A print friendly PDF version is available from this Communicable Diseases Intelligence issue's table of contents.

Other bacterial infections

Legionellosis

Legionellosis is an acute bacterial infection with two clinical manifestations: Legionnaire's disease associated with pneumonia and Pontiac fever, which is generally self-limiting. Legionellosis describes a group of diseases caused by various species of Legionella as well as the pneumonia of classical Legionnaire's disease caused by Legionella pneumophila.

L. pneumophila occurs in water sources with a wide range of temperatures, pH and dissolved oxygen contents. Despite chlorination, the bacteria proliferate in cooling towers and water systems depending on favourable temperatures, sediment accumulation, and commensal microflora. Inhalation of aerosols generated by air-conditioning, nebulisers, humidifiers and showerheads is the major mode of transmission. Age, chronic lung disease, immunosuppression and cigarette smoking have been identified as important risk factors for legionellosis.⁶⁷L. longbeachae has been recognised for some years as a frequent cause of Legionella pneumonia in Australia.^68,69L. longbeachae has been isolated from a large proportion of potting mixtures in Australia, suggesting this route of exposure may be important in the epidemiology of sporadic legionellosis in Australia.⁷⁰

Legionellosis is notifiable in all States and Territories of Australia, and includes notifications of infections caused by all Legionella species. There were 249 notifications of legionellosis in 1999 resulting in a notification rate of 1.3 per 100,000 population compared with 1.4/100,000 population in 1998. The rates were highest in South Australia (4.2 per 100,000 population), Western Australia (2.3 per 100,000 population) and the Northern Territory (2.1 per 100,000 population, Table 2). Men accounted for 63 per cent of reported cases giving a male to female ratio of 1.7:1. Cases were recorded in age groups from 15 to 85 with a peak in the 50-54 year age group. Persons aged more than 60 years made up 47 per cent of all cases (Figure 43).

Figure 43. Notification rate for legionellosis, Australia, 1999, by age and sex



Most cases of legionellosis were sporadic, though Victoria reported 2 small clusters, one associated with a private spa and the other with contaminated cooling towers³⁵ (Kirk, 2000). Increased reporting of legionellosis in recent years may reflect the easier diagnosis using the urinary antigen test.⁷¹ Data on the isolated species were available for 132 of the cases. Of these 113 (86%) were identified as L. longbeachae and 19 (14%) as L. pneumophila. L. Pneumophila isolates were only identified in Queensland (14) and South Australia (5). New South Wales only reported L. Longbeachae. Legionella species information was not available from other jurisdictions.

Top of page

Leprosy

Leprosy is a chronic infection of skin and peripheral nerves with the bacteria Mycobacterium leprae. Leprosy is a rare disease in Australia, with the majority of cases occurring among migrants to Australia from leprosy-endemic countries.

There were 6 cases of leprosy notified nationally in 1999 compared with only 3 cases in 1998. Three of the 1999 cases occurred in Western Australia with one each in New South Wales, Queensland and Victoria. Of the 6 cases, three were male and three were female. The age range was 15-39 years.

Invasive meningococcal disease

Neisseria meningitidis is the cause of outbreaks of meningitis worldwide accounting for at least 500,000 cases and 50,000 deaths per annum. A pandemic in the sub-Saharan African 'meningitis belt', which began in 1996, has resulted in at least 300,000 cases to date and many thousands of deaths. An on-going epidemic of meningococcal disease in New Zealand since 1990 peaked at 13.3 cases per 100,000 population in 1997 (Martin, 2001, Communicable Disease Control Conference, April 2001, Abstract 2).

In Australia, there were 568 notifications of meningococcal disease nationally in 1999; a rate of 3.0 per 100,000 population compared with 2.4 per 100,000 population in 1998. Of the total, 365 (64%) cases were culture-confirmed. Of these 212 (58%) were serogroup B, 143 (39%) were serogroup C, 5 (1.5%) were serogroup W135 and 5 (1.5%) were serogroup Y. A pattern of seasonal variation in meningococcal infection notifications continued, with the greatest number of cases occurring in late winter or early spring (Figure 44). The distribution of notifications by age shows the highest peak in children aged 0-4 years and an additional peak in the 15-24 year age group. Overall the male to female ratio was 1.3:1 (Figure 45).

Figure 44. Notifications of invasive meningococcal disease, Australia, 1991 to 1999, by month of onset



Figure 45. Notification rate for invasive meningococcal disease, Australia, 1999, by age and sex



The Australian Meningococcal Surveillance Programme report for 1999⁷² reported the phenotype and antibiotic susceptibility of Neisseria meningitidis from invasive cases of meningococcal disease. Of the 368 isolates, 90 per cent of the isolates were either serogroup B or C. Serogroup B predominated in all States and Territories. Serogroup C isolates increased in Victoria and phenotype C-2a:P1.2 was the most frequently isolated phenotype. This phenotype was isolated infrequently before 1999. Another new Australian serogroup C phenotype C:2aP1.4(7) was isolated in New South Wales and Victoria. About three-quarters of all isolates showed decreased susceptibility to penicillin and three had reduced susceptibility to rifampicin. Case fatality rates were 9.4 per cent of culture-positive cases, with a higher mortality noted among cases with serogroup C disease.

Enhanced surveillance for invasive meningococcal disease commenced in Queensland in 1999.⁷³ The Queensland model includes probable cases for the first time, defined as a petechial or purpuric rash, isolation of N. meningitidis from a throat swab or an epidemiological link to a confirmed case. Enhanced surveillance has demonstrated a need to promote the use of parenteral antibiotics by GPs on suspicion of meningococcal disease and a need to encourage more timely reporting of cases to health authorities.

Victoria reported a marked increase in invasive meningococcal disease in 1999, with a doubling in the notification rate in the 15-19 year age group. There was a large increase in the proportion of cases caused by serogroup C from 13 per cent in 1998 to 31 per cent in 1999.³⁵ Serogroup B remained the dominant serogroup in children aged 0-4 years in all jurisdictions.

Tuberculosis

There are three national surveillance systems through which tuberculosis (TB) notifications are handled. The NNDSS provides the timeliest information on national TB notifications, but consists mainly of demographic information. The National Mycobacterial Surveillance System (NMSS), a surveillance system dedicated to tuberculosis and atypical mycobacterial infections, produces an annual report on TB notifications⁷⁴ with detailed information on risk factors, diagnostic methods, drug therapy and relapse status. 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.⁷⁵

In 1999, 1,153 TB notifications were reported nationally and the reporting rate was 6.1 per 100,000 population. This is consistent with rates since 1994. The highest rate was in the Northern Territory (51.8/100,000); this was inflated by a large number of cases diagnosed in East Timorese refugees in Darwin in September 1999 (see 1999 TB report following). There was little difference in notification rates between males and females with males accounting for just over 50 per cent of notifications. Some increases in jurisdictions such as Victoria were due to cases detected among refugees in Australian 'Safe Havens' program during the Kosovo and East Timor crises. Data from Victoria showed that 98 per cent of TB notifications were in people born outside Australia and that 35 per cent of cases were born in South East Asia. The 1999 TB report indicates that there are very low rates of tuberculosis in the non-indigenous Australian born population and that this rate is continuing to decline.


This article was published in Communicable Diseases Intelligence Volume 25, No 4, November 2001.