Results, continued

Gastrointestinal diseases

Gastrointestinal diseases are a considerable burden on the community and the healthcare system in Australia. Foodborne pathogens alone are estimated to cause about 4.2 million cases of gastroenteritis per year.¹ Surveillance is vital in gathering information on pathogen specific gastrointestinal illnesses. Surveillance data however, highly underestimate the true incidence of pathogen specific gastrointestinal diseases Figure 1. For example, the probability of a patient with gastroenteritis in the community having a stool test, depends on whether a doctor is consulted or is available, whether the doctor orders a test, patient's age, the severity and duration of illness. Even when stools are collected from patients with gastroenteritis, about 60 per cent of samples have no pathogen identified.^2,3

In 2002, gastrointestinal diseases that were notified to NNDSS were: botulism, campylobacteriosis, cryptosporidiosis, haemolytic uraemic syndrome (HUS), hepatitis A, hepatitis E, listeriosis, salmonellosis, shigellosis, shiga-like toxin producing Escherichia coli/verotoxigenic E. coli (SLTEC/VTEC) infections and typhoid. Notification of gastrointestinal diseases increased marginally by 2 per cent, from 26,086 in 2001 to 26,708 in 2002. Compared with 2001, increases occurred in the number of notifications of cryptosporidiosis, salmonellosis and HUS. The increase in salmonellosis notifications may be due to improved surveillance and outbreak investigations conducted by OzFoodNet. Cryptosporidiosis became nationally notifiable in 2001, however 2002 was the first full-year of notifications of cryptosporidiosis from all jurisdictions. The number of notifications of HUS in 2002 was higher relative to 2001 notifications, when only three notifications were received, but was otherwise comparable to other years. There were no other changes of significance in the other notifiable gastrointestinal diseases Figure 4.

In this section reference will be made to OzFoodNet 2002 annual report of foodborne diseases.⁴ This report was used as a resource for additional information on foodborne disease outbreaks in Australia in 2002.

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Botulism

No cases of botulism were reported to NNDSS in 2002. While no classic foodborne botulism has been reported in Australia since the commencement of notifications in 1992, there have been five cases of infant botulism reported between 1998 and 2002.

Campylobacteriosis

There were 14,605 notifications of campylobacteriosis in Australia in 2002. All jurisdictions, except New South Wales, reported cases of campylobacteriosis. Campylobacteriosis is not notifiable in New South Wales. The national rate of notifications in 2002 was 112 cases per 100,000 population; a 10 per cent decrease compared with 125 cases per 100,000 population reported in 2001. South Australia had the highest notification rate (160.6 per 100,000 population) for the second consecutive year (Table 3), but this was 9 per cent lower than reports in this state in 2001.

Monthly notifications of campylobacteriosis in 2002, was consistent with previous years (1998 to 2002). with the number of notifications peaking in the third quarter of the year (Figure 15). In 2002, OzFoodNet reported only one campylobacteriosis outbreak, in Far North Queensland, which affected 24 persons and resulted in six hospitalisations.⁴

Figure 15. Trends in notifications of campylobacteriosis, Australia, 1998 to 2002, by month of onset

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The highest notification rate of campylobacteriosis was among children aged 0-4 years (Figure 16). In this age group notification rates were higher in males (283 cases per 100,000 population) than in females (205 cases per 100,000 population). The overall male to female ratio, as in previous years, was 1.2:1.

Figure 16. Notification rates of campylobacteriosis, Australia, 2002, by age group and sex

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Cryptosporidiosis

Cryptosporidiosis became nationally notifiable in 2001 and in 2002 NNDSS received the first full-year report from all jurisdictions. A total of 3,255 cases were reported to NNDSS, a notification rate of 16.6 cases per 100,000 population. Although Queensland reported 62 per cent (n=2,026) of all cryptosporidiosis notifications received by NNDSS, the Northern Territory had the highest notification rate, 109.6 cases per 100,000 population.

Children under the age of four had the highest notification rate of cryptosporidiosis (129 cases per 100,000 populations) (Figure 17). Notification rates of cryptosporidiosis decreased sharply at the age of 5 to 9 years for both males and females. Among those older than 10 years, females in the 30-34 year age group had the highest notification rate (20 cases per 100,000 population).

Figure 17. Notification rates of cryptosporidiosis, Australia, 2002, by age group and sex

Sixty-five per cent (n=2,112) of cryptosporidiosis notifications in 2002 occurred in the first quarter of the year, of which 77 per cent (n=1,635) were from Queensland (Figure 18). Public health authorities in Queensland noted an increase in cryptosporidiosis above historical levels. Infections through swimming pools, particularly pools hosting 'learn to swim classes', were identified as sources of exposure. Public health authorities issued health alerts where they recommended measures for avoiding infection and advised the swimming pool industry to ensure that persons with diarrhoea did not use public swimming pools.

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Figure 18. Notification of cryptosporidiosis, Australia (excluding Queensland) and Queensland, 2002, by month of onset

Hepatitis A

There were 388 cases of hepatitis A reported to NNDSS in 2002, a notification rate of two cases per 100,000 population. The number of notifications of hepatitis A has been steadily decreasing for the last decade, and compared to 2001, there was a decrease of 27 per cent in 2002 (Figure 19).

Figure 19. Trends in notifications of Hepatitis A, Australia, 1991 to 2002, by month of notification

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Compared to 2001, hepatitis A notification rates decreased in all jurisdictions except in the Northern Territory, where it increased by 21 per cent (from 19 to 23.7 cases per 100,000 population). The notification rate in the Northern Territory was 12 times the national average.

Males had a higher notification rate of hepatitis A (2.4 cases per 100,000 population) than females (1.5 cases per 100,000 population). The highest age specific rate of hepatitis A notifications among males was in the 20-24 year age group (4.5 cases per 100,000 population) and among females in the 35-39 year age group (2.7 cases per 100,000 population) (Figure 20).

Figure 20. Notification rates of hepatitis A, Australia, 2002, by age group and sex

Hepatitis A is commonly spread from person to person via close contact or from food or water that had been inadvertently contaminated by infected persons. The risk exposures among 214 cases of hepatitis A infection (55% of all notifications) showed that in 2002 the three frequently reported risk exposures identified were (in order of importance): overseas travel, homosexual contact, and household or close contact with confirmed cases (Table 6).

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Table 6. Risk exposures associated with infection with hepatitis A virus, Australia, 2002, by state or territory*

Exposure†	State or territory
	ACT	NSW	Qld	SA	Tas	Vic
Overseas travel	1	32	19	3	4	19
Homosexual contact	–	18	6	2	0	7
Childcare	–	3	3	0	0	13
Household/close contact of case	–	10	5	1	0	1
Injecting drug use	–	9	0	2	0	2
Sex worker	–	–	–	0	0	0
Other	–	189‡	–	0	–	0
Total with risk factors identified	1	92	68	7	4	42
Unknown	3	54	0	8	0	27
Total	4	146	68	15	4	74

* The Northern Territory and Western Australia did not report risk factors.

† Exposures are not mutually exclusive hence more than one exposure per person possible.

‡ Includes 19 cases who ate at a gathering and 51 regular restaurant/takeaway consumers.

-Data were not collected.

Hepatitis E

There were 12 cases of hepatitis E reported to NNDSS in 2002, two cases more than in 2001. Six cases were reported in New South Wales, two cases each in Tasmania and Victoria and a case each in the Australian Capital Territory and Queensland. There were nine males and three females, all aged between 20 and 54 years. Data on travel history were available for six cases and showed that all had travelled overseas.

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Listeriosis

In 2002, 59 cases of listeriosis were reported to NNDSS, a rate of 0.3 cases per 100,000 population. Listeriosis notifications have been stable at this rate since 1998. In 2002, 60 per cent of listeriosis cases were aged over 60 years, with the highest notification rate among males in the 80-84 year age group (Figure 21). There was a preponderance of infections in men (male to female ratio of 2.2:1) in contrast with 2001 when the male to female ratio was 0.7:1.

Figure 21. Notification rates of listeriosis, Australia, 2002, by age group and sex

In 2002, OzFoodNet reported 10 deaths among patients with non-pregnancy related listeriosis, which is equivalent to a 17 per cent case fatality rate. Two maternal-foetal Listeria infections were reported, resulting in one foetal death. In 2001, six cases of maternal-foetal listeriosis, including three foetal deaths, were reported. No common-source outbreaks of listeriosis were investigated by OzFoodNet in 2002.⁴

Salmonellosis (non-typhoidal)

A total of 7,756 salmonellosis cases were reported to NNDSS in 2002, a rate of 39.5 cases per 100,000 population and a 9 per cent increase from the rate reported in 2001 (36.2 cases per 100,000 population). During the five year period 1998-2001, the highest national notification rate was 40.6 cases per 100,000 population in 1998.

All jurisdictions reported cases of salmonellosis. The highest rates were in jurisdictions in the northern part of the country with the Northern Territory and Queensland reporting rates that were four times and two times the average national notification rate, respectively (Table 2). Notification rates of salmonellosis also varied by Statistical Division (Map 2), with the Kimberley in northern Western Australia having the highest notification rate of 320 cases per 100,000 population.

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Map 2. Notification rates of salmonellosis, Australia, 2002, by Statistical Division of residence

As in previous years, reports of salmonellosis peaked during summer (January to March). Thirty-six per cent of salmonellosis notifications in 2002 were notified during this period (Figure 22).

Figure 22. Trends in notifications of salmonellosis, Australia, 1998 to 2002, by month of onset

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Age specific notification rates of salmonellosis show a distribution consistent with previous years with children aged less than five years having the highest rate (210.6 cases per 100,000 population) (Figure 23).

Figure 23. Notification rates of salmonellosis, Australia, 2002, by age group and sex

The National Enteric Pathogens Surveillance Scheme reported serovars for 7,701 isolates;⁵ representing 99 per cent of notified cases of salmonellosis (n=7,756) in 2002. The 10 most frequently isolated serovars and phage types of Salmonella, which accounted for 43.2 per cent of all isolates, are shown in Table 7. Nationally, as in the previous year, the most commonly reported Salmonella serovar or phage type was Salmonella Typhimurium 135. Three Salmonella types: S. Typhimurium 170, S. Hvittingfoss, and S. Muenchen, were not among the top 10 serovars as in 2001 but were among the top 10 serovars reported in 2002. The distribution of Salmonella serovars varied across jurisdictions. The most commonly reported serovars in Queensland, Tasmania, and the Northern Territory were S. Virchow (10%), S. Mississippi (48%) and S. Ball (15%), respectively. S. Typhimurium was the most commonly reported serovar in the rest of the jurisdictions, accounting for 34 per cent of cases in the Australian Capital Territory, 28 per cent in New South Wales, 60 per cent in South Australia, 66 per cent in Victoria and 15 per cent in Western Australia.

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Table 7. Top ten Isolates of Salmonella, Australia, 2002

Organism	State or territory									Total %
	ACT	NSW	NT	Qld	SA	Tas	Vic	WA	Aust
S. Typhimurium 135	11	238	8	117	14	18	178	91	675	8.8
S. Typhimurium 9	16	268	0	77	24	12	151	44	592	7.7
S. Typhimurium 170	5	161	0	135	1	1	152	3	458	5.9
S. Saintpaul	0	37	20	225	11	2	44	44	383	5.0
S. Virchow 8	0	21	0	268	0	0	11	2	302	3.9
S. Birkenhead	0	95	3	134	4	0	8	1	245	3.2
S. Typhimurium 126	1	62	2	28	39	4	61	8	205	2.7
S. Chester	1	29	16	82	11	2	5	32	178	2.3
S. Hvittingfoss	1	17	6	110	3	1	13	2	153	2.0
S. Muenchen	0	20	12	55	9	3	9	24	132	1.7
Other	60	1,136	248	1,354	405	117	588	470	4,378	56.8
Total	95	2,084	315	2,585	521	160	1,220	721	7,701	100.0

Salmonellosis outbreaks

The most common cause of gastroenteritis outbreaks in Australia in 2002 was Salmonella, accounting for 28 per cent of gastroenteritis outbreaks investigated.⁴

S. Typhimurium alone accounted for 23 per cent of gastroenteritis outbreaks investigated by OzFoodNet in 2002, affecting 471 persons including 61 hospitalisations and two deaths. There were five significant outbreaks of salmonellosis in 2002, four of which occurred in South Australia (S. Typhimurium phage types 8, 99,135 and 126) and one in New South Wales (S. Montevideo).⁴

S. Typhimurium phage type 8 was identified as the agent for a disease outbreak that affected 78 persons including 15 hospitalisations in South Australia. The pathogen was isolated from several ingredients of a Caesar salad including; salad dressing, anchovies, and Parmesan cheese. The outbreaks of S. Typhimurium phage types 99, 135 and 126 affected between 20 and 50 persons each. An outbreak of S. Typhimurium phage type 99 was associated with the consumption of cakes sold in a bakery. Investigators found that the same piping bag was used to dispense sausage meat and cream for cakes. Outbreaks of S. Typhimurium phage type 135 and 126 were both associated with the consumption of Vietnamese rolls containing pork and/or beef.

In New South Wales, an outbreak of gastroenteritis associated with the consumption of food from a kebab shop affected at least 47 persons. Several sesame seed containing products in the shop, including tahini and hommus, were contaminated with S. Montevideo. Further investigation of unopened jars of the same products found contamination with S. Montevideo and S. Tennessee. These products were imported from Egypt and as a result of the investigation a nationwide consumer and trade recall of the imported products was initiated.

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Shigellosis

In 2002, 496 cases of shigellosis were reported to NNDSS, a notification rate of 2.5 cases per 100,000 population and a decrease of 13 per cent from the 2.9 cases per 100,000 population reported in 2001. The Northern Territory had the highest notification rate at 52 cases per 100,000 population. Although notification of shigellosis from New South Wales began in 2001, notifications of the disease continued to decline (Figure 24).

Figure 24. Trends in notifications of shigellosis, Australia, 1991 to 2002, by month of onset

Thirty-four per cent of notified cases of shigellosis were children under the age of four and this age group had the highest notification rate (14.1 cases per 100,000 population) (Figure 25). Despite the overall decrease in the number of notifications of shigellosis, there was an increase of 28 per cent in the 0-4 year age group compared to 2001. In the Northern Territory children under the age of four accounted for 64 per cent of shigellosis notifications in that jurisdiction.

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Figure 25. Notification rates of shigellosis, Australia, 2002, by age group and sex

Shiga-like toxin producing Escherichia coli/verotoxigenic E. coli

There were 51 cases of SLTEC/VTEC reported to NNDSS in 2002. With a notification rate of 0.3 cases per 100,000 population the rate of SLTEC/VTEC notifications remained stable relative to the previous year. Seventy-three per cent of cases were notified in South Australia (2.4 cases per 100,000 population), where bloody stools are routinely tested by polymerase chain reaction (PCR) for genes coding for shiga toxin. In South Australia, there was a 37 per cent increase in SLTEC/VTEC notifications compared with 2001. No cases were notified from the Australian Capital Territory, New South Wales, the Northern Territory or Tasmania. OzFoodNet reported that among typed E. coli, subtype O157 remains the main subtype (41% of total).

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Haemolytic uraemic syndrome

In 2002, 13 cases of HUS were reported to NNDSS, a rate of 0.1 cases per 100,000 population. No HUS cases were notified in the Australian Capital Territory, South Australia, Tasmania or Western Australia. Although there was a fourfold increase in HUS notifications compared to 2001, it was comparable with the three year mean (surveillance of HUS commenced in 1999; 3 year mean = 14). The lowest number of HUS notifications (n=3) since HUS surveillance commenced were received by NNDSS in 2001.

Among the 13 cases of HUS notified in 2002, six were males. The median age among males was 53 years (range 13-62 years) and among females the median age was 21 years (range 0-62 years). OzFoodNet reported that STEC was isolated in six cases of HUS of which three were E. coli O157, including one E. coli O157:H7.⁴

Typhoid

The notification rate of typhoid has been stable for the last five years. In 2002, there were 73 notifications of typhoid, a rate of 0.4 cases per 100,000 population. This represented a decrease by 14 per cent from the rate reported in 2001. The male to female ratio was 1:1 and the highest notification rates were in males aged 20-24 years (1.2 cases per 100,000 population) and in females aged 5-9 years (0.8 cases per 100,000 population) (Figure 26). The National Enteric Pathogen Surveillance Scheme identified 58 Salmonella Typhi isolates, 45 of which were from Australian residents and 13 from overseas visitors, including students. Of the 45 Australian residents, 36 had travelled to South and South-east Asian and African countries, but nine had no travel history recorded.

Figure 26. Notification rates of typhoid, Australia, 2002, by age group and sex