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Results, cont'd

Other bacterial infections

Legionellosis, leprosy, meningococcal infection and tuberculosis were notifiable in all states and territories in 2010 and classified as ‘other bacterial infections’ in the NNDSS. A total of 1,866 notifications were included in this group in 2010, which accounted for less than 1% of all the notifications to NNDSS, a decrease in cases and a similar proportion as in 2009 (n = 1,911 and 1% of total).

Legionellosis

Legionellosis, caused by the bacterium Legionella, can take the form of either Legionnaires’ disease, a severe form of infection of the lungs or Pontiac fever, a milder influenza-like illness. The species that are most commonly associated with human disease in Australia are L. pneumophila and L. longbeachae. Legionella bacteria are found naturally in low levels in the environment. In the absence of effective environmental treatment Legionella organisms can breed to high numbers in air conditioning cooling towers, hot water systems, showerheads, spa pools, fountains or potting mix.

Infections caused by any Legionella species are notifiable, provided they meet the national surveillance case definition. There were 298 notified cases of legionellosis reported in 2010, giving a national rate of 1.3 per 100,000 and consistent with the 302 cases reported in 2009 (Figure 68). Rates for states and territories ranged from 0.9 per 100,000 in Queensland to 2.4 in Western Australia in 2010.

Figure 68: Notified cases of legionellosis, Australia, 2005 to 2010, by month and year and state or territory

Data on the causative species were available for 91% of cases; the majority were L. longbeachae (46%) and L. pneumophila (45%) (Table 17).

Table 17: Cases of legionellosis, Australia, 2010, by species and state or territory

Species	State or territory								Aust	Total %
	ACT	NSW	NT	Qld	SA	Tas	Vic	WA
Legionella longbeachae	0	47	2	17	20	1	5	46	138*	46
Legionella pneumophila	0	39	1	18	9	5	53	8	133†	45
Legionella bozemanii	0	0	0	0	0	0	1	0	1	0.3
Unknown species	4	7	0	7	0	0	8	0	26	9
Total	4	93	3	42	29	6	67	54	298	100

* Two deaths.

† Five deaths.

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Historically, there have been differences in the geographic distribution of L. longbeachae and L. pneumophila, with L. longbeachae making up the majority of notifications from South Australia and Western Australia, while L. pneumophila has been the most common infecting species in the eastern states (Queensland, New South Wales and Victoria). However, similar to 2009, L. longbeachae was notified more frequently than L. pneumophila in New South Wales and almost as frequently in Queensland in 2010.

Six of the 8 L. pneumophila cases reported in Western Australia in 2010 acquired their infections in Bali, Indonesia and five of these cases stayed at a particular hotel in Kuta, Bali. An additional 4 cases associated with this hotel or a nearby exposure source were identified in Victoria from travellers recently returned from Bali. Disease onset for these 10 cases ranged between 10 August 2010 and 1 January 2011.

In 2010, diagnoses of legionellosis were highest in May (11%; n = 34,) and August (n = 33) (Figure 68). L. pneumophila occurred most frequently in the autumn months, with 46 cases reported over the period March to May 2010 (Figure 69). Twenty-one cases of L. pneumophila were reported in May 2010, the largest number of cases diagnosed in a month since 23 cases were reported in March 2006. L. longbeachae cases peaked in spring 2010, with 45 cases reported over the period September to November 2010, the majority (n = 21) of which occurred in November.

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Figure 69: Notified cases of legionellosis, Australia, 2005 to 2010, by month and year and organism

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Males accounted for 65% of legionellosis cases in 2010, with a male to female ratio of 1.9:1. There were no cases in people under the age of 15 years. The notification rate was highest in the 75–79 year age group (5.3). The highest age and sex-specific rates were observed in men aged 80–84 years (7.9) and women aged 75–79 years (4.4) (Figure 70).

Figure 70: Rate for legionellosis, Australia, 2010, by age group and sex

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Analysis of infecting species by age group showed that 89% (123/138) of L. longbeachae notifications were in persons aged 45 years or older, with the highest rate in the 75–79 year age group (2.4). Similarly, the proportion of L. pneumophila infections in persons 45 years or older was 87% (116/133), with the highest rate in the 70–74 year age group (2.5).

Mortality data were available for 58% of notifications. There were 7 reported deaths due to legionellosis in Australia in 2010, which was a decrease from 10 reported deaths in 2009. Those who died ranged in age between 55 and 86 years (median 76 years); 5 deaths were males and 2 deaths were females. There were 5 deaths associated with L. pneumophila infection and 2 deaths were associated with L. longbeachae (Table 17). Mortality data should be interpreted with caution given the large proportion of cases without outcome details and the variability across jurisdictions in reporting death to the NNDSS.

Leprosy

Leprosy is a chronic infection of the skin and peripheral nerves with the bacterium Mycobacterium leprae. Leprosy is a rare disease in Australia, with the majority of cases occurring amongst migrants from leprosy-endemic countries and occasional locally acquired cases in Indigenous communities. Trends in leprosy notifications in Indigenous and non-Indigenous Australians are shown in Figure 71.

Figure 71: Notified cases of leprosy, Australia, 1992 to 2010, by year and Indigenous status

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In 2010, 11 notified cases of leprosy were reported (8 male, 3 female), compared with 3 cases in 2009 and 11 in 2008. The majority of cases were reported from Victoria (n = 4) followed by Western Australia (n = 3) and Queensland (n = 2) with one each from New South Wales and the Northern Territory. Three cases were identified as Indigenous. Ten of the 11 cases were adults aged 24 years or older (range 24–55) and the remaining case was a 10-year-old.

Invasive meningococcal disease

Meningococcal disease is caused by the bacterium Neisseria meningiditis and becomes invasive when bacteria enter a normally sterile site, usually the blood (septicaemia), cerebrospinal fluid (meningitis) or both. The bacterium is carried by about 10% of the population without causing disease, and is transmitted via respiratory droplets. It occasionally causes a rapidly progressive serious illness, most commonly in previously healthy children and young adults. There are 13 known serogroups of meningococcus. Globally, serogroups A, B, C, W135 and Y most commonly cause disease.¹⁶ Historically, N. meningitidis serogroups B and C have been the major cause of invasive meningococcal disease (IMD) in Australia. There has been a marked decrease in rates of IMD due to N. meningitidis serogroup C infections following the introduction of the National Meningococcal C Vaccination Program in 2003.

In 2010, there were 230 notified cases of IMD; an 11% decrease from 259 cases in 2009, and the lowest number since 1996. Rates have halved from 2 to 1 case per 100,000 between 2004 and 2010. During 2010, case numbers started to rise in May and remained elevated over the winter months in a clear seasonal pattern before declining from a peak in October (Figure 72).

Figure 72: Notified cases of invasive meningococcal disease, Australia, 2005 to 2010, by month and year and serogroup

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Cases were evenly distributed amongst males and females in 2010 with 116 and 114 cases respectively. Ninety-four per cent of notified cases (n = 217) met the national case definition as ‘confirmed’ and the remaining 6% (n = 13) were classified as ‘probable’, based on clinical symptoms alone.

Ninety per cent of IMD cases in 2010 had serogroup data available of which 76% were caused by serogroup B organisms, 7% by C (Figure 72), 4% by W135 and 3% by Y (Table 18); a similar distribution to 2009.

Table 18: Notified cases of invasive meningococcal disease, Australia, 2010, by serogroup and state or territory

Serogroup	State or territory								Aust	% of total
	ACT	NSW	NT	Qld	SA	Tas	Vic	WA
B	1	50	2	41	22	5	34	19	174	76
C	0	6	0	5	2	0	1	1	15	7
W135	0	4	1	1	0	0	4	0	10	4
Y	0	3	0	0	1	0	3	1	8	3
Unknown	0	13	0	6	0	1	2	1	23	10

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Although there is no vaccine available to protect against serogroup B disease, the rate for IMD due to serogroup B organisms has continued to decline, particularly in the 0–4 and 5–9 year age groups over the period 2005 to 2010 (Figure 73). The highest age-specific IMD rate (6) in 2010 was in children aged 0–4 years. Of the cases reported in this age group, 80% were serogroup B. The highest rate for serogroup B infection in 2010 was 4.7 in the 0–4 year age group (n = 69), representing a 40% rate decline from 2005 (7.8, n = 101). There was a corresponding 50% decline in the 5–9 year age group from a rate of 1.6 (n = 22) in 2005 to 0.8 (n = 11) in 2010.

Figure 73: Rate for serogroup B invasive meningococcal disease, Australia, 2005 to 2010, by year and select age group

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Notification rates for IMD due to serogroup C infections remained low in most age groups in 2010. The largest decline has been in the 0–4 year age group, decreasing from a rate of 0.6 (n = 8) in 2005 to 0.1 (n = 2) in 2010 (Figure 74).

Figure 74: Rate for serogroup C invasive meningococcal disease, Australia, 2005 to 2010, by year and select age group

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In 2010, vaccination information was recorded for 3 of the 4 notified cases of serogroup C disease who were eligible for the meningococcal C vaccine (aged between 1 and 26 years in 2010) of which one was vaccinated and two were unvaccinated.

Mortality data for IMD were available for 50% of cases reported to the NNDSS in 2010. Of these, there were 14 deaths due to IMD (10 serogroup B, 1 serogroup C and 1 serogroup W135 and two of unknown serogroup) (Table 19). This was an increase from 10 deaths in 2009 (although mortality data completeness in NNDSS for 2009 was only 38%). Mortality data should be interpreted with caution given the low level of completeness and the variability across jurisdictions in reporting death as an outcome in NNDSS.

Table 19: Deaths due to invasive meningococcal infection, Australia, 2010, by serogroup and state or territory

Species	State or territory								Aust
	ACT	NSW	NT	Qld	SA	Tas	Vic	WA
Serogroup B	0	3	0	1	1	0	2	3	10
Serogroup C	0	0	0	0	0	0	0	1	1
Serogroup W135	0	1	0	0	0	0	0	0	1
Serogroup Y	0	0	0	0	0	0	0	0	0
Serogroup unknown	0	1	0	1	0	0	0	0	2
Total deaths	0	5	0	2	1	0	2	4	14

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Laboratory based meningococcal disease surveillance

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.

Tuberculosis

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 tuberculosis in the world, the disease remains a public health issue in the overseas-born and Indigenous communities. In 2010, 1,327 notified cases of TB were reported to NNDSS, a rate of 5.9 and consistent with the rate reported in 2009 (6) and 2008 (5.6). TB rates were higher than the national average in the Northern Territory (13), Victoria (7.8) and New South Wales (6.6), and the lowest rate occurred in Tasmania (2).

Further details and analysis of TB cases can be found in the tuberculosis annual report series which is published in CDI.