Results, cont

Campylobacter infections

Campylobacteriosis is not notifiable in New South Wales, including the Hunter Health Area, and data for 2004 were unavailable. With this exception, in 2004 OzFoodNet sites reported 15,640 cases of Campylobacter infection, which equated to a rate of 117 cases per 100,000 population.

This rate represented a 4.6 per cent increase over the mean rate for the previous six years and represents a sustained increase in notifications (Figure 4). Notifications peaked in November with 1,666 reports, which was the highest for a single month in the previous six years. Victoria and Tasmania reported marked increases in the number of cases of 29 per cent and 17 per cent respectively, while South Australia (-18%) and the Northern Territory (-6%) reported decreases (Figure 5). All other jurisdictions reported minimal change from historical totals.

Figure 4. Notifications and annual rates of Campylobacter infections, Australia excluding New South Wales, 1998 to 2004

Figure 5. Notification rates of Campylobacter infections for 2004 compared to mean rates for 1998–2003, Australia excluding New South Wales, by OzFoodNet site

The overall ratio of infections in males and females was 1.2:1. The highest age specific rates were in children in the 0–4 year age group, with male and female children in this age group having rates of 261 and 188 per 100,000 population respectively. In the Northern Territory, the rate of campylobacteriosis in Indigenous peoples was 186 per 100,000 population compared to only 69 per 100,000 population in non-Indigenous persons.

During 2004, there were nine investigations of Campylobacter outbreaks affecting a total of 104 people. This was considerably higher than for 2003, where only one outbreak was investigated.

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Listeria infections

OzFoodNet sites reported 66 cases of listeriosis in 2004, which represented a notification rate of 0.3 cases per 100,000 population (Figure 6). This was an increase of 6.5 per cent in the number of notifications compared to the historical mean. Western Australia and the Northern Territory both recorded 0.5 cases per 100,000 population. New South Wales recorded the greatest increase in notifications against historical averages with 30 notifications in 2004, which was 53 per cent higher than the six year mean. There was one small cluster of two cases in South Australia during 2004, although no source of infection was identified.

Figure 6. Notification rates of Listeria infections for 2004 compared to mean rates for 1998–2003, Australia, by OzFoodNet site

Eighty-nine per cent (59/66) of infections during 2004 were reported in persons who were either elderly and/or immunocompromised. Among cases of non-materno-foetal infections more males than females were notified, with the male to female ratio being 5.1:1. Sixty-one per cent (36/59) of cases were aged 65 years or greater. The highest age specific rate of 5.3 cases per 100,000 population was in males over the age of 65 years. Fourteen per cent (8/59) of non-pregnancy associated cases died.

There were seven materno-foetal infections with one foetal death recorded. This equates to a rate of 2.7 cases of Listeria infections per 100,000 births.¹⁵ A substantial decline in the number of materno-foetal infections occurred between 2000 and 2002, but numbers of infections rose again in 2003 and 2004 (Figure 7).

Figure 7. Notifications of Listeria showing non-pregnancy related infections and deaths and materno-foetal infections and deaths, Australia, 2000 to 2004

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Yersinia infections

The Communicable Diseases Network Australia agreed to stop reporting notifications of Yersinia infections to the National Notifiable Diseases Surveillance System, as of January 2001. The main reason for this was the apparent decline in incidence and lack of identified outbreaks. In May 2001, the Victorian Government revised regulations governing reporting of infectious diseases, at which time they removed yersiniosis from the list of reportable conditions. Yersinia is also not notifiable in New South Wales. No other Australian jurisdictions have amended their legislation to remove yersiniosis from lists of reportable conditions.

In 2004, OzFoodNet sites reported 108 cases of yersiniosis, which equated to a rate of 1.3 notifications per 100,000 population (Figure 8). The overall rate declined 6.4 per cent from previous years, when adjusted for the absence of reporting from Victoria and New South Wales. Queensland reported 93 per cent (100/108) of all cases, which equated to a rate of 2.6 cases per 100,000 population. The rates of yersiniosis in Queensland decreased in the 1990s, but have steadily increased since 2002. In 2004 in Queensland, the median age of yersiniosis cases was 29 years (range <1–87 years) and notifications were similar in all three Queensland health zones. Biotype for Yersinia enterocolitica cases in Queensland was known for 96 cases, of which 48 per cent (46/96) were biotype 4 serotype O:3 and 25 per cent were biotype 1A serotype O:5. South Australia reported six cases of yersiniosis, while the Australian Capital Territory and Western Australia reported one case each.

Figure 8. Notification rates of Yersinia infections for 2004 compared to mean rates for 1998–2003, Australia excluding Victoria and New South Wales, by OzFoodNet site

Shigella infections

OzFoodNet sites reported 520 cases of shigellosis during 2004, which equated to a notification rate of 2.6 cases per 100,000 population (Figure 9). This was a 29.1 per cent decrease in the notification rate compared with the six-year mean, after adjusting for the introduction of notifications from New South Wales in January 2001.

Figure 9. Notification rates of Shigella infections for 2004 compared to mean rates for 1998–2003, by OzFoodNet site

* Shigellosis became notifiable in New South Wales from 2001 onwards.

The highest rate of notification was in the Northern Territory (59 cases per 100,000 population), which was 20 times higher than the overall Australian rate. Within the Northern Territory, shigellosis was most commonly reported in the drier central regions and the rate in Alice Springs was 196 cases per 100,000 population. Eighty-one per cent (95/117) of notifications in the Northern Territory were in persons of Aboriginal or Torres Strait Island origin, which equated to a rate of 167 cases per 100,000 population. Only South Australia and Tasmania observed an increased rate compared to the six-year mean.

The male to female ratio of shigellosis cases was 0.8:1. The highest age specific rates were in males (11.6 cases per 100,000 population) and females (14.4 cases per 100,000 population) in the 0–4 year age group, with a secondary smaller peak in the 25–29 year age group for females. There were three reported outbreaks of shigellosis all of which were suspected to be spread from person-to-person. There were two outbreaks of Shigella flexneri 2a in the Northern Territory and one outbreak of Shigella sonnei biotype g in South Australia. In Australia, the majority of Shigella infections are thought to be due to person-to-person transmission, or are acquired overseas.

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Typhoid

OzFoodNet sites reported 74 cases of typhoid infection during 2001, equating to an overall notification rate of 0.4 cases per 100,000 population (Figure 10). The number of notifications was similar to previous years. The highest rate was reported in New South Wales (0.6 cases per 100,000 population). Tasmania, the Northern Territory and the Hunter sites did not report any cases during 2004.

Figure 10. Notification rates of typhoid infections for 2002 compared to mean rates for 1998–2001, by OzFoodNet site

Where travel status was known, sites reported that 81 per cent (55/68) of cases of typhoid had recently travelled overseas (Table 4). Forty-seven per cent (26/55) of these cases had travelled to the Indian subcontinent and the predominant phage types of S. Typhi were E1a (11 cases) and E9 (4 cases). Thirteen cases had recently travelled to Indonesia and the predominant phage types were E2 and E9 with two cases each. Five of the cases infected with typhoid reported recent travel to Samoa and the predominant phage type was E1a (3 cases).

One of the locally acquired cases infected with phage type E1 reported that their brother had visited from Samoa. Eight of the locally-acquired cases were considered to be chronic carriers. There was one case of typhoid in a laboratory worker. Travel status was unknown for six cases.

Table 4. Travel status and predominant phage types* for typhoid cases, Australia, 2004

Country	Number of cases	Predominant phage type (number of cases)
Albania	1	E9 (1)
Cambodia	4	E1a (2); E9 (1); Unknown (1)
China	1	O Variant (1)
El Salvador	1	A Degraded (1)
Indian Sub-continent	26	E1a (11); E9 (4); Degraded (3); O Variant (2); A degraded (1); Untypable (1); Unknown (4)
Indonesia	13	Untypable (3); E2 (2); E9 (2); E6 (1); D2 (1); Degraded (1); Unknown (3)
Jordan	1	Unknown (1)
Phillipines	2	Unknown (1); Degraded (1)
Samoa	5	E1a (3); E9 (1); E7 (1)
Sierra Leone	1	Unknown (1)
Locally acquired	13	E1a (5); E9 (2); Degraded (2); D2 (1); Untypable (1); Unknown (2)
Unknown	6	Unknown (5); Degraded (1)
Total	74

* Numbers in parentheses represent the number of cases infected by the phage type.

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Shiga toxin-producing Escherichia coli infections

OzFoodNet sites reported 46 cases of Shiga toxin-producing E. coli (STEC) infection during 2004 (Figure 11). This number does not include cases of haemolytic uraemic syndrome where a toxigenic E. coli was isolated. The notification rate of 0.2 cases per 100,000 population was a 0.5 per cent increase from the mean rate for the previous six years. South Australia (31 cases) reported the majority of cases, which represented a 3.1 per cent decrease over the historical mean for this State. The highest rate was in South Australia, which reported 2.0 notifications per 100,000 population (Table 5). The second highest number of cases was reported from Queensland, with 7 cases. There were no cases reported from Tasmania, the Hunter, the Australian Capital Territory or the Northern Territory during 2004.

Figure 11. Notification rates of Shiga toxin-producing Esherichia coli infections for 2004 compared to mean rates for 1998–2003, by OzFoodNet site

The male to female ratio of cases was 0.5:1 and the highest rates were in females aged between 5–9 years (0.8 cases per 100,000 population) and 20–24 years (0.7 cases per 100,000 population). The reason for the predominance of females amongst notified cases is unknown, but has been observed in previous years.

E. coli O157 was the most common serotype, accounting for 39 per cent of notifications. This serotype has been the most commonly reported for the last three years (Table 6). There were five cases of serotypes O111, four cases of serotype O26 and two cases of serotype O86. No serotype information was available for approximately one third of cases in South Australia due to the use of polymerase chain reaction (PCR) to diagnose infections.

The marked difference in notification rates between states and territories is a result of the practices that pathology laboratories use to screen faecal specimens for toxin-producing E. coli. South Australia has the most intensive testing regime and test bloody stool for the presence of the genes coding for production of Shiga toxin. This is reflected in the higher notifications rates reported in South Australia .

All of the cases appeared to be sporadic, except for two small clusters in South Australia and Queensland. South Australia reported a cluster investigation into two cases of STEC; one with E. coli O111 and one with E. coli O157. Both cases had visited a common native animal petting zoo, however, stool samples of native animals were negative for STEC. Queensland reported an investigation into a cluster of cases of E. coli O86:H27 in a single town in January [see the report by A. Morgan, et al in this issue, pp192–195]. There were four cases in total in two sets of siblings. Two children were diagnosed with haemolytic uraemic syndrome and are not included in this section. No source was identified for the Queensland cluster, although animal exposures were suspected as the cause.

Table 5. Infecting subtypes of Shiga toxin-producing Escherichia coli, Australia, 2004, by OzFoodNet site

State	Serotype						Unknown	Total
	O111	O141	O157	O26	O5	O86
NSW			1				2	3
Qld	1	1	1	1		2	1	7
SA	4		13*	2			12	31
Vic			2	1	1			4
WA			1					1
Total	5	1	18	4	1	2	14	46

* One case in South Australia was co-infected with Escherichia coli O113.

Table 6. Infecting subtypes of Shiga toxin-producing Escherichia coli, Australia, 2002 to 2004

Organism type	2004	2003	2002
O111	5	8	0
O113	1*	0	2
O157	17	13	20
O26	4	0	6
O141	1	0	0
O5	1	1	0
O86	2	0	0
O128	0	0	1
O130	0	1	0
O28	0	1	1
O2	0	0	1
Unspecified	15	27	26
Untypeable	0	2	2
Total	46	53	59

* One case was co-infected with Escherichia coli O157.

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Haemolytic uraemic syndrome

There were 17 cases of haemolytic uraemic syndrome reported during 2004, corresponding to an overall rate of 0.1 case per 100,000 population. New South Wales reported nine of these cases. Queensland reported three cases, South Australia two cases, while Victoria, Western Australia and the Northern Territory reported one case each (Figure 12). Cases occurred throughout the year and there was one investigation into a cluster of cases of E. coli O86 in Queensland, which involved two cases of haemolytic uraemic syndrome and two cases of Shiga toxin-producing E. coli [see pp192–195].

Figure 12. Numbers of notifications of haemolytic uraemic syndrome, Australia, 1998 to 2004, by month of notification

The male to female ratio was 0.4:1 and the highest rate of infection was in females in the 0–4 year age group (0.8 cases per 100,000 population). Details of specific toxigenic E. coli infections associated with haemolytic uraemic syndrome were not reported for 13 cases. Two cases were due to the O111 serotype and two were due to O86, while two cases had no STEC isolated.

 

This article was published in Communicable Diseases Intelligence Vol 29 No 2, June 2005.