Results, continued

Other bacterial infections

Legionellosis, leprosy, meningococcal infection and tuberculosis were notifiable in all states and territories in 2007 and classified as 'other bacterial infections' in the NNDSS. A total of 1,762 notifications were included in this group in 2007, which accounted for 1.2% of all the notifications to NNDSS, a similar total and proportion as in 2006 (1,866 notifications and 1.3% of total).

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Legionellosis

Legionellosis includes notifications of infections caused by all Legionella species. There were 307 notifications of legionellosis diagnosed in 2007, giving a national rate of 1.5 cases per 100,000 population. This was a decrease from the 350 cases reported in 2006. State and territory notification rates ranged from 0.6 cases per 100,000 population in Tasmania to 3.8 cases per 100,000 population in Western Australia. Compared with 2006, notification rates in 2007 increased in the Australian Capital Territory (1.2 cases per 100,000 population; 293% increase), New South Wales (1.5 cases per 100,000 population; 33% increase) and Queensland (1.2 cases per 100,000 population, 27% increase). A decrease in notification rates for 2007 compared with 2006 was seen in South Australia (1.1 cases per 100,000 population; 74% decrease), Victoria (0.8 cases per 100,000 population; 40% decrease) and Western Australia (3.8 cases per 100,000 population; 13% decrease). There was a negligible change in the notification rates for the Northern Territory and Tasmania from 2006 to 2007 (1.4 and 0.6 cases per 100,000 population, respectively).

In 2007, the highest number of legionellosis cases was diagnosed in June (36 cases, 12%) of all legionellosis notifications received and December (38 cases, 12%). These peaks were slightly later compared with previous years in which the highest numbers of notifications have generally been observed in autumn and spring months (Figure 63). Notifications of legionellosis by month of diagnosis have ranged between 14 and 43 cases between 2002 and 2007.

Figure 63: Notifications of legionellosis, Australia, 2002 to 2007, by month of diagnosis

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In 2007, males accounted for 196 (64%) of the 307 notified cases of legionellosis. There was 1 case of legionellosis (identified as L. pneumophila) in a child under the age of 5 years. Overall, the highest age specific notification rate was in the 80–84 years age group, with 6.5 cases per 100,000 population. The highest age specific notification rate among males was for the 80–84 years age group (10.4 cases per 100,000 population, 18 cases) and in females for the 65–69 years age group (3.9 cases per 100,000 population, 16 cases) (Figure 64).

Figure 64: Notification rate for legionellosis, Australia, 2007, by age group and sex

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Data on the causative species were available for 277 (90%) of the 307 legionellosis cases. Of these, 141 (51%) cases were identified as L. pneumophila, 134 (48%) were L. longbeachae and 2 (1%) cases were L. micdadei (Table 19).

Table 19: Notifications of legionellosis, Australia, 2007, by species and state or territory

Species	State or territory								Aust
	ACT	NSW	NT	Qld	SA	Tas	Vic	WA
Legionella longbeachae	0	29	2	10	14	2	6	71	134
Legionella micdadei	0	1	0	0	0	0	1	0	2
Legionella pneumophila	0	73	1	28	3	1	34	1	141
Unknown species	4	2	0	14	0	0	1	9	30
Total	4	105	3	52	17	3	42	81	307

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Of the 141 L. pneumophila notifications, serogroup data were available for 75 cases (53%); 73 (97%) of those further typed were L. pneumophila serogroup 1.

There were significant differences in the geographic distribution of L. longbeachae and L. pneumophila, with L. longbeachae infections comprising the majority of legionellosis notifications from South Australia and Western Australia, while L. pneumophila were the most common infecting species in the eastern States (Queensland, New South Wales and Victoria).

Data on the death of legionellosis cases were available for 144 (47%) notifications. There were 5 reported deaths due to legionellosis in Australia in 2007, giving a case fatality rate of 3.5%. The age range for the deaths was between 58 and 89 years. The break down of deaths by jurisdiction and infecting Legionella species is shown in Table 20. There were 2 deaths associated with L. longbeachae infection (both in Western Australia), giving a case fatality rate of 1.5%. Three patients with L. pneumophila infections died (all from New South Wales), giving a case fatality rate of 2.1%. Case fatality rates may be inaccurate given the large proportion of cases without details of death outcomes.

Table 20: Deaths due to legionellosis by species, Australia, 2007, by state or territory

Species	State or territory								Aust
	ACT	NSW	NT	Qld	SA	Tas	Vic	WA
Legionella longbeachae	0	0	0	0	0	0	0	2	2
Legionella micdadei	0	0	0	0	0	0	0	0	0
Legionella pneumophila	0	3	0	0	0	0	0	0	3
Unknown species	0	0	0	0	0	0	0	0	0
Total deaths	0	3	0	0	0	0	0	2	5
Total cases	4	105	3	52	17	3	42	81	307
Number of cases with death status reported	0 (0%)	4  (4%)	3 (100%)	0 (0%)	11 (65%)	3 (100%)	42 (100%)	81 (100%)	144 (47%)

The number of deaths decreased in 2007, relative to 2006, when there were 9 deaths reported. In 2006, data of death outcomes was reported for 66% of cases, this may in part account for the decrease in reported deaths. The number of deaths associated with legionellosis fell or remained constant in all jurisdictions except New South Wales where there were three more deaths in 2007 than in 2006.

Two large outbreaks of L. pneumophila were reported in 2007. One was a cluster of 6 cases related to a contaminated cooling tower near Circular Quay in Sydney.⁷¹ A second was a cluster of 9 cases linked to a cooling tower in the western suburbs in Melbourne.⁷²

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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 among migrants to Australia from leprosy endemic countries and occasional cases from Indigenous communities. Trends in the number of leprosy notifications in Indigenous and non-Indigenous Australians and the overall rate are shown in Figure 65.

Figure 65: Notifications of leprosy, Australia, 1991 to 2007, by indigenous status

In 2007, 12 cases of leprosy were notified compared with 6 cases in 2006. There were 4 cases in New South Wales; 2 cases in each of South Australia, Victoria and Western Australia; and a single case in both Queensland and Tasmania. Two of the cases were in Indigenous Australians. The notification from Tasmania was detected in a recent arrival from Africa, who had spent the previous 4 years in Uganda.

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Invasive meningococcal disease

In 2007, there were 304 notifications of invasive meningococcal disease in Australia, a decrease from 317 in 2006. The total number of notifications in 2007 was the lowest since 1996. A decline or stabilisation in notifications was seen in all jurisdictions except New South Wales (112 cases, a 5% increase) and Queensland (75 cases, a 10% increase). The national notification rate in 2007 was 1.4 cases per 100,000 population. The highest rate of notification was reported from the Northern Territory (2.8 cases per 100,000 population; 6 cases).

In 2007, males accounted for 154 of the 304 notified cases of invasive meningococcal disease, giving a male to female ratio of 1:1. As observed in previous years, the largest number of cases, for serogroups B and C, were diagnosed in winter and spring (Figure 66). The majority of cases (285, 94%) were confirmed, through the isolation of Neisseria meningitidis, with an additional 19 cases (6%) notified by probable diagnosis, based on clinical symptoms only.

Figure 66: Trends in notification rates (annualised) of invasive meningococcal disease, Australia, 2002 to 2007, by serogroup and month of diagnosis

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Of the 285 confirmed invasive meningococcal disease notifications in 2007, 255 (89%) were further typed. Of these, 213 (84%) were serogroup B, 20 (8%) were serogroup C and 22 (9%) were infections with serogroup W (9), serogroup X (1) and serogroup Y (12) (Table 21). In comparison, in 2006, 84% (265/317) of notified cases were serogrouped. Of these serogrouped notified cases 221 (83%) were serogroup B and 46 (15%) were serogroup C. Historically in Australia, serogroups B and C have been the major cause of invasive meningococcal disease.

Table 21: Notifications of invasive meningococcal disease, Australia, 2007, by serogroup and state or territory

Species	State or territory								Aust
	ACT	NSW	NT	Qld	SA	Tas	Vic	WA
Serogroup B	3	77	4	59	0	3	48	19	213
Serogroup C	0	10	2	6	0	0	2	0	20
Other serogroups*	0	7	0	6	0	2	7	0	22
Unknown serogroup	0	18	0	4	15	0	11	1	49
Total	3	112	6	75	15	5	68	20	304

* Serogroup W (9), serogroup X (1) and serogroup Y (12).

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Serogroup C infections were largely confined to Victoria, New South Wales and Queensland in 2007, similar to recent previous years when it has also been more predominant in the eastern states.

The highest age specific invasive meningococcal disease notification rate in 2007 was in children aged 0–4 years with a rate of 8.1 cases per 100,000 population (108 cases). Of the cases reported in this age group, 74% (80/108) were due to serogroup B infections, which represents the highest age specific rate for serogroup B infection across all age groups, at a rate of 6.0 cases per 100,000 population. Figure 67 shows the decline in rates of serogroup B infections in most age groups over the period from 2002 to 2007, the greatest of which is in the 0–4 years age group, from 8.9 cases per 100,000 population in 2002.

Figure 67: Notification rate for serogroup B invasive meningococcal disease, Australia, 2002 to 2007, by age group

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There has been a marked decrease in notification rates for invasive meningococcal disease caused by serogroup C since 2003, when the National Meningococcal C Vaccination Program was introduced (Figure 68). Under the program, all children turning 12 months of age have been eligible to receive free meningococcal C vaccine since 2003. The program also provided free meningococcal C vaccine for all children and adolescents who were aged 1–19 years in 2003 until 30 June 2006.¹³ The greatest decline in the rate of serogroup C disease since the introduction of the program is in the 15–19 years age group, from 4.9 cases per 100,000 population in 2002 (67 cases) to 0.1 cases per 100,000 population in 2007 (2 cases). The rates in the 20–24 years age group fell also from 2.5 cases per 100,000 population (33 cases) to 0.2 cases per 100,000 population (3 cases) over the same period. Rates in the 0–4 years age group fell from 2 cases per 100,000 population in 2002 (26 cases) to 0.3 cases per 100,000 population (4 cases) in 2007.

Figure 68: Notification rate for serogroup C invasive meningococcal disease infection, Australia, 2002 to 2007, by age group

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Death data for meningococcal cases were available for 123 (40%) notifications. There were 9 deaths due to meningococcal disease in 2007, corresponding to a case fatality rate of 30%. The break down of deaths by state or territory and serogroup is shown in Table 22. There were 5 deaths due to serogroup B (case fatality rate of 2.3%) and 3 deaths due to serogroup C disease (case fatality rate of 15.0%). Overall there was a decrease in deaths of meningococcal cases from 12 deaths in 2006 (death data was provided for 45% of cases in 2006).

Table 22: Deaths due to meningococcal infection, Australia, 2007, by serogroup and state or territory

Species	State or territory								Aust
	ACT	NSW	NT	Qld	SA	Tas	Vic	WA
Serogroup B	0	0	0	4	0	0	1	0	5
Serogroup C	0	3	0	0	0	0	0	0	3
Serogroup W135	0	0	0	0	0	0	0	0	0
Serogroup unknown	0	1	0	0	0	0	0	0	1
Total deaths	0	4	0	4	0	0	1	0	9
Total cases	3	112	6	75	15	5	68	20	304
Number of cases with death status reported	0 (0%)	4 (4%)	6 (100%)	5 (7%)	15 (100%)	5 (100%)	68 (100%)	20 (100%)	123 (40%)

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Laboratory based meningococcal surveillance

The Australian Meningococcal Surveillance Programme (AMSP) was established in 1994 for the purpose of monitoring and analysing isolates of Neisseria meningitidis from cases of invasive meningococcal disease in Australia. The program is undertaken by a network of reference laboratories in each state and territory, using agreed standard 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 2007 have recently been published.⁷³

In 2007, a total of 242 laboratory confirmed cases of invasive meningococcal disease were reported by the AMSP. Consistent with the NNDSS data, the AMSP reported that 85% (192 cases) were identified as serogroup B and 6.2% (14 cases) were serogroup C. No evidence of meningococcal capsular 'switching' was detected. About two-thirds of all isolates showed decreased susceptibility to penicillin (MIC 0.06–0.5 mg/L). All isolates remained susceptible to rifampicin. One serogroup B isolate had decreased susceptibility to ciprofloxacin.

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Tuberculosis

While Australia has one of the lowest rates of tuberculosis (TB) in the world, the disease remains a public health problem in those born overseas and for Indigenous Australians. In 2007, 1,139 TB notifications were received by NNDSS, a rate of 5.4 cases per 100,000 population. In 2006, there were 1,193 cases notified nationally, a rate of 5.8 cases per 100,000 population. The notification rate for TB was higher than the national average in the Northern Territory (24.7 cases per 100,000 population; 53 cases), while the lowest rate occurred in Tasmania (1.2 cases per 100,000 population; 6 cases).

Further details and analysis of TB notifications in 2007 can be found in the TB annual report to be published in the next edition of CDI.