Results, continued

Gastrointestinal diseases

In 2007, gastrointestinal diseases notified to NNDSS were: botulism, campylobacteriosis, cryptosporidiosis, haemolytic uraemic syndrome (HUS), hepatitis A, hepatitis E, listeriosis, salmonellosis, shigellosis, STEC infections and typhoid.

Notifications of gastrointestinal diseases in 2007 increased 9% to 30,325 from 27,947 in 2006 (Table 7).

Campylobacteriosis, salmonellosis and STEC exceeded the 5-year mean by more than 2 standard deviations, while typhoid, HUS and cryptosporidiosis were increased but did not exceed 2 standard deviations (Figure 3).

OzFoodNet, Australia's enhanced foodborne disease surveillance network monitors the incidence of diseases caused by pathogens commonly transmitted by food through population-based passive and enhanced surveillance for notifiable gastrointestinal diseases and for outbreaks of gastroenteritis and enteric diseases. In 2007, OzFoodNet aggregated and analysed data from NNDSS and enhanced surveillance data from OzFoodNet sites on the following 8 diseases or conditions, a proportion of which may be transmitted by food: non-typhoidal salmonellosis; campylobacteriosis infections (except in New South Wales); listeriosis; shigellosis; typhoid; STEC infections; botulism; and HUS. These data are reported in detail elsewhere.¹⁴

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Botulism

Foodborne botulism arises from the consumption of a food which is contaminated with pre-formed Clostridium botulinum toxin.

In 2007, there was 1 case of botulism, reported from Victoria. The Department of Human Services (DHS) was notified of a case of suspected botulism in a 25-year-old male. The notifying clinician gave a history of onset of dizziness, lethargy, blurred vision and respiratory distress followed by a rapid decline, which included respiratory failure requiring intubation and ventilation in an intensive care unit. A provisional diagnosis of stroke or multiple sclerosis was made but initial investigations were negative. The day following notification to DHS, the case became completely paralysed. A faecal enema specimen was forwarded to the University of Melbourne, Microbiological Diagnostic Unit for confirmation of the diagnosis. Clostridium botulinum toxin was detected in the faecal specimen, which was later identified as A2. An extensive investigation of a possible food source was conducted by DHS.¹⁴

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Campylobacteriosis

Campylobacteriosis is notifiable in all jurisdictions, except New South Wales.

In 2007, there were 16,984 notifications of campylobacteriosis, a 10.2% increase over the 15,407 notifications reported in 2006. The national rate of campylobacteriosis notifications in 2007 was 120.2 cases per 100,000 population, with the highest age and sex specific notification rates amongst males and females aged 0–4 years¹⁴ (Figure 14). Amongst children aged under 5 years, the highest notification rates were in boys aged 1 year (236.8 notifications per 100,000 population) (Figure 14, inset). Prevention measures should be targeted towards more regular cleaning of hands and dummies of young children, particularly when contact with animals and outdoor environments has taken place, as a recent study conducted by OzFoodNet has shown that these are risk factor for Campylobacter infection in children aged 0–4 years.¹⁵

Figure 14: Notification rate for campylobacteriosis, Australia, 2007, by age group and sex, and inset: age and sex in children aged under 5 years

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Cryptosporidiosis

In 2007, 2,810 notifications of cryptosporidiosis were reported to NNDSS representing a national rate of 13.4 cases per 100,000 population. This represents a 12% decrease over the number of notifications reported in 2006.

The highest rates of cryptosporidiosis were reported in the Northern Territory (51.6 cases per 100,000 population), Western Australia (28.9 cases per 100,000 population) and South Australia (28.3 cases per 100,000 population).

The majority of cryptosporidiosis cases in 2007 were in children aged under 10 years (52%). The highest age and sex specific notification rate was in boys aged 1 year, with 150.7 cases per 100,000 population (Figure 15).

Figure 15: Notification rate for cryptosporidiosis, Australia, 2007, by age group and sex, and inset: age and sex in children aged under 5 years

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Haemolytic uraemic syndrome

During 2007, there were 19 cases of haemolytic uraemic syndrome; a rate of 0.1 cases per 100,000 population, the same as the mean of 0.1 cases per 100,000 population between 2002 and 2006. The majority of these were reported from New South Wales (n=13). The median age of notifications was 6 years, with a range of 1–44 years. Similar to previous years, the highest notification rate was in children aged 0–4 years, with eight of the 19 notifications in this age group (0.6 notifications per 100,000 population).¹⁴

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Hepatitis A

The marked decline in notifications of hepatitis A in recent years is continuing (Figure 16).¹³ In 2007, there were 165 cases of hepatitis A, compared with a mean of 349 cases per year between 2002 and 2006. This decline is likely to be due to increased uptake of vaccine amongst high risk groups such as travellers, and targeted vaccination programs for Indigenous children.¹³ The proportion of cases who are known to be Indigenous is also decreasing. Between 2002 and 2006, an average of 11% of cases (39/349 cases per year) were Indigenous, while in 2007, no cases were known to have been Indigenous, with indigenous status known for 82% of cases (Table 11).

Figure 16: Trends in notifications of hepatitis A, Australia, 1991 to 2007, by month of diagnosis¹³

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Table 11: Hepatitis A notifications, Australia, 2002 to 2007, by indigenous status

Year	Indigenous		Non-Indigenous		Unknown
	n	%	n	%	n	%
2002	32	8	270	69	88	23
2003	52	12	322	75	56	13
2004	37	12	251	79	31	10
2005	48	15	232	71	46	14
2006	28	10	218	78	35	12
2007	0	0	136	82	29	18

In 2007, the majority of hepatitis A cases were acquired overseas (60%, 99/165), with Indonesia (16 cases) and India (14 cases) the most frequently reported place of acquisition for overseas acquired cases (Table 12).

Table 12: Notifications of hepatitis A, Australia, 2007, by state or territory

State	Number of cases	Number acquired overseas	Per cent overseas acquired
Australian Capital Territory	2	2	100
New South Wales	65	42	65
Northern Territory	5	4	80
Queensland	28	12	43
South Australia	5	4	80
Tasmania	3	0	0
Victoria	36	26	72
Western Australia	21	9	43
Total	165	99	60

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Hepatitis E

In 2007, there 18 notifications of hepatitis E, compared with 24 notifications in 2006 and an average of 21 cases per year between 2002 and 2006. One case was reported from the Australian Capital Territory, eight from New South Wales, three from Queensland and six from Victoria.

In 2007, 89% (16/18) of cases were known to have been acquired overseas, of which 22% (4/18) were female. The median age of cases was 30 years (range 18–57 years), reflecting high rates of overseas travel in younger adults.

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Listeriosis

In 2007, 50 cases of Listeria monocytogenes infection were reported to NNDSS, a crude rate of 0.2 per 100,000 population. The 2007 notification rate was similar to the 5-year historical mean (0.3 cases per 100,000 population). Seventy-six per cent (38/50) of notifications were in people aged 60 years or over. The highest age specific notification rate was in the 80–84 years age group, with a notification rate of 2.9 cases per 100,000 population. In 2007, 52% of cases were female. Four of the 50 cases were pregnancy-associated, occurring either in infants or pregnant women.¹⁴

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Salmonellosis (non-typhoidal)

In 2007, there were 9,484 cases of Salmonella infection, a rate of 45 cases per 100,000 population, which is a 15% increase over the mean of the previous 5 years. Notification rates ranged from 32 cases per 100,000 population in the Australian Capital Territory to 244 cases per 100,000 population in the Northern Territory. The highest age specific rate of Salmonella infection was in children in the 0–4 years age group (202 cases per 100,000 population),¹⁴ with 28% of all cases in this age group. Figure 17 shows that in this age group, the highest rates were in those aged under 1 year (384 per 100,000 population for males and 385 per 100,000 population for females).

Figure 17: Notification rate for Salmonella infection, Australia, 2007, by age and sex

In 2007, the most commonly notified Salmonella serotype was S. Typhimurium. The most commonly notified phage type was S. Typhimurium 135, with 722 notifications in 2007. S. Typhimurium 9 was the second most common phage type notified in Australia in 2007. Western Australia ceased routine phage typing of S. Typhimurium, S. Enteritidis and S. Virchow in July 2007.¹⁴

Risk factors for salmonellosis in children aged 0–4 years are currently under investigation through OzFoodNet. Most salmonellosis in Australia is transmitted through contaminated food.

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Shigellosis

In 2007, there were 597 cases of shigellosis reported to NNDSS compared with 543 in 2006. The 2007 notification rate was 2.8 cases per 100,000 population compared with a mean of 2.7 cases per 100,000 population between 2002 and 2006. As in previous years, the highest notification rate was in the Northern Territory, with 80.5 cases per 100,000 population.¹⁴

The highest age specific notification rates were amongst males and females in the 0–4 years age group, with age specific rates of 11.8 and 11.7 notifications per 100,000 population (Figure 18). In 2007, 50% (301/597) of cases were female.

Figure 18: Notification rate for shigellosis, Australia, 2007, by age and sex

The highest burden of shigellosis continues to be in Indigenous populations. Indigenous people make up 2% of the Australian population,¹⁶ however, 45% (269/596) of all shigellosis cases in 2007 were known to be Indigenous (indigenous status was known for 77% of cases). In the Northern Territory, 84% (146/173) of shigellosis cases were Indigenous (indigenous status was known for 97% of cases in the Northern Territory) and in South Australia 48% (30/62) were Indigenous (indigenous status was known for 79% of cases in South Australia).

The most common biotypes in 2007 were Shigella sonnei biotype a (21%) and Shigella sonnei biotype g (16%). In 2007, these 2 biotypes increased in number and proportion of notified cases compared with 2006.¹⁴ In 2006, the most common biotype was Shigella flexneri 4a mannitol negative.¹⁴

Faecal-oral transmission is known to be a common source of infection for shigellosis.¹⁷ Foodborne outbreaks of shigellosis are rare, and in 2007 there was only 1 foodborne outbreak of shigellosis, affecting 55 people. This outbreak was associated with imported fresh produce.^{14, 18}

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Shiga toxin-producing Escherichia coli

In 2007, there were 107 cases of STEC, a crude rate of 0.5 notifications per 100,000 population and an increase of 65% compared with an annual mean of 0.3 notifications per 100,000 population per year between 2002 and 2006.¹⁴

STEC rates were highest in South Australia (2.2 cases per 100,000 population) and the Northern Territory (1.4 cases per 100,000 population). South Australia reported 38% (41/107) of all STEC notifications, followed by Queensland (22%, 24/107), New South Wales (22%, 23/107), Victoria (12%, 13/107), the Northern Territory (2.8%, 3/107), Western Australia (2%, 2/107) and the Australian Capital Territory (1%, 1/107).

Jurisdictions use different methods in their screening of stools for STEC diagnosis, which can affect notification rates. As in previous years, in 2007 South Australia routinely tested all bloody stools by polymerase chain reaction (PCR) for genes coding for Shiga toxin. Queensland conducts routine culture on bloody stools. If there is no growth in culture, PCR is not performed, instead, ELISA for Shiga toxin is conducted on the specimen. Other jurisdictions do not routinely screen for STEC.

The highest age specific notification rate for STEC was amongst children in the 0–4 years age group (1.5 cases per 100,000 population), with peaks in older ages as well, with 1.0 cases per 100,000 population amongst the 60–65 years age group and 0.8 notifications per 100,000 population amongst the 70–74 years age group.¹⁴

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Typhoid

There were 90 cases of Salmonella Typhi infection (typhoid) during 2007 compared with a mean of 65 cases per year between 2002 and 2006. Overseas travel is a significant risk factor for typhoid infection in Australia; in 2007, 92% (83/90) of cases reported overseas travel (Table 13).

Table 13: Travel status for notified cases of typhoid, Australia, 2007

State or territory	History of overseas travel			Total
	Yes	No	Unknown
Australian Capital Territory	0	0	0	0
New South Wales	32	1	1	34
Northern Territory	2	1	0	3
Queensland	4	1	1	6
South Australia	5	0	0	5
Tasmania	3	0	0	3
Victoria	30	0	0	30
Western Australia	7	2	0	9
Total	83	5	2	90

More than half of all overseas-acquired cases reporting overseas travel had travelled to India (51%, 42/83), with Bangladesh the second most frequently reported country or region with 13% (11/83) of cases. The predominant phage types isolated from cases returning from travel to India were E1 (19 cases) and E9 (9 cases). Similarly in cases returning from travel to Bangladesh, the most common infecting phage type was E9 (4 cases).

The highest typhoid notification rates were in the 20–24 years age group, with 0.8 cases per 100,000 population and in the 25–29 years age group with 1.1 cases per 100,000 population (Figure 19), compared with the overall notification rate of 0.4 cases per 100,000  population. This is likely to be due to high rates of overseas travel in these age groups.

Figure 19: Notifications of typhoid, Australia, 2007, by age group