This article {extract} was published in Communicable Diseases Intelligence Volume 23 Number 11 - 28 October 1999 and may be downloaded as a full version PDF from the Table of contents page.

Results continued

Other diseases

Legionellosis

Legionellosis is notifiable in all the States and Territories in Australia, and includes notifications of infections caused by all Legionella species. There were 271 cases of legionellosis reported to NNDSS in 1998 with a national annual rate of 1.4 per 100,000 population, an increase on 1997 (0.9 per 100,00). Both notifications and the rate were the highest in NNDSS since 1993. Large increases in notifications in 1998 compared with 1997 occurred in Queensland, South Australia and Victoria (Table 1).

A higher number of males were reported (72.7%) than females (27.3%) for legionellosis, with a male to female ratio of 2.7:1. The ages of cases ranged from 14 to 100 years, with 44% of reports for the 60+ age group (Figure 37).

The reported species were Legionella longbeachae (139, 51%), Legionella pneumophila (17, 6%) and 'another species' (6, 3%); 108 notifications (40%) were unspecified Legionella species as not all States and Territories reported these species separately. The peak of notifications was in October (Figure 38).

Figure 37. Notification rate of legionellosis, 1998, by age group and sex



Figure 38. Notifications of legionellosis, 1991-1998, by month of onset


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Leprosy

There were only three notifications of leprosy in 1998; from New South Wales, South Australia and Western Australia, significantly lower than 1997. The national rate was 0.02 per 100,000 population, compared with 0.1 per 100,000 in 1997. The reported cases were two males and one female.

Meningococcal infection

There were 455 notifications of meningococcal infection in 1998 (Table 1); a rate of 2.4 per 100,000 compared with 2.7 per 100,000 in 1997 (Table 2). The notifications included 140 serotype B (31%), 83 serotype C (18%), 6 serotype W (1%), 14 serotype Y (3%) and 208 (46%) unknown. A pattern of seasonal variation in meningococcal infection notifications continued, with the greatest number of cases occurring in late Winter/early Spring (Figure 39). The distribution of notifications by age shows the highest peak in the 0-4 years and additional peaks in the 15-24 years age groups and 75-85+ years (Figure 40). Overall, the male to female ratio was 1.2:1.

Figure 39. Notifications of meningococcal infection, 1992-1998, by month of onset



Figure 40. Notification rate of meningococcal infection, 1998, by age group and sex


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Tuberculosis

There are three national surveillance systems through which tuberculosis (TB) notifications are handled. The NNDSS provides the most timely information on national TB notifications, but demographic information is limited. The National Mycobacterial Surveillance System (NMSS), a surveillance system dedicated to tuberculosis and atypical mycobacterial notifications, produces an annual report on TB notifications¹¹ with detailed information on risk factors, diagnostic methods, drug therapy and relapse status. The 1997 annual report for the NMSS will be published in CDI in 1999. The Australian Mycobacterial Reference Laboratory Network (MRLN) maintains national data on drug susceptibility profiles, site of disease, age, sex and laboratory method of diagnosis for all mycobacterial isolates. These data are published annually in conjunction with the NMSS surveillance report.

In 1998, 982 notifications of TB were reported nationally, and the corresponding rate was 5.2 per 100,000. The highest disease rate of 14.2 per 100,000 was reported in the Northern Territory. These data are consistent with those reported since 1991.

Rates of TB were highest in males over the age of 65 years and females over the age of 75 years. A smaller peak in age-specific rates was reported in the 25-29 year age group (Figure 41).

There was little difference between notification rates between males and females with males accounting for just over 50% of the 976 notifications in which sex was reported.

Figure 41. Notification rate of tuberculosis, 1998, by age group and sex

Discussion

The peak of legionellosis in late 1998 was the highest since 1992. An outbreak occurred in Victoria at this time and cultures from cooling towers yielded Legionella pneumophila serogroup⁵¹ (CDNANZ personal communication).

Notification of the serogroup involved in meningococcal infection remains poor as almost half of the 1998 notifications of meningococcus are type unknown. Of the serogroup data provided, serogroup B was the most common being reported twice as frequently as serogroup C. This mirrors the Australian Meningococcal Surveillance Programme report for 1997 in which twice as many of referred isolates were type B (64%) as type C (32%).¹⁴ Not all notifications of meningococcal infection are linked to a referred isolate by the Australian Meningococcal Surveillance Programme. In 1997 there were 499 notifications and 343 (69%) had isolates typed by the surveillance program. Meningococcal notifications for 1998 were highlighted in surveillance reports in CDI^52,53 The Annual Report of the Australian Meningococcal Surveillance Programme for 1998 will be published in CDI later this year or early next year.

Tuberculosis rates in Australia have been stable over the last decade. Published surveillance reports, based on data collected by the NMSS have consistently identified elderly Australian born persons, migrants from high prevalence countries, and Indigenous Australians as those at increased risk of TB disease. Proposed changes to the national Tuberculosis information collection process will improve the information collected on the diagnosis of TB, further refine information on the risk factors for developing TB in Australia and allow information to be more readily linked between the NNDSS, NMSS and MRLN.