This article {extract} was published in Communicable Diseases Intelligence Vol 31 No 1 March 2007 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 2005 and classified as 'other bacterial infections' in NNDSS. A total of 1,826 notifications were included in this group in 2005, which accounted for 1.4% of all the notifications to NNDSS, a similar total and proportion as in 2004 (1,719 notifications and 1.6% 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 335 notifications of legionellosis reported in 2005, giving a national rate of 1.65 cases per 100,000 population. Of these, 264 cases (78.8%) were confirmed and 71 (21.2%) had a probable diagnosis.

In 2005, the highest rates of legionellosis were reported in South Australia (1.9 cases per 100,000 population, 58 cases) and Western Australia (1.7 cases per 100,000 population, 70 cases). Overall, the rate of notification was 1.65 cases per 100,000 population.

Legionellosis notifications showed a peak in autumn and spring, as in previous years (Figure 62). Rates of legionellosis have ranged between 0.8 and 2.6 cases per 100,000 population between 1999 and 2005; except in 2000, when rates reached 6.9 cases per 100,000 population as a result of the Melbourne aquarium outbreak with 125 cases.³⁴

Figure 62. Trends in notification rate of legionellosis, Australia, 2000 to 2005, by month of onset

In 2005, men accounted for 220 of the 335 notified cases of legionellosis resulting in a male to female ratio of 1.9:1. There were no cases in children aged under 15. Overall, the highest rate of infection was 5.6 cases per 100,000 population in the 70–74 year age group. The highest rate in men occurred in the over 85 year age group (9.8 cases per 100,000, n=10) and in women the highest rate was in the 75–79 year age group (3 cases per 100,000 population, n=21) (Figure 63).

Figure 63. Notification rate for legionellosis, Australia, 2005, by age group and sex

Data on the causative species were available for 315 of 335 (94%) legionellosis cases. Of these, 159 (50.5%) cases were identified as L. pneumophilia, 153 (48.6%) were L. longbeachae and 3 (1%) cases were L. micdadei or L. bozemanii (Table 15).

Table 15. Notifications of legionellosis, Australia, 2005, by species and state or territory

Species	State or territory
	ACT	NSW	NT	Qld	SA	Tas	Vic	WA	Aust
Legionella longbeachae	0	24	1	15	45	1	10	57	153
Legionella pneumophila	0	64	1	27	12	1	44	10	159
Other Legionella*	0	0	0	1	1	0	1	0	3
Unknown species	0	1	1	6	0	1	8	3	20
Total	0	89	3	49	58	3	63	70	335

* Legionella micdadei or Legionella bozemanii.

Data on the deaths in legionellosis cases was available for 195 (58.2%) notifications. There were 16 deaths due to legionellosis in Australia in 2005, giving a case fatality rate of 4.8%. The break down of deaths by jurisdiction and infecting Legionella species is shown in Table 16. The case fatality rate for infections with L. longbeachae infections (4.6%) was higher than for L. pneumophila (3.8%) though this difference did not reach statistical significance. Case fatality rates may be overestimated given the large proportion of cases without details of outcomes.

Table 16. Deaths due to legionellosis, Australia, 2005, by species and state or territory

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

An outbreak of 14 cases of Legionnaires’ disease was reported from southern Sydney, New South Wales. Of these, 12 were initially diagnosed by detection of urinary antigen and 2 by a fourfold rise in antibody titres to Legionella pneumophila serogroup 1. Nine people were hospitalised and there were no fatalities. A notable factor in this outbreak was the mild nature of the symptoms. The people affected were aged from 18 to 88 years, and 86% were male.

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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 2005, 10 leprosy cases were notified to NNDSS compared to 5 cases in 2004. There were 3 cases each in Western Australia, the Northern Territory and Queensland and 1 in New South Wales. Four cases occurred in men and 6 in women. Fifty per cent of cases were Indigenous Australians (2 in Western Australia and 3 in the Northern Territory). One case was reported to have been imported from overseas. The youngest case notified in 2005 was aged 19 years, and the oldest was aged 85 years.

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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.

Historically, in Australia, serogroups B and C have been the major cause of invasive meningococcal disease; however in 2005 serogroup B caused more disease than serogroup C as a result of the National Meningococcal C Vaccination Program, which commenced in January 2003.³⁵

In 2005, there were 393 notifications of invasive meningococcal disease in Australia, a decrease from 408 in 2004, and the lowest notifications since 1996. The national notification rate in 2005 was 1.9 cases per 100,000 population. The highest rate was reported from the Northern Territory (5.4 cases per 100,000, 11 cases).

Fifty-five per cent of cases (n=218) occurred in males, giving a male to female ratio of 1.2:1. As in previous years, the largest number of cases occurred in winter and spring (Figure 64). The majority of cases (n=352, 89.3%) were confirmed, and 42 (10.7%) had a probable diagnosis.

Figure 64. Trends in notification rate for meningococcal infections, Australia, 2002 to 2005, by month of onset

Of the 393 meningococcal notifications in 2005, 326 (82.7%) were serogrouped. Of these, 256 (78.5%) were serogroup B, 46 (14.1%) were serogroup C and 24 (7.4%) were infections with serogroup Y, serogroup W135 or serogroup A or serogroup 29–E (Table 17). In comparison, in 2004 81% (332/408) of notified cases were serogrouped; 240 (72.2%) were serogroup B and 74 (22%) were serogroup C.

Table 17. Notifications of meningococcal infection, Australia, 2005, by serogroup and state or territory

Species	State or territory
	ACT	NSW	NT	Qld	SA	Tas	Vic	WA	Aust
Serogroup B	4	72	6	43	18	10	62	41	256
Serogroup C	3	17	2	12	4	0	7	1	46
Other serogroups*	1	12	0	1	1	0	1	0	24
Unknown serogroup	0	39	3	6	3	0	13	3	67
Total	8	140	11	62	26	10	89	47	393

* Other includes serogroups A, 29-E, Y and W135.

The highest age specific meningococcal notification rate was in children aged 0–4 years with a rate of 10.4 cases per 100,000 population (131 cases). Seventy-seven per cent (101/131) of cases were serogroup B infection, which is the highest age-specific rate for serogroup B infection, with 8 cases per 100,000 population (Figure 65). In the 15–19 year age group, the overall rate of meningococcal infection was 3.9 cases per 100,000 population (54 cases), 42 (78%) of which were serogroup B. There were decreases in notification rates for the 25–29, 10–14 and 5–9 year age groups (Figure 65).

In the 25–29 year age group, there was a significant decrease in the number of serogroup B infections between 2004 and 2005 (OR=2.72, 1.51–4.92, p<0.001). There were 16 cases (1.2 cases per 100,000 population) in 2004, which was the highest reported number in the previous 5 years. In 2005, there were 6 notified cases (rate of 0.4 cases per 100,000 population), which is comparable to the number of notifications in 2003 (7 cases, 0.5 cases per 100,000 population). Decreases in the age-specific rates in the 10–14 and 5–9 years age groups were not significant (Figure 65).

Figure 65. Notification rate for meningococcal B infections, Australia, 2001 to 2005, by age group

There was a marked decrease in meningococcal C infection rates during 2003, the year the National Meningococcal C Vaccination Program was introduced. In 2005, the decrease in rates of serogroup C infection was greatest in the 15–19 year age group (Figure 66). In 2002, the serogroup C infection rate in this age group was 4.6 cases per 100,000 population (63 cases). Since then the rate in this age group has decreased steadily to 0.2 cases per 100,000 population (3 cases) in 2005. There was a significant decrease in the number of infections between 2004 and 2005 (OR=5.35, 1.48–23.06, p<0.005).

There were decreases in rates of serogroup C infections in all age groups except 0–4 years. The rate in the 20–24 year age group fell from 0.8 cases per 100,000 population (11 cases) in 2004 to 0.3 cases per 100,000 (5 cases) in 2005. In the 0–4 year age group, 8 cases (0.3 cases per 100,000 population) of meningococcal C infection were reported compared to 4 cases in 2004 (0.6 cases per 100,000 population). This is the first increase in the notification rate since 2001 (Figure 66).

Figure 66. Notification rate for meningococcal C infections, Australia, 2000 to 2005, by age group

The proportion of notified meningococcal samples that were not typed has decreased in recent years in all age groups. The proportion of untypeable samples in each age group is similar.

Data on death outcomes of meningococcal cases were available for 195 (49.5%) cases of meningococcal infection. There were 21 deaths recorded in 2005 giving a crude case fatality rate of 10.8%. The breakdown of deaths by jurisdiction and serogroup are shown in Table 18. The case fatality rate for group C meningococcal infections was 8.7%. For meningococcal group B infections it was 5.1%.

Table 18. Deaths due to meningococcal infection, Australia, 2005, by serogroup and state or territory

Species	State or territory
	ACT	NSW	NT	Qld	SA	Tas	Vic	WA	Aust
Serogroup B	0	4	0	1	1	0	4	3	13
Serogroup C	0	2	0	2	0	0	0	0	4
Other serogroups*	0	2	0	0	0	0	1	0	3
Unknown serogroup	0	0	0	0	0	0	1	0	1
Total	0	8	0	3	1	0	6	3	21

* Other includes serogroups A, Y and W135. (2 deaths were W135 infections, 1 was Y).

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Laboratory-based meningococcal surveillance

The Australian Meningococcal Surveillance Programme was established in 1994 to monitor and analyse 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 2005 have recently been published.³⁶

In 2005, a total of 345 isolates of N. meningitidis were analysed by the program. Consistent with routine surveillance data, serogroup B continued to be the predominant strain (251 isolates, 72.8%) nationally, followed by serogroup C (50 isolates, 14.5%). Serogroup B strains predominated in all jurisdictions.

The pattern of age distribution for meningococcal infection varied by phenotype. The highest proportion of serogroup B infections, occurred in the 0–4 year age group (99 cases, 90%). The largest proportions of serogroup C occurred in the 20–24 year (62%), and over 25 years (27%) age groups. This represents a shift in the age distribution of serogroup C infections, which have previously been reported most frequently in the 15–19 year age group.

In 2005, 206 of the 345 (59.7%) isolates were tested for susceptibility to the penicillin group of antibiotics. While 65 (31.5%) specimens were fully sensitive to penicillin (MIC 0.03 mg/L or less), 140 (68%) were less sensitive (MIC 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 (TB)

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 in the world, the disease remains a public health problem in the overseas-born and Indigenous communities. In 2005, 1,087 TB notifications were received by NNDSS; a rate of 5.4 cases per 100,000 population. In 2004, there were 1,076 cases notified nationally. The notification rate of TB was higher than the national average in the Northern Territory (6.7 cases per 100, 000 population), while the lowest rate occurred in Tasmania (1.3 cases per 100, 000 population).

The highest incidence was reported in people born overseas (20.6 cases per 100,000 population) and Indigenous Australians (5.2 cases per 100,000 population). The rate in the non-Indigenous Australian-born population was 0.8 cases per 100,000 population.

Further details can be found in the report published in this journal, 'Tuberculosis notifications in Australia, 2005'.³⁷