67 countries, areas or territories, have reported that for the period 22 July to 4 August 2012, a total of 2,670 specimens were reported as positive for influenza viruses, with 81% being influenza A and 19% influenza B. Of the sub-typed influenza A viruses, 91% were influenza A(H3N2) and 9% were pandemic (H1N1) 2009. Of the characterised influenza B viruses, 70% belong to the B/Victoria lineage and 30% belong to the B/Yamagata lineage8.

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

On 17 August 2012, the US CDC reported an additional 71 cases of influenza infections associated with a variant swine influenza A(H3N2) virus (A(H3N2)v), bringing the total number of cases reported since July 2012 to 224, including 8 hospitalisations10, This variant of the A(H3N2) virus was first detected in humans in July 2011, though only 12 human cases were reported in 2011. The variant virus contains the M gene from the human pandemic (H1N1) 2009 virus, which may confer increased transmissibility to and among humans. The majority of cases have been in persons aged less than 18 years9. All cases in 2012 have been associated with direct or indirect contact with swine, though during 2011 there was some limited human to human transmission reported. Human illness with the variant virus has been generally consistent with signs and symptoms of seasonal influenza, including groups at high risk of complications10, The Centers for Disease Control and Prevention website provides a detailed summary of these variant cases.

6. Data Considerations

The information in this report is reliant on the surveillance sources available to the department. 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 number of lab confirmed influenza detections (not above expected background level)+
AND
No 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
OR
Single 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 area
OR
> 1 outbreaks occurring in equal to or greater than 50% of the influenza surveillance regions within the state or area

+ Small number 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.

Top of pageSyndromic 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.
Further information is available at ASPREN and information regarding the VIDRL coordinated sentinel GP ILI surveillance program.
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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 on the department'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, and
  • 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. 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 #16 ending 19 August 2012. [Accessed 24 August 2012].
2 Victorian Infectious Disease Reference Laboratory, The 2012 Victorian Influenza Vaccine Effectiveness Audit Report, Report 16, 19 August 2012.
3 Western Australia Health, Virus WAtch, Week Ending 19 August 2012.
4 NSW Health, Influenza Weekly Epidemiology Report, 11 to 17 August 2012. [Accessed 24 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. 166, 17 August 2012. [Accessed 24 August 2012]
7 New Zealand Influenza Weekly Update, 13 to 19 August 2012. [Accessed 24 August 2012]
8 WHO, Influenza virus activity in the world, 17 August 2012. [Accessed 24 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 24 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 24 August 2012]

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