This article {extract} was published in Communicable Diseases Intelligence Vol 34 No 3 September 2010 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 2008 and classified as 'other bacterial infections' in the NNDSS. A total of 1,795 notifications were included in this group in 2008, which accounted for 1.1% of all the notifications to NNDSS, a similar total and proportion as in 2007 (1,799 notifications and 1.2% of total).
Legionellosis
Legionellosis includes notifications of infections caused by all Legionella species that meet the national surveillance case definition. There were 271 notifications of legionellosis reported in 2008, corresponding to a national rate of 1.3 notifications per 100,000 population. This was an 11% decrease from the 306 notifications reported in 2007 (1.5 per 100,000 population). State and territory notification rates ranged from 0.2 notifications per 100,000 population in Tasmania to 3.2 notifications per 100,000 population in Western Australia.
In 2008, the largest number of legionellosis notifications were diagnosed in May (31 notifications, 11%) and December (27 notifications, 10%) (Figure 70). As observed in previous years, the largest number of notifications of L. longbeachae in 2008 occurred in the spring months (Figure 71). In previous years L. pneumophila notifications have peaked in autumn and spring, however, in 2007 and 2008 these peaks have occurred slightly later, in late autumn and summer.75, 76
Figure 70: Notifications of legionellosis, Australia, 2004 to 2008, by month of diagnosis
Figure 71: Notifications of legionellosis, Australia, 2004 to 2008, by month of diagnosis and species
In 2008, males accounted for 184 (68%) of the 271 notifications of legionellosis resulting in a male to female ratio of 2.1:1. There were no notifications in people under the age of 19 years. Overall, the age group with the highest notification rate was the 75–79 year age group (4.9 per 100,000 population, 27 notifications). The highest age and sex specific rates were observed in men aged 70–74 years (7.5 per 100,000 population, 24 notifications) and women aged 75–79 years (3.4 per 100,000 population, 10 notifications) (Figure 72). An infecting species analysis by age group shows that 92% of L. longbeachae notifications were reported in persons 45 years or older and is most predominant in the 75–79 year age group with 19 notifications (3.5 per 100,000 population). The proportion of L. pneumophila infections in persons aged 45 years or older was 82% and is most predominant in the 70–74 year age group with 12 notifications (1.8 per 100,000 population).
Figure 72: Notification rates of legionellosis, Australia, 2008, by age group and sex
Data on the causative species were available for 260 (96%) of the legionellosis notifications: 158 (58%) were L. longbeachae, 97 (36%) were identified as L. pneumophila and 4 (1.5%) were L. micdadei or L. bozemanii. One notification was a co-infection of L. longbeachae and L. bozemanii (Table 17).
Table 17: Notifications of legionellosis, 2008, by species and state or territory
Species |
State or territory | Total (%) |
||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| ACT | NSW | NT | Qld | SA | Tas | Vic | WA | Aust | ||
| Legionella longbeachae* | 0 |
51 |
0 |
17 |
18 |
1 |
8 |
63 |
158 |
58.3 |
| Legionella pneumophila | 0 |
37 |
1 |
12 |
2 |
0 |
40 |
5 |
97 |
35.8 |
| Legionella micdadei† | 0 |
0 |
0 |
0 |
0 |
0 |
2 |
1 |
3 |
1.1 |
| Legionella bozemanii | 0 |
0 |
0 |
0 |
1 |
0 |
0 |
0 |
1 |
0.4 |
| Legionella longbeachae and bozemanii | 0 |
0 |
0 |
0 |
0 |
0 |
1 |
0 |
1 |
0.4 |
| Unknown species | 4 |
1 |
0 |
2 |
0 |
0 |
3 |
1 |
11 |
4.1 |
| Total | 4 |
89 |
1 |
31 |
21 |
1 |
54 |
70 |
271 |
100 |
* Four deaths.
† One death.
Of the 97 L. pneumophila notifications, 56 (58%) were serogroup 1, 2 (2%) were serogroup 2 and 34 (35%) were reported without serogroup data.
Historically, there have been differences in the geographic distribution of L. longbeachae and L. pneumophila, with L. longbeachae making up the majority of species in 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 2008 L. longbeachae notifications were more common in the eastern states of Queensland and New South Wales than notifications of L. pneumophila.
Seven notifications of L. pneumophila serogroup 1 infection with disease onset dates between 11 April and 10 May 2008 were associated with an outbreak at a suburban car wash in Victoria. A molecular analysis indicated a microbiological link between isolates recovered from 2 patient specimens and water samples from the car wash. A further 4 cases of L. pneumophila serogroup 1 notified during the period were residents of adjacent local government areas in Melbourne's southern suburbs although no definitive source for, or links between, these or any other cases notified in the 2nd quarter of 2008 were identified.77
Mortality data were available for 134 (49%) notifications. There were 5 reported deaths due to legionellosis in Australia in 2008, which was similar to 2007. The age range for the deaths was between 59 and 92 years (median age being 79 years); all deaths were in males. There were 4 deaths associated with L. longbeachae infection and 1 death was associated with L. micdadei (Table 17). Mortality data should be interpreted with caution given the large proportion of cases without details of death outcomes, and the variability across jurisdictions to report legionellosis to the NNDSS as the primary and secondary cause of death.
Leprosy
Leprosy is a chronic infection of the skin and peripheral nerves caused by the bacterium Mycobacterium leprae. Leprosy is a rare disease in Australia, with the majority of cases occurring amongst migrants to Australia from leprosy-endemic countries and occasional locally-acquired cases from Indigenous communities. Trends in the numbers of leprosy notifications in Indigenous and non-Indigenous Australians are shown in Figure 73.
Figure 73: Notifications of leprosy in Indigenous and non-Indigenous Australians, 1991 to 2008
In 2008, 11 leprosy notifications were received compared with 13 in 2007. There were 4 notifications in New South Wales, 2 notifications each in Queensland, Victoria and Western Australia and 1 notification in the Northern Territory. Eight notifications occurred in men and three in women. Three notifications were identified as Indigenous Australians. The age range of notified cases was 25–79 years (median 41 years).
Invasive meningococcal disease
Historically, in Australia, Neisseria meningitidis serogroups B and C have been the major cause of invasive meningococcal disease (IMD). There has been a marked decrease in rates for IMD due to N. meningitidis serogroup C infections following the introduction of the National Meningococcal C Vaccination Program by the Australian Government in 2003. In 2008, coverage of children aged 12 months immunised with meningococcal serogroup C vaccine reached 92.6% (data provided by the National Centre for Immunisation Research and Surveillance).
In 2008, there were 286 notifications of IMD, a 7% decrease from the 306 notifications in 2007, and the lowest number of notifications since 1996. Since 2003, the notification rates have decreased from 2.8 notifications per 100,000 populations to 1.3 notifications per 100,000 population in 2008.
In 2008, males accounted for 53% of IMD notifications (153 notifications), giving a male to female ratio of 1.1:1. The largest number of notifications was diagnosed in July (Figure 74). The majority of notifications (275 notifications, 96%) were laboratory confirmed, through the isolation of Neisseria meningitidis or detection of specific meningococcal DNA sequences through nucleic acid amplification. There were an additional 11 notifications (4%) reported as probable diagnosis, based on clinical symptoms only.
Figure 74: Trends in notification rates of invasive meningococcal disease, Australia, 2003 to 2008, by month of diagnosis and serogroups B and C
Of the 286 IMD notifications in 2008, 221 (77%) were caused by serogroup B organisms, 21 (7%) were serogroup C, 8 (3%) were serogroup W135, 7 (2%) were serogroup Y, and 29 (10%) were reported with an unknown serogroup (Table 18). Serogroup C infections were confined to the eastern seaboard states; New South Wales, Queensland and Victoria. In comparison, in 2007 of 306 notifications, 212 (69%) were serogroup B, 20 (7%) were serogroup C and 43 (14%) were reported with an unknown serogroup.
Table 18: Notifications of invasive meningococcal disease, Australia, 2008, by serogroup and state or territory
Serogroup |
State or territory | Total (%) |
||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| ACT | NSW | NT | Qld | SA | Tas | Vic | WA | Aust | ||
| Serogroup B | 2 |
50 |
4 |
72 |
19 |
1 |
50 |
23 |
221 |
77.3 |
| Serogroup C | 1 |
9 |
4 |
5 |
0 |
0 |
2 |
0 |
21 |
7.3 |
| Serogroup W135 | 0 |
5 |
0 |
2 |
1 |
0 |
0 |
0 |
8 |
2.8 |
| Serogroup Y | 0 |
3 |
0 |
1 |
0 |
0 |
3 |
0 |
7 |
2.4 |
| Unknown serogroup | 0 |
14 |
0 |
5 |
0 |
0 |
9 |
1 |
29 |
10.1 |
| Total | 3 |
81 |
8 |
85 |
20 |
1 |
64 |
24 |
286 |
100.0 |
The highest age specific IMD notification rate in 2008 was in children aged 0–4 years (7.2 notifications per 100,000 population). Of the notifications reported in this age group, 85% were serogroup B, this was also the age group with the highest age specific rate for serogroup B infection (6.1 notifications per 100,000 population).
Although there is no vaccine available to protect against serogroup B infections in Australia, the notification rates for IMD due to serogroup B infections has declined in most age groups over the period 2003 to 2008 (Figure 75). The highest notification rate for serogroup B infections was 6.1 notifications per 100,000 population in the 0–4 year age group (84 notifications) in 2008. This represents a 34% decline from the rate in 2003 (9.5 per 100,000 population, 121 notifications). The serogroup B notification rate in the 5–9 year age group saw a 54% decline in the notification rate from 1.3 per 100,000 population (18 notifications) in 2003 to 0.6 per 100,000 population (8 notifications) in 2008.
Figure 75: Notification rate for serogroup B invasive meningococcal disease, Australia, 2003 – 2008, by select age group
Notification rates for IMD due to serogroup C infections remained low in all age groups in 2008 (Figure 76). Since 2003, the largest decline has been in the 20–24 year age group with 0.1 notifications per 100,000 population (2 notifications) in 2008 compared with 2.3 notifications per 100,000 population (32 notifications) in 2003; an overall decline of 94.4%. The notification rate in the 15–19 year age group fell from 2.6 notifications per 100,000 population (36 notifications) to 0.2 notifications per 100,000 populations (3 notifications) over the same period; a 92.2% decline. Rates in the 0–4 year age group fell from 1.3 notifications per 100,000 population in 2003 (16 notifications) to 0.3 notifications per 100,000 population (4 notifications) in 2008.
Figure 76: Notification rate for serogroup C invasive meningococcal disease, Australia, 2003 to 2008, by select age group
Mortality data for IMD were available for 145 notifications (51%). Of these notifications, there were 7 deaths (6 serogroup B and 1 serogroup C) due to IMD in 2008. This was a decrease from 9 deaths in 2007 (mortality data were provided for 40% of notifications in 2007). Mortality data should be interpreted with caution given the large proportion of cases without details of death outcomes, and the variability across jurisdictions to report meningococcal to the NNDSS as the primary and secondary cause of death.
Laboratory based meningococcal disease surveillance
The Australian Meningococcal Surveillance Program (AMSP) was established in 1994 for the purpose of monitoring and analysing isolates of Neisseria meningitidis from cases of IMD 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 2008 have recently been published.78
In 2008, there were 260 laboratory confirmed cases of IMD. Consistent with the NNDSS data, the AMSP reported that 85% were identified as serogroup B (223 notifications) and 6.5% (17 notifications) were serogroup C. No evidence of meningococcal capsular 'switching' was detected. About three-quarters of all isolates showed decreased susceptibility to the penicillin group of antibiotics (MIC 0.06 to 0.5 mg/L). All isolates remained susceptible to ceftriaxone. One isolate had reduced susceptibility to rifampicin and two had reduced susceptibility to ciprofloxacin.
Tuberculosis
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 2008, 1,228 TB notifications were received by the NNDSS, corresponding to a rate of 5.7 notifications per 100,000 population. In 2007 there were 1,174 notifications (5.6 per 100,000 population). The notification rate of TB was higher than the national average in the Northern Territory (14.6 notifications per 100, 000 population), New South Wales (7.2 per 100,000 population), and Victoria (7.1 per 100,000 population. The lowest rate occurred in Tasmania (1.6 per 100,000 population).
Further details and analysis of TB notifications can be found in the tuberculosis annual report series to be published in CDI.
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Communicable Diseases Surveillance
This issue - Vol 34 No 3, September 2010
NNDSS Annual report 2008
Communicable Diseases Intelligence