This article was published in Communicable Diseases Intelligence Vol 35 Number 2, June 2011 and may be downloaded as a full version PDF file (1854 KB).
Results, cont'd
Gastrointestinal diseases
In 2009, gastrointestinal diseases notified to NNDSS were: botulism, campylobacteriosis, cryptosporidiosis, haemolytic uraemic syndrome (HUS), hepatitis A, hepatitis E, listeriosis, salmonellosis, shigellosis, Shiga toxin-producing Escherichia coli (STEC) infections and typhoid.
Overall notifications of gastrointestinal diseases increased 16% from 27,308 in 2008 to 31,697 in 2009. Notifications of cryptosporidiosis, hepatitis A, listeriosis and STEC were notably increased compared with the 5-year mean (exceeded the mean by more than 2 standard deviations).
Australia’s enhanced foodborne disease surveillance network, OzFoodNet, monitors the incidence of diseases caused by pathogens commonly transmitted by food, using population-based passive and enhanced surveillance for notifiable gastrointestinal diseases and for outbreaks of gastroenteritis and enteric disease. In 2009, OzFoodNet aggregated and analysed data from NNDSS, supplemented by enhanced surveillance data, on the following 9 diseases or conditions, a proportion of which may be transmitted by food: non-typhoidal salmonellosis, campylobacteriosis, listeriosis, shigellosis, typhoid, STEC infections, botulism, HUS and hepatitis A. The data and results from these analyses are summarised in the following sections but are reported in more detail elsewhere.22
Botulism
Botulism is a rare but extremely serious intoxication resulting from toxins produced by Clostridium botulinum (commonly toxin types A, B and E). Three forms of botulism are recognised; infant, foodborne and wound.21 Infant botulism occurs when C. botulinum spores are ingested, germinate in the infant’s intestine and the organism produces botulinum toxin. It does not include cases where the preformed toxin is ingested, these are considered foodborne.
One case of botulism was reported to NNDSS in 2009; an infant botulism case reported from Queensland.22 The case was hospitalised in intensive care with onset of symptoms (acute flaccid paralysis) in March 2009. C. botulinum toxin was detected in a stool sample and culture by mouse bioassay, and identified as toxin type B. The infant was entirely breast-fed and had not had a bowel motion for approximately 2 weeks prior to admission. It was speculated that the slow transit time within the bowel provided time for the toxin to develop. Treatment included human immunoglobulin for infant botulism obtained from the United States of America.
There were no notifications of botulism reported in 2008 and one in 2007.
Campylobacteriosis
Campylobacteriosis is notifiable in all Australian jurisdictions, except New South Wales.
In 2009, there were 15,973 notifications of campylobacteriosis, similar to the 15,535 notifications reported in 2008. The national rate of campylobacteriosis notifications was also similar to the previous year, with 108.1 notifications per 100,000 population in 2009 compared with 107.5 per 100,000 in 2008.
Notification rates were highest amongst males in nearly all age groups. The highest age specific rate for both males and females was in infants aged 1 year (343 and 233 notifications per 100,000 population, respectively) with additional peaks in the 20–29 and 70–84 year age-groups (Figure 15).
Figure 15: Notification rate for campylobacteriosis, Australia, 2009, by age group and sex. Inset: age and sex in children aged under 5 years
Cryptosporidiosis
In 2009, 4,625 notifications of cryptosporidiosis were reported to NNDSS, a national rate of 21.1 notifications per 100,000 population. This represents a 130% increase over the 2,003 notifications reported in 2008 and is the largest number reported since the disease became nationally notifiable in 2001 (Figure 16). Cryptosporidiosis notifications fluctuate from year to year, and notifications are most numerous in autumn and summer, with some regional variation.
Figure 16: Notifications of cryptosporidiosis, Australia, by month and year, 2001 to 2009. Inset: by month and state or territory
The highest notification rate was in the Northern Territory, with a rate of 66.7 per 100,000 population (150 notifications). There were 4 recognised outbreaks of cryptosporidiosis in the Northern Territory in 2009, all of them occurring in remote Indigenous communities.
The largest number of notifications was reported from New South Wales (1,463), where notifications were increased by 143% compared with the 5-year mean of 861 notifications for the state. This increase was due to a large outbreak of cryptosporidiosis associated with public swimming pools in early 2009. The NSW Department of Health (NSW Health) issued several public health alerts through the media, and NSW Health’s Environmental Health Branch worked with the owners of the affected swimming pools to reduce the risk of further transmission.
The completeness of the Indigenous status field nationally (47.9%) was too low for meaningful analysis, but in the Northern Territory, cases amongst Indigenous people accounted for 64.7% of notifications in 2009, with 94.7% data completeness.
In 2009, 52.9% of nationally notified cases were female. Forty per cent of all notified cases were in children aged under 5 years with notification rates higher amongst males in this age group (Figure 17).
Figure 17: Notification rate for cryptosporidiosis, Australia, 2009, by age group and sex. Inset: age and sex in children aged under 5 years
Haemolytic uraemic syndrome
Haemolytic uraemic syndrome is a rare but serious disease, related to some gastrointestinal infections, and results in chronic complications in 40% of cases.23 In 2009, there were 12 notifications of HUS (rate 0.05 per 100,000 population) (Table 3), compared with 31 in 2008 and a mean of 20 notifications per year (0.1 per 100,000 population) between 2004 and 2008.
The median age of HUS notifications was 10 years (range 1 to 89 years) and were most frequently reported amongst children aged 0–4 years (Table 11).
Table 11: Notifications of haemolytic uraemic syndrome, Australia, 2009, by age group
Age group |
Number of notifications |
|---|---|
| 0–4 | 4 |
| 5–9 | 2 |
| 10–14 | 2 |
| 15–19 | 0 |
| 20–24 | 0 |
| 25–29 | 1 |
| 30–34 | 0 |
| 35–39 | 0 |
| 40–44 | 0 |
| 45–49 | 0 |
| 50–54 | 0 |
| 55–59 | 0 |
| 60–64 | 1 |
| 65–69 | 0 |
| 70–74 | 0 |
| 75–79 | 1 |
| 80–84 | 0 |
| 85+ | 1 |
HUS can result from an antecedent STEC infection, but may be due to non-enteric infections, or non-infectious causes. An antecedent STEC infection was reported in 41.7% (5) of notified cases. One was associated with a non-Shiga toxin-producing E. coli infection, 1 case was associated with Streptococcus pneumoniae infection, and no aetiology was reported for the remaining 5 notifications.22
Hepatitis A
In 2009, there were 563 notifications of hepatitis A in Australia, a 104% increase compared with the 277 notifications in 2008 (Table 3). The rate of 2.6 notifications per 100,000 population compared with the 5-year mean of 0.3 per 100,000.22 This increase (Figure 18) was largely attributable to an outbreak of locally-acquired infections between 1 March 2009 and 18 March 2010, associated with the consumption of semi-dried tomatoes.22,24
Figure 18: Notifications of hepatitis A, Australia, 1991 to 2008, by year of diagnosis
Hepatitis A was most frequently notified amongst young adults (Figure 19). The median age of notified cases was 32 years (range 1–88 years). Half (50.4%) of all notified cases were female.
Figure 19: Notification rate for hepatitis A, Australia, 2009, by age group and sex
While overseas travel has been the most frequently reported risk factor for notified cases in recent years,25 in 2009 a higher than usual proportion of notified cases were locally-acquired (67% in 2009 compared with less than 45% between 2004 and 2008). This increase was due to the semi-dried tomato outbreak (Table 12).
Table 12: Notifications of hepatitis A, Australia, 2004 to 2009, by place of acquisition
| Locally acquired | Acquired overseas | Unknown | ||||
|---|---|---|---|---|---|---|
Year |
% | n | % | n | % | n |
| 2004 | 44.7 |
143 |
30.6 |
98 |
24.7 |
79 |
| 2005 | 36.7 |
121 |
31.8 |
105 |
31.5 |
104 |
| 2006 | 42.1 |
120 |
37.9 |
108 |
20.0 |
57 |
| 2007 | 30.5 |
50 |
57.9 |
95 |
11.6 |
19 |
| 2008 | 37.0 |
102 |
55.8 |
154 |
7.2 |
20 |
| 2009 | 67.0 |
377 |
30.4 |
171 |
2.7 |
15 |
The proportion of notifications of hepatitis A in Australia in Indigenous persons remains low, with only 1% of notifications in 2009 reported as Indigenous, compared with 10%–12% (37–53 notifications) per year between 2003 and 2006, and less than 2% in 2007 and 2008 (0 and 3 notifications respectively). Indigenous status was known for 92% of notifications in 2009. This marked decrease in recent years in the number and proportion of notifications who were Indigenous is likely to be due in part to targeted vaccination programs for Indigenous children commencing in north Queensland in 1999, and the provision of free hepatitis A vaccine for all Indigenous children in the whole of Queensland, South Australia, Western Australia and the Northern Territory from 2006 (Figure 18).26
Hepatitis E
In 2009, there were 33 notifications of hepatitis E, compared with 44 notifications in 2008. Hepatitis E in Australia is associated strongly with overseas travel, with 68% (30)27 and 89% (16/18)28 of notified cases in 2008 and 2007 respectively known to have been acquired overseas. Data on travel status were not collated nationally in 2009.
Listeriosis
Invasive listeriosis commonly affects the elderly or immunocompromised, and is most common amongst people with serious or terminal underlying illnesses, but also amongst pregnant women and their newborn babies. Foetuses may become infected in utero. Laboratory-confirmed infections in a mother and unborn child or a neonate are notified separately in the NNDSS. However, OzFoodNet counts such pairs as 1 case’, with the mother reported as the primary case, leading to differences in numbers from those reported here.
In 2009, 91 notifications of invasive Listeria monocytogenes infection were reported to NNDSS (0.4 per 100,000 population) compared with a 5-year historical mean of 60 notifications (0.3 per 100,000) (Figure 20). This increase was in part due to a multi-jurisdictional outbreak of listeriosis that was associated with the consumption of contaminated chicken wraps.22
Figure 20: Notifications of invasive listeriosis, Australia, 2004 to 2009, by month and year
Seventeen of these 91 notified cases (19%) were pregnancy related, occurring in pregnant women and/or their newborn babies. In 2009, 55% (41/74) of the non-pregnancy related cases were female. Fifty-six per cent (51/91) of notifications were in people aged 60 years or more (this group forms 19% of the Australian population) and the highest age-specific notification rate was in people aged 85 years or more (12 notifications, 3.1 per 100,000 population).
Salmonellosis (non-typhoidal)
There were 9,533 notifications of salmonellosis in Australia in 2009 representing a rate of 43.6 notifications per 100,000 population, compared with a 5-year mean of 40.8 per 100,000.22 Notification rates ranged from 30 per 100,000 in Victoria to 217 per 100,000 in the Northern Territory. In 2009, 51% of notifications were in females. Children aged 0–1 year had the highest age specific notification rate (300 per 100,000).
Individual notifications are rarely attributed to a particular source. In Australia, Salmonella infections, and in particular serotype Typhimurium, frequently manifest as outbreaks transmitted via contaminated food, and investigation of these outbreaks provides information about high-risk foods to inform policy and regulation. In 2009, OzFoodNet epidemiologists investigated 60 foodborne or suspected foodborne outbreaks of salmonellosis, affecting 771 people, although not all of these were laboratory-confirmed cases.22 The most frequently reported Salmonella serotypes nationally were S. Typhimurium (32% of notified cases) and S. Enteritidis (18% of notified cases).
Shigellosis
In 2009, 622 notifications of shigellosis were reported, a rate of 2.8 per 100,000 population, similar to the 5-year mean of 3.1 per 100,000. As in previous years, the highest notification rate was in the Northern Territory (37.8 per 100,000), although this was lower than its 5-year mean (74.7 per 100,000).22 Shigella sonnei biotype g (33%; 207) was the most commonly reported biotype in 2009, followed by S. sonnei biotype a (19%; 118) (Figure 21).
Figure 21: Notifications of shigellosis, Australia, 2005 to 2009, by biotype
Notification rates for shigellosis were highest in males and females aged 0–4 years (10.7 and 8.1 per 100,000, respectively). Secondary peaks were observed in males aged 30–44 years, and in females aged 55–59 years. Amongst children under 5 years of age, the highest notification rates were in children aged 1 year (Figure 22).
Figure 22: Notification rate for shigellosis, Australia, 2009, by age group and sex. Inset: notifications in children aged under 5 years, Australia, 2009
Information on Indigenous status was available for 66.6% (414) of notifications. Data completeness on Indigenous status varied by state or territory, with the Australian Capital Territory, New South Wales, Queensland, and South Australia being less than 85% complete. Amongst jurisdictions with greater than 85% completeness, the proportion of notified cases who identified as being of Aboriginal or Torres Strait Island origin was 48.6% (142/292).
Information on overseas travel status as a risk factor was available for 47.4% (295/622) of notified cases, with 45.8% (135/295) of these reporting overseas travel during the time when they were likely to have been exposed to the infection (Table 13). The most frequently reported countries of acquisition for imported cases were Indonesia (29.6%, 40/135) and India (11.9%, 16/135).22
Table 13: Notifications of shigellosis, Australia, 2009, by overseas travel status
| Overseas travel | |||||
|---|---|---|---|---|---|
State or territory |
Yes | No | Not stated/unknown | Overseas acquired (%) | Total |
| ACT | 6 |
2 |
0 |
75.0 |
8 |
| NSW | 10 |
1 |
145 |
6.4 |
156 |
| NT | 2 |
4 |
79 |
2.4 |
85 |
| Qld | 20 |
48 |
47 |
17.4 |
115 |
| SA | 28 |
11 |
12 |
54.9 |
51 |
| Tas | 2 |
0 |
0 |
100.0 |
2 |
| Vic | 39 |
40 |
6 |
45.9 |
85 |
| WA | 28 |
54 |
38 |
23.3 |
120 |
| Total | 135 |
160 |
327 |
21.7 |
622 |
Shiga toxin-producing Escherichia coli infections
There were 130 notifications of STEC in Australia in 2009,, a rate of 0.6 notifications per 100,000 population (Table 3) compared with the 5-year mean of 0.4 per 100,000.22 Thirty-one per cent (40) of notifications in 2009 were known to have been associated with 3 jurisdictional outbreaks and a multi-jurisdictional cluster, which may in part explain the higher overall rate.
Rates of STEC infection are strongly influenced by jurisdictional practices regarding the screening of stool specimens.29 In particular, South Australia routinely tests all bloody stools by polymerase chain reaction (PCR) for genes coding for Shiga toxins and other virulence factors, making rates for this state the highest in the country at 3.9 per 100,000 population.
In 2009, 56.9% of notified cases were female. The median age of notified cases was 44 years (range 0–91 years). Age specific notification rates were highest in younger (0–19 years) and older (55 years or older) age groups, with 35.4% (46/130) and 41.5% (54/130) respectively falling into these age groups (Figure 23).
Figure 23: Notification rate for Shiga toxin-producing Escherichia coli, Australia, 2009, by age group
Typhoid
There were 115 notifications of S. Typhi infection (typhoid) during 2009 (0.5 per 100,000 population), which was slightly higher than the 5-year mean of 0.4 per 100,000.22
Similar to previous years, overseas travel was the primary risk factor for notified cases in 2009, with 88.7% (102/115) of notified cases known to have been acquired overseas, compared with 92.3% (97/105) in 2008.27 India continues to be the most frequently reported country of acquisition, accounting for 61.8% (63/102) of overseas acquired cases in 2009, with a range of other countries in South and South East Asia reported as the place of acquisition, each by less than 1% of cases.
Age specific notification rates were highest in the 25–29 years age group (1.6 per 100,000 population) and the 20–24 years (1.1 per 100,000) age group (Figure 24), reflecting higher rates of overseas travel in young adults.
Figure 24: Notification rate for typhoid, Australia, 2009, by age group
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This issue - Vol 35 No 2, June 2011
NNDSS Annual report 2009