This article {extract} was published in Communicable Diseases Intelligence Vol 30 No 1 March 2006 and may be downloaded as a full version PDF from the Table of contents page.

Results, continued

Other bacterial infections

Legionellosis, leprosy, meningococcal infection and tuberculosis were notifiable in all states and territories in 2004 and classified as 'other bacterial infections' in NNDSS. A total of 1,799 notifications were included in this group in 2004, which accounted for 1.6 per cent of all the notifications to NNDSS, a similar total and proportion as in 2003 (1,826 notifications and 1.7% of total).

Legionellosis

Case definition – Legionellosis Both confirmed cases and probable cases are notified. Confirmed case: Requires isolation of Legionella, OR the presence of Legionella urinary antigen OR seroconversion or a significant increase in antibody level or a fourfold or greater rise in titre to Legionella. AND fever or cough or pneumonia. Probable case: Single high titre antibody titre to Legionella, OR detection of Legionella by nucleic acid testing, OR detection of Legionella by direct fluorescence assay. AND Fever or cough or pneumonia.

Legionellosis includes notifications of infections caused by all Legionella species. There were 310 notifications of legionellosis reported in 2004, giving a national rate of 1.6 cases per 100,000 population. Two hundred and thirty-four (75%) cases were confirmed, and 74 (24%) had a probable diagnosis.

In 2004, the highest rates of legionellosis were reported in South Australia (2.9 cases per 100,000 population, 45 cases) and Western Australia (2.5 cases per 100,000 population, 50 cases). Legionellosis notifications showed a peak in autumn and spring (Figure 62).

Figure 62. Trends in notification rate of legionellosis, Australia, 1999 to 2004, by month of onset

Rates of legionellosis have ranged between 0.8 and 2.6 cases per 100,000 population between 1999 and 2004, except in 2000, when rates reached 6.9 cases per 100,000 population as a result of the Melbourne aquarium outbreak, with 125 cases.⁴³

In 2004, men accounted for 73.5 per cent of all cases of legionellosis resulting in a male to female ratio of 2.8:1. Cases occurred in all age groups except 5–14 years, with the highest rates in the 75–79 year age group for men (13.4 cases per 100,000 population) and the 75–84 year age groups for women (3.0 cases per 100,000 population) (Figure 63).

Figure 63. Notification rates of legionellosis, Australia, 2004, by age group and sex

Data on the causative species were available for 294 (95%) of the legionellosis cases. Of these, 149 (51%) cases were identified as L. pneumophilia, 141 (45%) were L. longbeachae and 4 cases (1%) were L. micdadei (Table 23).

Table 23. Notifications of legionellosis, Australia, 2004, by state or territory and species

Species	State or territory								Total
	ACT	NSW	NT	Qld	SA	Tas	Vic	WA
Legionella longbeachae	0	29	2	7	36	1	65	43	183
Legionella pneumophila	1	51	0	18	9	0	3	5	87
Legionella micdadei	0	1	0	0	0	0	23	0	24
Unknown species	0	1	0	6	0	0	7	2	16
Total	1	82	2	31	45	1	98	50	310

Data on the death of legionellosis cases was available in 112 (36%) notifications. There were 16 deaths due to legionellosis in Australia in 2004, giving a case fatality rate of 5 per cent. The break down of deaths by jurisdiction and infecting Legionella species is shown in Table 24. The case fatality rate for infections with L. longbeachae infections (5%) was higher than for L. pneumophila (4%) but this difference did not reach statistical significance.

Table 24. Deaths due to legionellosis, Australia, 2004, by state or territory and species

Species	State or territory								Total
	ACT	NSW	NT	Qld	SA	Tas	Vic	WA
Legionella longbeachae	0	2	0	0	1	0	2	2	7
Legionella pneumophila	0	2	0	0	1	0	2	1	6
Legionella micdadei	0	0	0	0	0	0	1	0	1
Unknown species	0	0	0	0	0	0	2	0	2
Total	0	4	0	0	2	0	7	3	16

There was an outbreak of Legionella pneumophila in New South Wales, involving 12 cases. In June, four cases of Legionella pneumophila serogroup 1 were discovered in Victoria, with links to a town in north-eastern Victoria where an outbreak of six cases occurred in 2000.

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Leprosy

Case definition – Leprosy Only confirmed cases are notified. Confirmed case: Requires demonstration of acid fast bacilli in split skin smears and biopsies prepared from ear lobe or other relevant sites or histopathological report from skin or nerve biopsy compatible with leprosy (Hansen's disease) examined by an anatomical pathologist or specialist microbiologist AND compatible nerve conduction studies or peripheral nerve enlargement or loss of neurological function not attributable to trauma or other disease process, or hypopigmented or reddish skin lesions with definite loss of sensation.

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 Indigenous communities and migrants to Australia from leprosy-endemic countries.

In 2004, five leprosy cases were notified. This is the same number of cases as were notified in 2003. Three cases in occurred in New South Wales and one case occurred in both the Northern Territory and Queensland. Four of the five cases were female, and two cases were Indigenous Australians (one male and one female). Cases ranged in age from 30–79 years. Four cases had multibacillary leprosy and one had paucibacillary leprosy. One case had evidence of Grade 2 disability at presentation, with visible deformity or damage to hands/feet and visual impairment.⁴⁴

The WHO has established the goal of eliminating leprosy by 2005, which is defined as a reduction in the prevalence of leprosy to less than 1 case per 10,000 population. By the end of 2001, 36 of the 37 countries and areas that make up the Western Pacific Region, including Australia, reached this target.⁴⁵

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Invasive meningococcal disease

Case definition – Invasive meningococcal disease Both confirmed cases and probable cases are notified. Confirmed case: Defined as isolation of Neisseria meningitidis from a normally sterile site. Alternatively, detection of meningococcus by nucleic acid testing, or Gram negative diplococci in Gram stain in specimens from a normally sterile site or from a suspicious skin lesion, OR high titre IgM or a significant rise in IgM or IgG titres to outer membrane protein antigens, OR positive polysaccharide antigen test in cerebrospinal fluid AND disease compatible with invasive meningococcal disease. Probable case: Defined as the absence of evidence for other causes of clinical symptoms AND EITHER clinically compatible disease including haemorrhagic rash OR clinically compatible disease and close contact with a confirmed case within the previous 60 days.

In Australia, serogroups B and C are the major cause of invasive meningococcal disease. In response to community concerns about increases in meningococcal disease in Australia, the Australian Government approved the National Meningococcal C Vaccination Program, which commenced in January 2003.⁴⁶

In 2004, there were 408 notifications of invasive meningococcal disease in Australia, 170 cases fewer than in 2003 and a decrease of 29 per cent. The total in 2004 was the lowest since 1996 and is below the historical range (the 5 year mean by minus two standard deviations.) The national notification rate in 2004 was 2.2 cases per 100,000 population. Three hundred and seventy-three cases (91%) were confirmed, and 35 (8%) had a probable diagnosis.

The highest rates were reported from the Northern Territory (6.0 cases per 100,000 population, 12 cases), Tasmania (3.7 cases per 100,000 population, 18 cases) and the Australian Capital Territory (3.4 cases per 100,000 population, 11 cases). There was a small excess of cases among males (male to female ratio 1.2:1). The largest number of cases occurred in winter and spring (Figure 64).

Figure 64. Trends in notification rates of meningococcal infection, Australia, 2002 to 2004, by month of notification

Of the 408 meningococcal notifications in 2004, 342 (84%) were serogrouped. Of these 248 (73%) were serogroup B, 75 (22%) were serogroup C, and 19 (6%) were infections with serogroup Y, serogroup W135 or serogroup A (Table 25). In 2003, of 465 serogrouped notifications, 289 (62%) were serogroup B, and 158 (34%) were serogroup C.

Table 25. Notifications of meningococcal infection Australia, 2004, by state or territory and serogroup

Species	State or territory								Total
	ACT	NSW	NT	Qld	SA	Tas	Vic	WA
Serogroup B	4	82	8	49	11	7	55	32	248
Serogroup C	7	24	1	19	1	5	12	6	75
Other serogroups*	0	8	1	4	0	1	4	1	19
Unknown serogroup	0	39	2	9	1	5	8	2	66
Total	11	153	12	81	13	18	79	41	408

* Other includes serogroups A, Y and W135.

Overall, the highest age specific rate was in children aged 0–4 years with a rate of 10.4 cases per 100,000 population. Of these cases, 99 (75%), were serogroup B infection. In the 15–19 year age group, the overall rate of meningococcal infection was 4.8 cases per 100,000 population, 56 per cent (37 cases) of which were serogroup C.

The highest age-specific rates for serogroup B infection have persisted in the 0–4 years age group since 2000. In 2004, the rate for this age group was 6.5 cases per 100,000 population, (82 cases), while in the 15–19 years age group, the rate was 2.7 cases per 100,000 infections (37 cases) (Figure 65).

Figure 65. Notification rates of meningococcal B infection, Australia, 2000 to 2004, by age group

Between 2002 and 2004, rates of meningococcal serogroup C infection decreased in all age groups. There was a marked decrease in infection rates during 2003, the year the National Meningococcal C Vaccination Program was introduced. General practitioner based vaccination of 1–5-year-olds was completed at the end of 2004 in all jurisdictions. School based vaccination programs, first targeting 15–19-year-olds, then 6–14-year-olds, were complete in all jurisdictions, except South Australia by December 2004.

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The decrease in rates of serogroup C infection was greatest in the 15–19 year age group. In 2002, the serogroup C infection rate in the 15–19 year age group, was 4.6 cases per 100,000 population (63 cases). The rate in this age group decreased to 1.1 cases per 100,000 population (15 cases) in 2004. In the 0–4 year age group, the rate decreased from 1.8 to 0.4 cases per 100,000 population from 2002 to 2004. There were similar declines in the 5–9 and 20–24 year age groups (Figure 66).

Figure 66. Notification rates of meningococcal C infection, Australia, 2000 to 2004, by age group

Data on deaths from meningococcal infection were available for 172 (42%) cases. There were 20 deaths due to meningococcal infection in 2004 giving a crude case fatality rate of 5 per cent. The breakdown of deaths by jurisdiction and serogroup are shown in Table 26. The case fatality rate of 5.4 per cent for infections with meningococcal group C was the same as that for meningococcal group B infections. In 2003, the case fatality rate for infections with meningococcal group C was more than three times higher than for meningococcal group B infections.⁴⁷

Table 26. Deaths due to meningococcal infection, Australia, 2004, by state or territory and serogroup

Species	State or territory								Total
	ACT	NSW	NT	Qld	SA	Tas	Vic	WA
Serogroup B	0	4	0	1	1	1	5	1	13
Serogroup C	0	1	0	1	0	1	1	0	4
Other serogroups*	0	0	0	1	0	0	0	1	2
Unknown serogroup	0	1	0	0	0	0	0	0	1
Total	0	6	0	3	1	2	6	2	20

* Other includes serogroups A, Y and W135.

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Laboratory based meningococcal surveillance

The Australian Meningococcal Surveillance Programme 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 the surveillance in 2004 have recently been published.⁴⁸

In 2004, a total of 361 isolates of N. meningitidis were analysed by the program, a 27 per cent decrease from the 494 isolates analysed in the previous year. Consistent with routine surveillance data, serogroup B continued to be the predominant strain for the disease (243 isolates, 67%) nationally, followed by serogroup C (71 isolates, 20%). Serogroup B strains predominated in all jurisdictions except the Australian Capital Territory where 8 of 11 isolates were serogroup C.

The pattern of age distribution for meningococcal infection varied by phenotype. Serogroup B was more frequently reported in the 5–9 year (90.5%) and 0–4 year (87.4%) age groups, while the largest proportions of serogroup C occurred in the 25–44 year (35.7%), and 20–24 year (31.4%) age groups. This represents a shift in the age distribution of both serogroups from 2003 when most infections with serogroup B occurred in the 0–4 year age group, and serogroup C infections were reported most frequently in the 15–19 year age group.

In 2004, 147 of the 238 isolates (62%) tested showed decreased susceptibility to the penicillin group of antibiotics (minimum inhibitory concentration 0.06–0.5 mg/L). All isolates tested were susceptible to third generation cephalosporins and the prophylactic antibiotics, ciprofloxacin and rifampicin.

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Tuberculosis

Case definition – Tuberculosis Only confirmed cases are notified. Confirmed case: Defined as of Mycobacterium tuberculosis complex by culture, OR detection of M. tuberculosis complex by nucleic acid testing except which it is likely to be due to previously treated or inactive disease OR clinical diagnosis of tuberculosis including clinical follow-up assessment to ensure a consistent clinical course.

While Australia has one of the lowest rates of tuberculosis (TB) in the world, the disease remains a public health problem in the overseas-born and Indigenous communities. In 2004, 1,076 TB notifications were received by NNDSS, a rate of 5.4 cases per 100,000 population. There was an 8 per cent increase in the number of notifications in 2004 compared to 2003. The notification rates of TB were higher than the national average in the Northern Territory (14 cases per 100,000 population), and the lowest rate occurred in Tasmania (2.3 cases per 100,000 population).

The highest incidence was reported in people born overseas (21.7 cases per 100,000 population) and Indigenous Australians (8.1 cases per 100,000 population). By contrast the rate in the non-Indigenous Australian-born population was 1.2 cases per 100,000 population. For more details see the tuberculosis 2004 annual report in this issue of Communicable Diseases Intelligence.⁴⁹