Australia’s notifiable disease status, 2013: Annual report of the National Notifiable Diseases Surveillance System: Part 9

The National Notifiable Diseases Surveillance System monitors the incidence of an agreed list of communicable diseases in Australia. This report analyses notifications during 2013.

Page last updated: 16 October 2015

Results - Part 2 continued

Other bacterial infections

Legionellosis

  • A total of 505 cases of legionellosis were notified in 2013.
  • Compared with 2012, notifications of legionellosis increased by 32% in 2013.
  • Legionella pneumophila, commonly associated with man-made water systems, was the most frequently reported causative species in 2013.
  • Five clusters and 3 outbreaks of legionellosis were reported in 2013.

Legionellosis is an environmentally acquired pneumonia caused by the bacteria Legionella. It can take the form of either Legionnaires’ disease, a severe form of infection of the lungs, or Pontiac fever, a milder influenza-like illness.21 The species most commonly associated with human disease in Australia are Legionella pneumophila and Legionella longbeachae. Legionella bacteria are found naturally in low levels in the environment. In the absence of effective environmental treatments Legionella organisms can breed in air conditioning cooling towers, hot water systems, showerheads, spa pools, fountains, commercial potting mix and other decomposing material such as bark and sawdust.145–148 Legionella is generally transmitted to humans through contaminated water or dust aerosols.

Epidemiological situation in 2013

There were 505 notifications of legionellosis in 2013, representing a rate of 2.2 notifications per 100,000. Compared with the previous reporting period notifications of legionellosis increased in 2013 by 32% and were the highest since 2008 (Figure 88). It is likely that at least half of the increase in 2013 can be attributed to the outbreak at the Wesley Hospital in Queensland and the subsequent increase in serological testing during that period.149 This outbreak received significant media coverage and resulted in Queensland issuing public health alerts to the community.

Figure 88: Notified cases of legionellosis, Australia, 2008 to 2013, by year of diagnosis and species

line and bar chart. A link to a text description follows.

Text version of Figure 1 (TXT 88 KB)

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In 2013, data on the causative species were available for 88% (n=444) of notifications reported. Proportionally, there were slightly more notifications of Le. pneumophila (51%) than Le. longbeachae (48%). A single notification of Le. anisa and 2 notifications of Le. micdadei were also reported (Table 21). Serogroup information was only reported for 70% of Le. pneumophila notifications and 17% of Le. longbeachae notifications. Of these, 91% of Le. pneumophila notifications were typed to Le. pneumophila serogroup 1 and all Le. longbeachae notifications were typed to Le. longbeachae serogroup 1.

Table 21: Notified cases, rates and deaths for legionellosis, Australia, 2013, by species and state or territory
Species ACT NSW NT Qld SA Tas. Vic WA Aust. Deaths due to legionellosis
* 3 deaths.

† 2 deaths.

‡ 1 death.
Le. longbeachae
0
38
4
45
31
3
13
79
213
2
Le. pneumophila
1
54*
1
73*
32
3
50
14
228
12
Le. anisa
0
0
0
1
0
0
0
0
1
0
Le. micdadei
0
0
0
0
0
0
2
0
2
0
Unknown species
0
13
1
46
0
0
1
0
61
1
Total
1
105
6
165
63
6
66
93
505
15
Rate (per 100,000)
0.3
1.4
2.5
3.5
3.8
1.2
1.2
3.7
2.2

Over the period 2008 to 2013, the notified cases of Le. pneumophila ranged from 101 to 228, whilst notified cases of Le. longbeachae ranged from 144 to 213 (Figure 89). When compared with 2012, notifications of Le. pneumophila increased by 40% and Le. longbeachae by 13%.

In 2013, mortality data was available for 71% (n=358) of notifications. Of these, 4% (n=15) were reported to have died due to legionellosis. This proportion was equivalent to the proportion of notifications reported to have died in 2012 (3%, n=11). The majority of deaths were attributed to infection with Le. pneumophila (80%, n=12) (Table 21). Over the last 5 years (2008 to 2013) the mortality data of legionellosis notification has improved with the proportion of cases reported with death information increasing from 49% in 2008 to 71% in 2013.

Figure 89: Notification rate for legionellosis, Australia, 2013, by age group and sex and species

line and bar chart. A link to a text description follows.

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Geographic description

In 2013, jurisdictional-specific rates of legionellosis varied from 0.3 per 100,000 in the Australian Capital Territory to 3.8 per 100,000 in South Australia (Table 21).

In 2013, Le. pneumophila was the most notified infecting species in the Australian Capital Territory, New South Wales, Queensland, South Australia and Victoria, while Le. longbeachae was more common in the Northern Territory and Western Australia. Tasmania reported and equal number of notifications of both species. The geographic distribution in 2013 differed from 2012 in that Le. pneumophila was the most commonly notified species in only New South Wales, Tasmania and Victoria, with Le. longbeachae being more commonly notified in all other remaining states and territories.

Age and sex distribution

In 2013, legionellosis was predominantly seen in older males. Males accounted for the majority (54%, n=271) of the notifications resulting in a male to female ratio of 1.2:1. There were no notifications in people under the age of 10 years. The highest age and sex specific rates were observed in men and women aged 75–79 years or over at 8.7 per 100,000 and 8.6 per 100,000, respectively (Figure 89). The ages of the 15 cases reported to have died due to legionellosis in 2013 ranged between 38 and 96 years (median 72 years); 11 deaths were male and 4 were female. In 2013, the demographic profile of legionellosis remained consistent with the recognised epidemiology of the disease.21,150,151

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Analysis by infecting species and age group identified that 93% of Le. longbeachae notifications were reported in persons aged 40 years or over and was the predominant species reported in the 75–79 years age groups (4.6 per 100,000). Similarly, 85% of notified Le. pneumophila infections were in persons aged 40 years or over and was the predominant species in the 85 years or over age group (3.2 per 100,000).

Seasonality

In 2013, diagnoses of legionellosis were highest in September, with 60 notified cases (Figure 90). In 2013, the seasonal pattern of Le. pneumophila and Le. longbeachae differed from the seasonal patterns seen in the previous 5 years. From 2008 to 2012, the diagnosis of Le. pneumophila commonly occurred in the autumn and summer months, whilst a diagnosis of Le. longbeachae was more common in the spring months. In 2013, the diagnosis of both species peaked in winter, with 70 Le. pneumophila cases and 71 Le. longbeachae cases notified in June, July and August (Figure 90). It is unclear why this change in seasonality occurred, but it may be the result of the increase in legionellosis testing in Queensland between June and September 2013 following the Wesley Hospital outbreak.

Figure 90: Notified cases of legionellosis, Australia, 2008 to 2013, by month and year of diagnosis and species

line and bar chart. A link to a text description follows.

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Place of acquisition

In 2013, a place of acquisition was reported in 80% (n=402) of legionellosis notifications. Of these, 94% (n=379) were reported to be acquired within Australia and 6% (n=23) were reported to be acquired overseas. Of the overseas acquired notifications, Thailand (17%, n=4) and Indonesia (13%, n=3) were the most commonly reported places of acquisition.

Outbreaks

In 2013, there were 5 clusters and 3 outbreaks of legionellosis notified to the NNDSS. All were attributed to Le. pneumophila serogroup 1 and occurred in 3 jurisdictions; Queensland, South Australia and Victoria.

There was 1 outbreak reported in Queensland. On 5 June 2013, the Wesley Hospital notified Queensland Health of 2 legionellosis cases, one resulting in death. Environmental investigations identified the most probable source of infection for this outbreak of Le. pneumophila was contamination of the hospitals heated water systems.149

In 2013, Victoria reported 4 clusters and 2 outbreaks, involving a total of 26 cases, and South Australia reported 1 cluster involving 12 cases. The sources of infection of these clusters and outbreaks were not determined.

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Leprosy

  • A total of 13 cases of leprosy were notified in 2013, maintaining a notification rate of less than 0.1 per 100,000.

Leprosy is a chronic infection of the skin and peripheral nerves with the bacterium Mycobacterium leprae. Leprosy is an uncommon disease in Australia with the majority of cases occurring among migrants from leprosy endemic countries. The incidence of leprosy worldwide is declining due to various factors including economic development, bacillus Calmette-Guérin (BCG) immunisation and high coverage with multi-drug therapy.21 Leprosy is not a highly infectious disease and is typically slow to progress to a symptomatic stage. The incubation period for leprosy is about 5 years; however, it can take as long as 20 years for symptoms to appear.152 People at risk are generally in close and frequent contact with leprosy patients or living in countries where the disease is more common. New treatments mean the disease is now curable and once a person with leprosy begins appropriate treatment, they quickly become non-infectious.

In January 2014, the NSC redefined the diagnosis date methodology used to count leprosy cases due to the considerable amount of time that can elapse between the initial infection, the onset of symptoms and the subsequent diagnosis; and that in many of Australia’s leprosy cases the infection was acquired prior to the case migrating to Australia. The diagnosis date is now derived from the ‘notification received date’ field rather than the earliest date recorded in either the ‘true onset date’, ‘specimen date’, ‘notification date’ or ‘notification received date’ fields. This definition also aligns with the methodology to count tuberculosis cases in Australia. Note that the new methodology has been applied retrospectively to the historical notification data described in this report. Therefore, data presented in this report may not correspond with NNDSS leprosy data published prior to January 2014.

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Epidemiological situation in 2013

In 2013, a total of 13 cases of leprosy were notified (8 male, 5 female), representing a rate of 0.1 per 100,000. Cases were spread across all jurisdictions except Tasmania (Table 4). Cases ranged in age from 28 to 56 years, with a median age of 36 years. Only 1 case was recorded as Indigenous. Since 1993, annual notifications of leprosy have ranged from 4 to 13 cases per year (Figure 91).

Figure 91: Notified cases of leprosy, Australia, 1993 to 2013, by year of diagnosis and Indigenous status

bar chart. A link to a text description follows.

Text version of Figure 91 (TXT 1 KB)

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Meningococcal disease (invasive)

Meningococcal disease is caused by the bacterium Neisseria meningitidis, and invasive disease occurs when bacteria enter a normally sterile site, usually the blood (septicaemia), cerebrospinal fluid (meningitis) or both. Asymptomatic respiratory tract carriage of meningococci is present in 5%–10% of the population and prevalence may be higher when groups of people occupy small areas of any space.21, 50 The disease is transmitted via respiratory droplets and has an incubation period of between 1 and 10 days, more commonly 3 to 4 days.50,153 It occasionally causes a rapidly progressive serious illness, most commonly in previously healthy children and young adults. Globally, serogroups A, B, C, W135 and Y most commonly cause disease.21 Historically, N. meningitidis serogroups B and C have been the major cause of invasive meningococcal disease (IMD) in Australia.

Epidemiological situation in 2013

In 2013, there were 149 cases of IMD representing a rate of 0.6 per 100,000. This was a decrease of 33% compared with 2012 (n=222) and the lowest number of cases notified over the previous 10 years (Figure 92).

Figure 92: Notified cases of invasive meningococcal disease, Australia, 2002 to 2013, by year of diagnosis and serogroup

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Most cases (n=145) notified in 2013 met the case definition as a confirmed case, that is, diagnosed based on laboratory definitive evidence, or laboratory suggestive evidence and clinical evidence.154 A small number of cases (n=4) met the case definition as a probable case, that is, diagnosed based on clinical evidence only.

Data on serogroup were available for 94% (n = 140) of cases in 2013; 76% of which were caused by serogroup B organisms, 10% by serogroup Y, 6% by serogroup C and 9% by serogroup W135 (Table 22). The number of cases of IMD caused by serogroup B notified in 2013 was lower than in any of the preceding 10 years. Notifications of IMD caused by serogroup C organisms decreased by 27.3% from the previous year (n= 11). The number of serogroup Y cases notified in 2013 (n=14) was consistent with 2012 (n=15) but higher than the average of the previous 10 years (2003–2012) of 9.6 cases. Serogroup Y infections account for a small but increasing proportion of total IMD notifications, increasing from 3% of cases notified in 2009 to 4% in 2010, 5% in 2011 and 7% in 2012. Since the introduction of the meningococcal C vaccine on the NIP in 2003, notifications caused by serogroup C organisms have decreased by 94% with fewer than 10 cases reported annually for the past 3 years.

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Table 22: Notified cases of invasive meningococcal disease and deaths due to invasive meningococcal disease, Australia, 2013, by serogroup and state or territory
  ACT NSW NT Qld SA Tas. Vic. WA Aust. Deaths due to IMD
B
2
27
2
25
18
2
19
11
106
2
C
0
3
0
2
0
0
1
2
8
1
W135
0
6
0
3
1
0
1
1
12
0
Y
1
8
0
2
1
0
1
1
14
1
Unknown
0
4
0
1
0
1
3
0
9
1
Total
3
48
2
33
20
3
25
15
149
5
Rate (cases per 100,000)
0.8
0.6
0.8
0.7
1.2
0.6
0.4
0.6
0.6

Mortality data were available for 60% (n=89) of cases reported to the NNDSS in 2013. There were 5 cases reported as having died from IMD, including two due to serogroup B, one due to serogroup C, one due to serogroup Y and 1 death due to an unknown serogroup (Table 22).

The serogroup C related death occurred in an unvaccinated person in the 50–54 years age group. Of the deaths due to serogroup B organisms, 1 child was less than 5 years of age, and the other was in the 15–19 years age group. The unknown serogroup death occurred in the 45–49 years age group and the serogroup Y related death occurred in the 85 years or over age group.

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Geographic description

All jurisdictions aligned with the national case definition for IMD, except the Australian Capital Territory and New South Wales where conjunctival cases were also reportable under the local case definition and reported nationally. Conjunctival cases cannot be distinguished from invasive cases in the national dataset.

In 2013, cases of IMD were reported from all states and territories, ranging from two cases in the Northern Territory to 48 cases from New South Wales (Table 22). Jurisdictional specific rates ranged from 0.6 per 100,000 in Tasmania to 1.8 per 100,000 in South Australia.

Age and sex distribution

More males than females were reported with IMD in 2013, with a male to female ratio of 1.3:1. Proportionally, 40% of all cases (n=102) reported were less than 25 years of age, of which those less than 5 years of age made up almost half (n=47). Specifically, the 0–4 years age group had the highest rate of 6.1 per 100,000 followed by the 15–19 years age group (3.7 per 100,000) and the 20–24 years age group (1.7 per 100,000) (Figure 93).

Figure 93: Notification rate for invasive meningococcal disease, Australia, 2013, by age group and sex

bar chart. A link to a text description follows.

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Serogroup B accounted for the majority of cases across all age groups including those aged less than 25 years. While the age-specific rates of serogroup B infection in 2013 remain high compared with other serogroups they continue to trend downward across all age groups (Figure 94).

Figure 94: Notification rate for serogroup B invasive meningococcal disease, Australia, 2008 to 2013, by year of diagnosis and select age groups

line chart. A link to a text description follows.

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Of the 8 cases of IMD due to serogroup C notified in 2013 only 3 were among children and young adults aged less than 25 years of age, and therefore eligible for vaccination. None of the cases were in the 0–4 years of age group. Age-specific rates have been maintained at very low levels in 2013, with no age group exceeding 0.1 cases per 100,000 in 2013 (Figure 95).

Figure 95: Notification rate for serogroup C invasive meningococcal disease, Australia, 2008 to 2013, by select age groups

line chart. A link to a text description follows.

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Seasonality

An average of 12 cases of IMD was reported monthly in 2013, with a monthly range of 5 to 21 cases. A clear seasonal pattern was apparent, with the highest number of notifications reported in the winter months. This was consistent with the normal seasonal pattern of this disease (Figure 96). The seasonal trend was more marked in cases aged 5 years or over.

Figure 96: Notified cases of invasive meningococcal disease, Australia, 2008 to 2013, by age group and month and year of diagnosis

line and bar chart. A link to a text description follows.

Text version of Figure 96 (TXT 1 KB)

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Susceptibility

The Australian Meningococcal Surveillance Program (AMSP) was established in 1994 for the purpose of monitoring and analysing isolates of N. meningitidis from cases of IMD in Australia. The program is undertaken by a network of reference laboratories in each state and territory, using standardised methodology to determine the phenotype (serogroup, serotype and serosubtype) and the susceptibility of N. meningitidis to a core group of antibiotics.

Annual reports of the AMSP are published in CDI with the most recent report published for 2013.76 The latest data from AMSP show that 79% of isolates tested demonstrated decreased susceptibility to the penicillin group of antibiotics, and no isolates exhibited resistance to penicillin. All IMD isolates tested were susceptible to ceftriaxone; ciprofloxacin and rifampicin.

Vaccination

From 2003, meningococcal C vaccine has been available for infants aged 12 months as a part of the childhood immunisation schedule funded under the NIP. Additionally, a catch-up program provided access to the meningococcal C vaccine for children and adolescents born between 1984 and 2001.

Of the 8 cases of IMD caused by serogroup C organisms reported in 2013, three were eligible for vaccination of which 1 case was reported as vaccinated and the remaining two were of unknown vaccination status.

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Discussion

In Australia, IMD has reached its lowest levels since the national notification commenced in 1991. The reduction has been seen most considerably in disease caused by serogroup C; however, declines in disease caused by serogroup B are also evident. In 2013, serogroup Y continued to account for an increasing proportion of notified cases. This small but increasing trend in serogroup Y infections will continue to be monitored.

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Tuberculosis

  • 1,265 cases of tuberculosis were notified in 2013.

Tuberculosis (TB) is an infection caused by the bacterium Mycobacterium tuberculosis. TB is transmitted by airborne droplets produced by people with pulmonary or respiratory tract TB during coughing or sneezing. While Australia has one of the lowest rates of TB in the world, the disease remains a public health issue, particularly in Australia’s overseas-born and Indigenous communities.155

Epidemiological situation in 2013

In 2013, a total of 1,265 cases of TB were notified to the NNDSS representing a rate of 5.5 per 100,000. Australia has achieved good TB control and has maintained low rates of TB since the mid-1980s; however, in the decade leading up to 2011 a steady increase in incidence was observed. Contrary to this increasing trend the 2012 and 2013 rates have both decreased and may be an indication that incidence is beginning to plateau or even decrease (Figure 97).

Figure 97: Notification rate for tuberculosis, Australia, 1960 to 2013, by year of diagnosis

line chart. A link to a text description follows.

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In 2013, 2.4% of TB notifications were recorded as being Indigenous. This represents a rate of 5.0 per 100,000 in Aboriginal and Torres Strait Islander peoples.

Geographic description

New South Wales (n=440), Victoria (n=383), Queensland (n=156) and Western Australia (n=150) accounted for 89% of all cases of TB diagnosed in Australia. The Northern Territory (17.0 per 100,000), Victoria (6.7 per 100,000), Western Australia (6.0 per 100,000) and New South Wales (5.9 per 100,000) all recorded a rate higher than the national notification rate.

In 2013, the Northern Territory, Tasmania and Victoria all recorded higher notification rates than the previous year. All the other states and territories reported a decrease on the previous year, with the greatest decrease being reported by South Australia (18% decrease).

Age and sex distribution

In 2013, 50% of all TB notifications were seen in people aged 20–39 years. Overall, the age group with the highest notification rate was the 25–29 years age group (12.1 per 100,000) and the highest age and sex specific rates were observed in men aged 85 years or over (16.6 per 100,000) and women aged 25–29 years (11.0 per 100,000)0 (Figure 98).

Figure 98: Notification rate for tuberculosis, Australia, 2013, by age group and sex

bar chart. A link to a text description follows.

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Males accounted for more than half (57%) of the TB notifications, resulting in a male to female ratio of 1.3:1.

Vaccination

The BCG vaccine was first introduced for protection against tuberculosis in the 1920s and despite variable evidence on the efficacy of the vaccine it remains the only vaccine in use for TB today.156,157

According to national guidelines developed by Australia’s National Tuberculosis Advisory Committee, BCG vaccination is recommended for: Aboriginal and Torres Strait Islander neonates in communities with a high incidence of TB; neonates and children under 5 years of age who will be travelling to or living in countries or areas with a high prevalence of TB for extended periods; and neonates born to parents with leprosy or a family history of leprosy.

BCG vaccination is not recommended for general use in the Australian population or for most health care workers and is contraindicated in HIV infected persons.158 Note that BCG immunisation practices may vary between states and territories due to differences in jurisdiction-specific TB vaccination policies and population demographics.

Enhanced surveillance data sets

Enhanced data are collected on all cases of TB. Further analyses, including identification of risk groups and reporting on treatment outcomes, can be found in the TB annual report series also published in CDI.

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