Results - Part 8

Other bacterial infections

Other bacterial diseases in the national notifiable disease list are legionellosis, leprosy, invasive meningococcal disease (IMD) and tuberculosis (TB). In 2014, there were 1,942 cases of other bacterial infections notified to the NNDSS, representing less than 1% of all reported cases and similar to the number notified in 2013 (n=1,932). Common objectives for the surveillance of diseases in this section are to monitor their epidemiology and to identify risk groups to accurately target control strategies.

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Legionellosis

Legionella pneumophila, commonly associated with man-made water systems, was the most frequently reported causative species in 2014.

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.²² The species most commonly associated with human disease in Australia are Legionella pneumophila and L. longbeachae. Legionella bacteria are found naturally in low levels in the environment. In the absence of effective environmental treatments Legionella organisms can proliferate in air conditioning cooling towers, hot water systems, showerheads, spa pools, fountains, commercial potting mix and other decomposing material such as bark and sawdust.^166–169 Legionella is generally transmitted to humans through contaminated water or dust aerosols.

Epidemiological situation in 2014

In 2014, there were 424 notifications of legionellosis, representing a rate of 1.8 per 100,000. Notifications declined by 17% following an outbreak-related peak in 2013 (n=508) (Figure 103).

Figure 103: Notifications of legionellosis, Australia, 2009 to 2014, by species and year

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In 2014, data on the causative species were available for 85% (n=362) of notifications reported. Of those with a known causative, the most frequently reported causative species were L. pneumophila (54%, 195), followed by L. longbeachae (45%, 164). A single notification of L. sainthelensi and 2 notifications of L. micdadei were also reported (Table 24). Serogroup information was reported for 62% (120/195) of L. pneumophila notifications and 11% (18/164) of L. longbeachae notifications. Of these, 98% (117/120) of L. pneumophila notifications were typed to L. pneumophila serogroup 1, 1 notification was serogroup 2 and 2 were mixed. All L. longbeachae notifications were typed to L. longbeachae serogroup 1.

Table 24: Notifications, notification rates and deaths for legionellosis, Australia, 2014, by species and state or territory

Species	State or territory								Aust.	Deaths
	ACT	NSW	NT	Qld	SA	Tas.	Vic.	WA
* 3 deaths. † 2 deaths. ‡ 1 death.
L. longbeachae	1	17†	4	16	19	5	9	93*	164	5
L. pneumophila	1	41	3‡	45‡	20†	2	60	23†	195	6
L. micdadei	0	1‡	0	0	0	0	1	0	2	1
L. sainthelensi	0	0	0	0	1	0	0	0	1	0
Unknown species	0	11	0	33	0	1	17‡	0	62	1
Total	2	70	7	94	40	8	87	116	424	13

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Over the period of 2009 to 2014, the number of notified cases of L. pneumophila ranged from 114 to 228 per year, whilst notified cases of L. longbeachae ranged from 144 to 215 per year (Figure 103). When compared with 2013, notifications of L. pneumophila declined by 14% and L. longbeachae by 24%.

In 2014, mortality data were available for 78% (n=329) of notifications. Of these, 4% (13/329) were reported to have died due to legionellosis and this was similar to the number of deaths reported in previous years. The majority of deaths were attributed to infection with L. pneumophila (46%, 6/13) (Table 24). Over the last 6 years (2009 to 2014) the mortality data of legionellosis notification has improved with the proportion of cases reported with death information increasing from 49% in 2009 to 78% in 2014.

Geographic distribution

In 2014, jurisdictional-specific rates of legionellosis varied from 0.5 per 100,000 in the Australian Capital Territory to 4.5 per 100,000 in Western Australia (Table 5).

In 2014, L. pneumophila was the most notified causative species in New South Wales, Queensland, South Australia and Victoria, while L. longbeachae was more frequently notified in the Northern Territory, Western Australian and Tasmania. The Australian Capital Territory reported and an equal number of notifications of both species. The most frequent species annually reported by each jurisdiction can vary between L. pneumophila and L. longbeachae. However, generally Western Australia and Northern Territory tend to report more L. longbeachae notifications, while New South Wales, Queensland, South Australia and Victoria tend to report more L. pneumophila notifications. The Australian Capital Territory and Tasmania tend to report only a small number of notifications each year; therefore, they have no obvious trend in the most frequent causative species.

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Age and sex distribution

In 2014, males accounted for the majority (65%) of the notifications resulting in a male to female ratio of 1.8:1. There were no notifications in people under the age of 15 years. In males, the highest notification rates were observed in those aged 80–84 years (14.3 per 100,000) and 85 years and over (10.3 per 100,000). While in females, the highest notification rates were observed in those aged 65–69 years and 80–84 years age groups (both 4.8 per 100,000) (Figure 104).

Figure 104: Notification rate for legionellosis, Australia, 2014, by age group, sex and species

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The ages of the 13 cases reported to have died due to legionellosis in 2014 ranged between 57 to 83 years (median 75 years); 12 deaths were male and 1 was female. In 2014, the demographic profile of legionellosis remained consistent with the recognised epidemiology of the disease.^22,170,171

Seasonality

In 2014, diagnoses of legionellosis were highest in October, with 44 notified cases. The diagnosis of L. pneumophila peaked in April–May (24 cases each month), and the diagnosis of L. longbeachae peaked in October (n=22). From 2009 to 2013, the diagnosis of L. pneumophila commonly occurred in the autumn and summer months, except for 2013 when diagnoses peaked at the end of winter. In the same period, the diagnosis of L. longbeachae more commonly occurred in winter and spring. (Figure 105).

Figure 105: Notifications of legionellosis, Australia, 2009 to 2014, by month and year of diagnosis and species

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Place of acquisition

In 2014, a place of acquisition was reported for 86% (n=363) of legionellosis notifications. Of these, 92% (334) were reported as acquired within Australia and 8% (29) were reported as acquired overseas. Of the overseas acquired notifications, Indonesia (17%, 5/29), the United States of America (10%, 3/29) and Thailand (10%, 3/29) were the most commonly reported places of acquisition.

Outbreaks

In 2014, there were 5 outbreaks of L. pneumophila reported to the NNDSS.

In South Australia, there was an outbreak of 6 cases of legionellosis caused by L. pneumophila serogroup 1. All cases lived or worked within the Adelaide central business district (CBD). During the environmental investigation several cooling towers in the Adelaide CBD were identified as reservoirs of L. pneumophila serogroup 1 and were subsequently decontaminated.

In Victoria, there were 4 outbreaks, involving a total of 17 cases. None of these outbreaks were linked to overseas sources and none of the cases linked to outbreaks died due to their infection.

One of the outbreaks involved a total of 10 cases and included 4 separate clusters. There were 3 environmental detections from cooling towers associated with the outbreak; however, none of the environmental samples matched the Legionella strain isolated from the clinical samples.

Another outbreak involved 3 linked cases, all of whom had either visited or worked at the Melbourne Airport. Despite extensive sampling and testing, no environmental detections were found for this outbreak.

The remaining 2 outbreaks involved 2 cases in each outbreak. One of these outbreaks was associated with a common geographical link, but no environmental detections were found. The other outbreak was linked to a workplace at the port of Melbourne. An environmental detection was found in a cooling tower in the port of Melbourne area but this environmental sample did not contain the same Legionella strain as isolated from the clinical samples.

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Leprosy

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 in migrants from leprosy-endemic countries and Indigenous populations. The incidence of leprosy worldwide is declining due to various factors including economic development, bacille Calmette Guérin (BCG) immunisation and high coverage with multi-drug therapy.²² 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.¹⁷² People at-risk are generally in close and frequent contact with leprosy patients or living in countries where the disease is more common. Leprosy is curable and once a person with leprosy begins appropriate treatment, they quickly become non-infectious.

Epidemiological situation in 2014

In 2014, a total of 9 cases of leprosy were notified (4 female, 5 male), representing a rate of less than 0.1 per 100,000. There were 5 cases notified in Western Australia, and 1 each in Victoria, South Australia, Queensland and New South Wales. Cases ranged in age from 17 to 75 years, with a median age of 45 years. Two cases were reported as being Indigenous. The remaining 7 cases were reported as being non-Indigenous and as having acquired the infection overseas. Cases were reported as being from India (n=2), Sri Lanka (n=1), the Philippines (n=1), Samoa (n=1) and the overseas country of acquisition was unknown for 2 cases. Since 1995, annual notifications of leprosy have ranged from 2 to 15 cases per year (Figure 106).

Figure 106: Notifications of leprosy, Australia, 1995 to 2014, by year and Indigenous status

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Meningococcal disease (invasive)

IMD is caused when the bacterium Neisseria meningitidis enters a normally sterile site, usually the blood (septicaemia), cerebrospinal fluid (meningitis) or both. Asymptomatic respiratory tract carriage of meningococci is present in 5% to 10% of the population and prevalence may be higher when groups of people occupy small areas of any space.^22,32 The disease is transmitted via respiratory droplets and has an incubation period of between 2 and 10 days, commonly 3 to 4 days. ^22,173 It occasionally causes a rapidly progressive serious illness, most commonly in previously healthy children and young adults. Globally, serogroups A, B, C, X, W135 and Y commonly cause invasive disease.¹⁷⁴ Historically, N. meningitidis serogroups B and C have been the major cause of IMD in Australia.

Epidemiological situation in 2014

In 2014, there were 170 cases of IMD reported to the NNDSS, representing a rate of 0.7 per 100,000 population. This was an increase of 14% compared with 2013 (n=149), but less than the number of cases notified between 2003 and 2012 (range 556 to 223 cases) (Figure 107). This rise in IMD cases was due to infections caused by serogroup B.

Figure 107: Notifications of invasive meningococcal disease, Australia 2003 to 2014, by selected serogroup and year

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The majority of cases notified in 2014 (99%, n=168) met the case definition as a confirmed case, being diagnosed based on laboratory definitive evidence, or laboratory suggestive evidence and clinical evidence.¹⁷³ A small number of cases (n=2) were reported as probable and diagnosed based on clinical evidence only.

In 2014, all states and territories reported cases of IMD (Table 1), with notification rates ranging from 0.4 per 100,000 in Tasmania to 2 per 100,000 in South Australia (Table 25). Mortality data were available for 74% (126/170) of cases. Of these, 8 cases were reported as having died from IMD, including 7 from infection with serogroup B organisms, and 1 from infection with serogroup Y organisms (Table 25). Six of the deaths associated with IMD infection caused by serogroup B organisms occurred in children less than 5 years of age and 1 in a teenager 17 years of age. The 1 death caused by a serogroup Y organism occurred in an adult over 85 years of age.

Table 25: Notifications of invasive meningococcal disease and deaths due to invasive meningococcal disease, Australia, 2014, by serogroup and state or territory

Serogroup	State or territory								Aust.	Deaths
	ACT†	NSW†	NT	Qld	SA	Tas.	Vic.	WA
* Unknown includes notifications where serogroup was non-groupable or not grouped. Not grouped is when no serogroup is available and non-groupable is where the serogroup is reported by the reference laboratory as a non-groupable strain. † Conjunctival IMD cases are also reported under the local case definition, and reported to the national dataset by the jurisdiction. Conjunctival cases cannot be distinguished from invasive cases in the national dataset.
B	1	23	3	30	34	1	27	13	132	7
C	0	0	0	1	0	0	0	2	3	0
W135	0	7	0	3	0	1	4	2	17	0
Y	1	7	0	2	0	0	1	1	12	1
Unknown*	0	1	0	4	0	0	1	0	6	0
Total	2	38	3	40	34	2	33	18	170	8
Rate per 100,000	0.5	0.5	1.2	0.8	2.0	0.4	0.6	0.7	0.7	0

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Age and sex distribution

More males (53%, n=90) than females (47%, n=80) were notified with IMD in 2014. Proportionally, 72% (n=122) of all cases reported were less than 25 years of age, of which half were children less than 5 years of age (n=61). The highest notification rate in 2014 for both males and females was in the 0–4 years age group (3.4 per 100,000) with a second peak in adolescents (15–19 years of age) (Figure 108).

Figure 108: Notification rate for invasive meningococcal disease, Australia, 2014, by age group and sex (n=170)

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Serogroup analysis

Data on serogroup were available for 96% (n=164) of cases in 2014, of which 80% (132) were caused by serogroup B organisms, 10% (17) by serogroup W135, 7% (12/164) by serogroup Y and 2% (3) by serogroup C (Table 25). Cases caused by serogroup Y (n=12) were slightly lower compared with 2013 (n=14), but were higher than the average of 10 cases seen in the previous 10 years (2004–2013). Notifications of IMD caused by serogroup C organisms continue to decrease with 3 cases notified in 2014 compared with 8 in 2013 (Table 25) and representing a 98% decrease since the introduction of the meningococcal C vaccine on the NIP in 2003.

All 3 cases of IMD due to serogroup C organisms notified in 2014 were under the age of 25 years. Two cases were in the 0–4 years age group, and 1 was in the 20–24 years age group. Age-specific rates of serogroup C infections have remained below 0.2 cases per 100,000 since 2010.

Serogroup B accounted for the majority of cases across all age groups including those aged less than 25 years. Compared with 2013, serogroup B rates were relatively stable in all age groups except the 5–9 years and 20–24 years age groups, which displayed a 2-fold and 2.4-fold increase respectively (Figure 109).

Figure 109: Notification rate for serogroup B invasive meningococcal disease, Australia, 2009 to 2014, by year and selected age groups

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An increase in notifications of serogroup W135 was evident in 2014 (n=17) with notifications nearly 2 times higher than the annual average of the previous 5 years. There were 17 cases of W135 reported in 2014 compared with 12 cases in 2013 and 7 cases in 2012.

Vaccination status

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

Of the 3 cases of IMD caused by serogroup C organisms reported in 2014, 2 were less than 12 months of age and therefore not eligible for vaccination, and 1 was eligible for vaccination (21 years) but was reported with an unknown vaccination status.

Seasonality

In 2014, an average of 14 cases of IMD were reported monthly, with a range of 7 to 26 cases. A clear seasonal pattern was apparent in 2014, with the highest number of notifications reported in spring. The 2014 season peaked in September with 26 cases reported and was later than the seasonal pattern displayed in the previous 5 years (2009 to 2013), in which notifications peaked in mid to late winter (Figure 110). Consistent with the previous 5 years, the 2014 seasonal trend was more obvious in cases 5 years of age or over compared with those less than 5 years of age.

Figure 110: Notifications of invasive meningococcal disease, Australia, 2009 to 2014, by month and year and age group

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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 2014.¹⁷⁵ The latest data from AMSP show that 12% of isolates tested were fully sensitive and 88% demonstrated decreased susceptibility to the penicillin group of antibiotics. No isolates tested in 2014 exhibited resistance to penicillin. All tested IMD isolates were susceptible to ceftriaxone and ciprofloxacin, and 2 isolates were resistant to rifampicin.

Discussion

In Australia, IMD has remained at its lowest levels since the national notification commenced in 1991. The reduction has been seen most considerably in disease caused by serogroup C, but declines in disease caused by serogroup B are also evident.

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 when 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. ¹⁷⁶

Epidemiological situation in 2014

In 2014, a total of 1,339 cases of TB were notified to the NNDSS representing a rate of 5.7 per 100,000. This was an increase on the rate of 5.5 per 100,000 (n=1,263) reported in 2013, but less than the preceding 5-year mean (2009 to 2013) of 5.9 per 100,000. Australia has achieved good TB control and has maintained low rates of TB since the mid 1980s (Figure 111).

Figure 111: Notification rate for tuberculosis, Australia, 1960 to 2014, by year

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Geographic distribution

New South Wales (n=472), Victoria (n=448), Queensland (n=165) and Western Australia (n=139) accounted for 91% of all cases of TB diagnosed in Australia. The Northern Territory (11.4 per 100,000), the Australian Capital Territory (7.8 per 100,000), Victoria (7.7 per 100,000) and New South Wales (6.3 per 100,000) all reported a rate higher than the national notification rate. In 2014, the Northern Territory, South Australia and Western Australia reported lower notification rates than the previous year. All the other states and territories reported an increase on the previous year. Notifications and rates of TB by state or territory are presented in Table 6.

Age and sex distribution

Overall, the age groups with the highest notification rates were in the 25–29 years and 85 years or over age groups (both 11.4 per 100,000), followed by the 30–34 years age group (10.1 per 100,000). The highest age and sex specific rates were observed in men in the 85 years or over (22.4 per 100,000) and women in the 25–29 years age groups (13.3 per 100,000) (Figure 112). Males accounted for 53% of the TB notifications in 2014.

Figure 112: Notification rate for tuberculosis, Australia, 2014, by age group and sex

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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.^177,178

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. It is contraindicated in HIV infected persons.¹⁷⁹ 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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