Results, continued

Other bacterial infections

Erratum: Figures 59 and 61 were incorrectly labelled as rates of disease. The Figures are actually notifications of disease. The Figures were corrected in March 2015.

Legionellosis, leprosy, meningococcal infection and tuberculosis were notifiable in all states and territories in 2002 and classified as 'other bacterial infections' in NNDSS. A total of 1,980 notifications were included in this group in 2002, which accounted for 1.9 per cent of all the notifications to NNDSS.

Legionellosis

Legionellosis includes notifications of infections caused by all Legionella species. There were 318 notifications of legionellosis reported in 2002 giving a national rate of 1.6 cases per 100,000 population. The annual trend since 1991 (Figure 59) shows a marked increase in notifications in 2000 because of the Melbourne aquarium outbreak.⁴² Between 1991 and 2000, there was a significant increase in the national legionellosis notification rate, even after excluding cases related to outbreaks.⁴² In 2002, the highest rates of legionellosis were reported in South Australia (4.3 cases per 100,000 population) and Western Australia (2.9 cases per 100,000 population). Legionellosis notifications showed a peak in reports in autumn and spring.

Figure 59. Trends in notifications of legionellosis, Australia, 1991 to 2002, by month of onset

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Men accounted for 205 of 318 (64%) cases of legionellosis resulting in a male to female ratio of 1.8:1. Cases occurred in almost all age groups, with the highest rates in the 75-79 year age group for men (9.9 cases per 100,000 population) and the 60-64 year age group for women (4.5 cases per 100,000 population) (Figure 60).

Figure 60. Notification rates of legionellosis, Australia, 2002, by age group and sex

Data on the causative species was available for 304 (96%) of the legionellosis cases. Of these, 118 (39%) cases were identified as Legionella pneumophilia. 151 (50%) were L. longbeachae and 36 (11%) were other species (L. micdadei or L. bozemannii, Table 13).

There were several outbreaks of legionellosis reported in 2002. Two outbreaks of L. pneumophila in Victoria, one involving eight cases and the other three cases, were associated with water cooling towers contaminated with L. pneumophila serogroup 1. No source was identified in another two outbreaks in Victoria in 2002. A cluster of L. longbeachae infection cases in New South Wales in July was attributed to use of potting mix. There was one death (Table 14). There were also two linked cases identified in Queensland, but no source of infection was identified

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Table 13. Notifications of legionellosis, 2002, by species and state or territory*

	ACT	NSW	NT	Qld	SA	Vic	WA	Total
* No reports from Tasmania. † Other includes species of Legionella micdadei and Legionella bozemannii.
Legionella longbeachae	1	20	1	16	60	17	36	151
Legionella pneumophila	0	21	0	26	6	58	7	118
Other species†	0	1	0	2	0	32	0	35
Unknown species	2	0	0	0	0	0	12	14
Total	3	42	1	44	66	107	55	318

In all there were 14 deaths identified as due to legionellosis in Australia in 2002, giving a case fatality rate of 4.3 per cent. The break down of deaths by jurisdiction and infecting Legionella species is shown in Table 14. The case fatality rate for infections with L. pneumophila (6/119, 5%) was not significantly higher than for L. longbeachae infections (7/154, 4.5%) in contrast to 2001, where the case fatality rate for L. pneumophila infections was significantly higher.¹⁴ All deaths reported to be caused by legionellosis occurred in older adults.

Table 14. Deaths due to legionellosis by species, 2002, by state or territory

	ACT	NSW	NT	Qld	SA	Vic	WA	Total
Legionella longbeachae	0	1	0	1	2	0	3	7
Legionella pneumophila	0	0	0	0	1	3	2	6
Other species*	0	0	0	0	0	0	1	1
Total	0	1	0	1	3	3	6	14

Leprosy

Leprosy is a chronic infection of the skin and peripheral nerves with the bacterium Mycobacterium leprae. Despite being eliminated in most countries, the disease remains as a major public health problem in six major endemic countries. Leprosy is a rare disease in Australia, with the majority of cases occurring among migrants to Australia from leprosy-endemic countries and in Indigenous communities.

In 2002, three leprosy cases were notified compared with five in 2001. The cases in 2002 occurred in Victoria, the Northern Territory and Western Australia. Two were male and one female and the age range was 25 to 34 years. Two cases were in Indigenous Australians (from the Northern Territory and the Kimberley region of Western Australia) and the third case was initially diagnosed in India.

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Invasive meningococcal disease

Meningococcal serogroups A, B, C, Y and W-135 are the major human pathogens. In Australia, serogroups B and C are the major cause of invasive meningococcal disease. Internationally, WHO estimated that there are at least 500,000 invasive meningococcal cases and 50,000 deaths every year.⁴³ In 2002 there were 684 notifications of invasive meningococcal disease in Australia, a small increase on the 677 reported in 2001. The national notification rate remained at 3.5 per 100,000 population. The highest rate was reported from Tasmania (5.5 per 100,000 population) as a result of an outbreak which began in September 2001 and continued into early 2002. The largest number of cases nationally occurred in winter (85 cases in July and 90 in August) (Figure 61).

Figure 61. Trends in notification rates of meningococcal infection, Australia, 1991 to 2002, by month of onset

The highest age specific rate was in children aged 0-4 years (13.6 cases per 100,000 population) and in the 15-19 year age group (10.3 cases per 100,000 population). There was a small excess of cases among males (male to female ratio 1.3:1), with the largest difference in rates between the sexes in the 15-19 year age group (male to female ratio 1.5:1) (Figure 62).

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Figure 62. Notification rates of meningococcal infection, Australia, 2002, by age group and sex

Among the 684 meningococcal cases, 563 (82%) were serogrouped. Of these, 299 (53%) were serogroup B, 222 (39%) were serogroup C, and 42 (7%) were serogroup W135 or serogroup Y (Table 15).

Table 15. Notifications of meningococcal infection by serogroups, 2002, by state or territory

	ACT	NSW	NT	Qld	SA	Tas.	Vic	WA	Total
* Other includes serogroups Y and W135.
Serogroup B	1	105	7	59	16	9	56	46	299
Serogroup C	4	54	1	46	8	17	87	5	222
Other serogroups*	0	5	0	11	1	0	10	15	42
Unknown serogroup	1	49	1	7	6	0	57	0	121
Total	6	213	9	123	31	26	210	66	684

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In 2002, there were 43 deaths due to meningococcal disease giving a crude case fatality rate of 6.2 per cent. The breakdown of deaths by jurisdiction and serogroup are shown in Table 16. The case fatality rate for infections with meningococcal group C (26/221, 11.7%) was significantly higher than for meningococcal group B infections (15/299, 5%, chi-square=7, p<0.01).

Table 16. Deaths due to meningococcal infection by serogroups, 2002, by state territory

	ACT	NSW	NT	Qld	SA	Tas.	Vic	WA	Total
* Other includes serogroup Y and W.
Serogroup B	0	8	0	2	3	0	2	0	15
Serogroup C	1	10	0	2	1	2	10	0	26
Other serogroups*	0	1	0	0	0	0	0	1	2
Unknown serogroup	0	0	0	0	0	0	0	0	0
Total	1	19	0	4	4	2	12	1	43

Laboratory based meningococcal surveillance

The Australian Meningococcal Surveillance Programme was established in 1994 for the purpose of monitoring and analyses of 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 the surveillance in 2002 have recently been published.⁴⁶

In 2002, a total of 393 isolates of N. meningitidis was analysed by the program, an increase from the 338 isolates analysed in the previous year. Serogroup B continues to be the predominant strain for the disease (210 isolates, 53%) nationally, followed by serogroup C (162 isolates, 41%). However, there was mix in the phenotypes circulating in the different states and territories. Serogroup C strains predominated in the Australian Capital Territory (80%), Tasmania (70%) and Victoria (56%).

The pattern of age distribution for meningococcal infection varied by the phenotype. Serogroup B was more frequently reported in the 0-4 year age group (40%). In contrast, serogroup C commonly occurred in the 15-19 year age group (29.6%).

In 2002, about two-thirds of all the isolates showed decreased susceptibility to the penicillin group of antibiotics (Minimum Inhibitory Concentration 0.06 to 0.5 mg/L). All isolates tested were susceptible to third generation cephalosporins and to the prophylactic antibiotics, rifampicin and ciprofloxacin.

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Tuberculosis

While Australia has one of the lowest rates of tuberculosis (TB) in the world. (Figure 63). The disease remains a public health problem in the overseas-born and Indigenous communities. In 2002, 975 TB notifications were received by NNDSS, a rate of 5.0 cases per 100,000 population a similar number and rate to 2001. The notification rates of TB were lower than the national average in the Australian Capital Territory, Queensland, South Australia, Tasmania and Western Australia as in previous years. The highest rate was reported in the Northern Territory (19.2 cases per 100,000 population).

Figure 63. Trends in tuberculosis notification rates, Australia, 1991 to 2002, by Indigenous status and country of birth

In 2002, the male to female ratio was 0.9:1. TB cases occurred in all age groups, with the highest age-specific rates reported in the 80-84 year age group (14.6 cases per 100,000 population). Detailed analyses of TB in Australia has recently been published.⁴⁶