Results, cont'd

Other bacterial infections

Legionellosis, leprosy, meningococcal infection and tuberculosis were notifiable in all states and territories in 2009 and classified as ‘other bacterial infections’ in the NNDSS. A total of 1,919 notifications were included in this group in 2009, which accounted for less than 1% of all the notifications to NNDSS, an increase in cases and a similar proportion as in 2008 (1,771 notifications 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.⁹⁰ There were 302 notifications of legionellosis reported in 2009, giving a national rate of 1.4 notifications per 100,000 population. This was an 11% increase from the 272 notifications reported in 2008 (1.3 notifications per 100,000 population). State and territory notification rates ranged from 0.9 notifications per 100,000 population in Victoria to 2.7 notifications per 100,000 population in South Australia, with no cases reported in Tasmania in 2009.

Data on the causative species were available for 94% (285) of cases: 57% (171) were L. longbeachae, 37% (112) were identified as L. pneumophila and 1 (1%) case each of L. micdadei and L. bozemanii were reported (Table 18).

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, in 2009 L. longbeachae was also notified more frequently than L. pneumophila in the eastern States of Queensland and New South Wales.

In 2009, diagnoses of legionellosis were highest in April (35 notifications, 12%) and May (34 notifications, 11%) (Figure 74). L. pneumophila occurred most frequently in the autumn months, with 45 cases reported over the period March to May 2009 (Figure 75). Twenty cases of L. pneumophila were reported in April 2009, the largest number of cases diagnosed in a month since 23 cases were reported in March 2006. L. longbeachae cases peaked in winter 2009, with 55 cases reported over the period June to August 2009, including 22 cases in July.

Figure 74: Notifications of legionellosis, Australia, 2005 to 2009, by state or territory and month and year of diagnosis

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Figure 75: Notifications of legionellosis, Australia, 2005 to 2009, by infecting species, and month and year of diagnosis

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Males accounted for 61% (184) of legionellosis notifications in 2009, with a male to female ratio of 1.6:1. There were no notifications in people under the age of 16 years. The notification rate was highest in the 75–79 years age group (6 per 100,000 population, 33 notifications). The highest age and sex-specific rates were observed in men aged 75–79 years (9.5 per 100,000, 24 notifications) and women aged 70–74 years (4.5 per 100,000 population, 16 cases, Figure 76).

Figure 76: Notification rates for legionellosis, Australia, 2009, by sex and age group

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An infecting species analysis by age group showed that 84% (144/171) of L. longbeachae notifications were in persons aged 45 years or older, with the highest rate in the 65–69 years age group (3.2 per 100,000 population, 28 notifications). The proportion of L. pneumophila infections in persons 45 years or older was also 84% (94/112), with the highest rate in the 70–74 years age group (2.6 per 100,000 population, 18 notifications).

Mortality data were available for 44% (133/302) of notifications. There were 10 reported deaths due to legionellosis in Australia in 2009, which was an increase from 5 reported deaths in 2008. Those who died ranged in age between 62 and 82 years (median 72 years); 7 deaths were in males and 3 deaths were in females. There were 6 deaths associated with L. pneumophila infection and 4 deaths associated with L. longbeachae (Table 18). 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.

Table 18: Notifications of legionellosis, Australia, 2009, by species and state or territory

	State or territory
Species	ACT	NSW	NT	Qld	SA	Tas	Vic	WA	Aust	Total %
Legionella pneumophila*	0	28	0	24	21	0	32	7	112	37.1
Legionella longbeachae†	0	64	3	28	23	0	10	43	171	56.6
Legionella micdadei	0	0	0	0	0	0	1	0	1	0.3
Legionella bozemanii	0	0	0	0	0	0	1	0	1	0.3
Unknown species	4	2	0	4	0	0	6	1	17	5.6
Total	4	94	3	56	44	0	50	51	302	100.0

* Four deaths.

† Six deaths.

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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 77.

Figure 77: Notifications of leprosy, Australia, 1992 to 2009, by Indigenous status and year of diagnosis

In 2009, 3 leprosy notifications (1 male and 2 females) were received, compared with 11 in 2008. There were 2 notifications in Queensland and one in Victoria. One notification was identified as an Indigenous Australian. The cases were aged 13, 21 and 28 years.

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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 the meningococcus. 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. 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 2009, there were 259 notifications of IMD, a 9% decrease from 285 cases in 2008, and the lowest number of notifications since 1996. Since 2004, notification rates have decreased from 2.0 cases per 100,000 population to 1.2 per 100,000 in 2009.

Males accounted for 54% (139) of IMD notifications in 2009, with a male to female ratio of 1.2:1. Notifications peaked in July. Ninety-six per cent of notified cases (248) met the national case definition as ‘confirmed’ and the remaining 4% (11) were classified as ‘probable’, based on clinical symptoms alone.

Eighty-six per cent of IMD notifications (224) in 2009 had serogroup data available of which 88% (1977) were caused by serogroup B organisms, 6% (14) serogroup C (Figure 78), 2% (5) serogroup W135, 4% (8) serogroup Y, and the remaining 16% were either unknown or untypeable (Table 19). In comparison, in 2008 of 285 notifications, 77% (220) were caused by serogroup B organisms, 7% (21) were serogroup C, 3% (8) serogroup W135, 2% (8) were serogroup Y, and 10% (28) were either unknown or untypeable.

Figure 78: Notifications of invasive meningococcal disease, Australia, 2004 to 2009, by serogroup and month and year of diagnosis

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Table 19: Notifications of invasive meningococcal disease, Australia, 2009 by serogroup and state or territory

	State or territory									Total (%)
Serogroup	ACT	NSW	NT	Qld	SA	Tas	Vic	WA	Aust
Serogroup B	2	58	5	50	0	3	35	24	197	76.1
Serogroup C	0	8	1	2	0	0	1	2	14	5.4
W135	0	5	0	0	0	0	0	0	5	1.9
Y	0	3	0	1	0	0	1	1	8	3.1
Unknown or untyped serogroup	0	22	0	7	22	0	5	1	35	13.5
Total	2	96	6	60	22	3	42	28	259	100.0

The highest age-specific IMD notification rate in 2009 was in children aged 0–4 years (6.4 per 100,000 population). Of the notifications reported in this age group, 81% were serogroup B. Although there is no vaccine available to protect against serogroup B disease, the rate for IMD due to serogroup B organisms has also declined in most age groups over the period 2004 to 2009 (Figure 79). The highest rate for serogroup B infection in 2009 was 5.2 per 100,000 population in the 0–4 years age group (74 notifications), representing a 36% decline from 2004 (103 notifications, 8.1 per 100,000). There was a corresponding 56% decline in the 5–9 years age group from 1.6 per 100,000 (21 notifications) in 2004 to 0.7 per 100,000 (9 notifications) in 2009.

Figure 79: Notification rate for serogroup B invasive meningococcal disease, Australia, 2004 to 2009, by select age group and year of diagnosis

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Notification rates for IMD due to serogroup C infections remained low in most age groups in 2009 (Figure 80). Since 2004, the largest decline has been in the 15–19 years age group, with 0.1 notifications per 100,000 population (1 notification) in 2009 compared with 1.2 per 100,000 (16 notifications) in 2004; a decline of 92%. Similarly, the rate in the 20–24 years age group fell from 0.9 per 100,000 (12 notifications) to 0.1 per 100,000 (1 notification) over the same period; a 89% decline.

Figure 80: Notification rate for serogroup C invasive meningococcal disease, Australia, 2004 to 2009, by select age group

Mortality data for IMD were available for 98 of the 259 (38%) notifications reported to the NNDSS in 2009. Of these, there were 10 deaths due to IMD (6 serogroup B, 1 serogroup C and 1 serogroup W135). This was an increase from 8 deaths in 2008 (mortality data were provided to the NNDSS for 51% of notifications in 2008). 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.

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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. The results of laboratory surveillance in 2009 have yet to be published.

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 problem in the overseas-born and Indigenous communities. In 2009, 1,335 TB notifications were received by NNDSS; a rate of 6.2 cases per 100,000 population. In 2008, there were 1,203 notifications (5.6 per 100,000). TB notification rates were higher than the national average in the Australian Capital Territory (6.5 per 100,000), New South Wales (6.9 per 100,000), the Northern Territory (12.5 per 100, 000) and Victoria (7.7 per 100,000. The lowest rate occurred in Tasmania (1.8 per 100,000).

Further details and analysis of TB notifications can be found in the tuberculosis annual report series to be published in CDI.