Gillian Hall

Does ambient temperature affect foodborne disease

Background: Foodborne illness is a significant public health issue in most countries, including Australia. We examined the association between temperature and salmonellosis notifications, and compared these associations for 5 Australian cities. Methods: Log-linear models describing monthly salmonellosis notifications in terms of calendar time and monthly average temperatures were fitted over the period 1991 to 2001 for each city. We used a negative binomial chance model to accommodate overdispersion in the counts. Results: The long-term trend showed an increase in salmonellosis notifications in each of the 5 cities. There was a positive association between monthly salmonellosis notifications and mean monthly temperature of the previous month in every city. Seasonal patterns in salmonellosis notifications were fully explained by changes in temperature. Discussion: The strength of the association, the consistency across 5 cities, and a plausible biologic pathway suggest that higher ambient temperatures are a cause of higher salmonellosis notifications. The lag of 1 month suggests that temperature might be more influential earlier in the production process rather than at the food preparation stage. This knowledge can help to guide policy on food preparation and distribution. It also suggests a basis for an early warning system for increased risk from salmonellosis, and raises yet another possible health problem with global warming.

Internationally Distributed Frozen Oyster Meat Causing Multiple Outbreaks of Norovirus Infection in Australia

BACKGROUND Between November 2003 and January 2004, outbreaks of norovirus in 3 Australian jurisdictions involving 83 cases of illness were associated with imported oyster meat. METHODS Cohort studies were conducted in 2 jurisdictions to identify relative risks of illness for the consumption of oysters. A case series was conducted in the third jurisdiction. RESULTS The cohort studies conducted in the first 2 jurisdictions identified relative risks of illness of 17 (95% confidence interval, 5-51) and 35 (95% confidence interval, 5-243), respectively, for the consumption of oysters. Multiple strains of norovirus were detected in fecal specimens from 8 of 14 patients and in 1 of the 3 batches of implicated oyster meat using seminested reverse-transcriptase polymerase chain reaction methods. Traceback investigations revealed that all oyster meat was harvested from the same estuary system in Japan within the same month. CONCLUSIONS These outbreaks demonstrate the potential of foodborne disease to spread internationally and the need for national and international collaboration to investigate such outbreaks. Foodborne illness related to norovirus is underestimated because of underreporting of human cases and challenges in laboratory detection of viruses in foods, both of which can delay public health action.

Population-Attributable Risk Estimates for Risk Factors Associated with Campylobacter Infection, Australia

One-sentence summary: Each year, an estimated 50,500 cases in persons >5 years of age can be directly attributed to consumption of chicken.

A common, symptom-based case definition for gastroenteritis

National studies determining the burden of gastroenteritis have defined gastroenteritis by its clinical picture, using symptoms to classify cases and non-cases. The use of different case definitions has complicated inter-country comparisons. We selected four case definitions from the literature, applied these to population data from Australia, Canada, Ireland, Malta and the United States, and evaluated how the epidemiology of illness varied. Based on the results, we developed a standard case definition. The choice of case definition impacted on the observed incidence of gastroenteritis, with a 1.5-2.1 times difference between definitions in a given country. The proportion of cases with bloody diarrhoea, fever, and the proportion who sought medical care and submitted a stool sample also varied. The mean age of cases varied by <5 years under the four definitions. To ensure comparability of results between studies, we recommend a standard symptom-based case definition, and minimum set of results to be reported.

Epidemiology of Shiga toxin producing Escherichia coli in Australia, 2000-2010

BackgroundShiga toxin-producing Escherichia coli (STEC) are an important cause of gastroenteritis in Australia and worldwide and can also result in serious sequelae such as haemolytic uraemic syndrome (HUS). In this paper we describe the epidemiology of STEC in Australia using the latest available data.MethodsNational and state notifications data, as well as data on serotypes, hospitalizations, mortality and outbreaks were examined.ResultsFor the 11 year period 2000 to 2010, the overall annual Australian rate of all notified STEC illness was 0.4 cases per 100,000 per year. In total, there were 822 STEC infections notified in Australia over this period, with a low of 1 notification in the Australian Capital Territory (corresponding to a rate of 0.03 cases per 100,000/year) and a high of 413 notifications in South Australia (corresponding to a rate of 2.4 cases per 100,000/year), the state with the most comprehensive surveillance for STEC infection in the country. Nationally, 71.2% (504/708) of STEC infections underwent serotype testing between 2001 and 2009, and of these, 58.0% (225/388) were found to be O157 strains, with O111 (13.7%) and O26 (11.1%) strains also commonly associated with STEC infections. The notification rate for STEC O157 infections Australia wide between 2001-2009 was 0.12 cases per 100,000 per year. Over the same 9 year period there were 11 outbreaks caused by STEC, with these outbreaks generally being small in size and caused by a variety of serogroups. The overall annual rate of notified HUS in Australia between 2000 and 2010 was 0.07 cases per 100,000 per year. Both STEC infections and HUS cases showed a similar seasonal distribution, with a larger proportion of reported cases occurring in the summer months of December to February.ConclusionsSTEC infections in Australia have remained fairly steady over the past 11 years. Overall, the incidence and burden of disease due to STEC and HUS in Australia appears comparable or lower than similar developed countries.

Crowding and other strong predictors of upper respiratory tract carriage of otitis media-related bacteria in Australian aboriginal and non-aboriginal children

Background: Streptococcus pneumoniae, Moraxella catarrhalis, and nontypeable Haemophilus influenzae is associated with otitis media (OM). Data are limited on risk factors for carriage of these pathogens, particularly for Indigenous populations. We investigated predictors of nasopharyngeal carriage in Australian Aboriginal and non-Aboriginal children. Methods: Nasopharyngeal aspirates were collected up to 7 times before age 2 years from 100 Aboriginal and 180 non-Aboriginal children. Longitudinal modeling estimated effects of environmental factors and concurrent carriage of other bacteria on the probability of bacterial carriage. We present a novel method combining the effects of number of household members and size of house into an overall crowding model. Results: Each additional household member increased the risk of carriage of S. pneumoniae (odds ratio [OR] = 1.45 per additional Aboriginal child in a 4-room house, 95% confidence interval [CI]: 1.15–1.84; OR = 2.34 per additional non-Aboriginal child, 95% CI: 1.76–3.10), with similar effect sizes for M. catarrhalis, and nontypeable Haemophilus influenzae. However, living in a larger house attenuated this effect among Aboriginal children. Daycare attendance predicted carriage of the 3 OM-associated bacteria among non-Aboriginal children. Exclusive breast-feeding at 6 to 8 weeks protected against Streptococcus aureus carriage (OR = 0.42, 95% CI: 0.19–0.90 in Aboriginal children and OR = 0.49, 95% CI: 0.25–0.96 in non-Aboriginal children). OM-associated bacteria were more likely to be present if there was concurrent carriage of the other OM-associated species. Conclusions: This study highlights the importance of household transmission in carriage of OM bacteria, underscoring the need to reduce the crowding in Aboriginal households.

Estimating Community Incidence of Salmonella, Campylobacter, and Shiga Toxin-producing Escherichia coli Infections, Australia

Estimated multipliers that linked surveillance of foodborne diseases with community incidence showed a high prevalence of these diseases.

Foodborne Illness, Australia, Circa 2000 and Circa 2010

Overall incidence of foodborne gastroenteritis declined but remains high, and the incidence of salmonellosis and campylobacteriosis increased.

Gastroenteritis and Food-Borne Disease in Elderly People Living in Long-Term Care

Elderly people in long-term care facilities (LTCFs) may be more vulnerable to infectious gastroenteritis and food-borne disease and more likely to experience serious outcomes. We review the epidemiology of gastroenteritis and food-borne diseases in elderly residents of LTCFs to inform measures aimed at preventing sporadic disease and outbreaks. Gastroenteritis in elderly people is primarily acquired from other infected persons and contaminated foods, although infections may also be acquired when residents have poor personal hygiene, have contaminated living environments or water, or have contact with infected pets. Early recognition of outbreaks and implementation of control measures is critical to reduce the effects on LTCF residents and staff members. Although outbreaks among LTCF residents are common, they are challenging to investigate, and there are still major gaps in our knowledge, particularly in regards to controlling noroviruses, the incidence and causes of specific infections, and sources of food-borne disease.

Surveillance for outbreaks of gastroenteritis in long-term care facilities, Australia, 2002-2008.

BACKGROUND Each year in Australia, health departments investigate hundreds of gastroenteritis outbreaks. Long-term care facilities (LTCFs) for elderly persons are a common setting for these outbreaks and can result in potentially serious outcomes. METHODS We established surveillance for gastroenteritis outbreaks in 2001, and analyzed data on outbreaks occurring from 1 July 2002 through 30 June 2008 to estimate the incidence in Australian LTCFs and residents. We summarized outbreaks by mode of transmission and etiological agent. We used negative binomial regression to examine variation in the number of fecal specimens collected in outbreaks-a marker of investigation intensity. RESULTS During surveillance, 3257 (52%) of 6295 outbreaks of gastroenteritis and foodborne disease in Australia were reported in LTCFs. These outbreaks affected 84,769 people, with 1577 people hospitalized and 209 deaths. There were 0.19 (95% confidence interval, 0.14-0.26) residents affected per 1000 bed days and 16.8 (95% confidence interval, 12.4-22.7) outbreaks per 100 LTCFs annually. LTCF outbreaks were most commonly transmitted from person to person. Only 43 (1.3% ) of 3257 outbreaks were foodborne, although 47 (6.4%) of 733 residents were hospitalized and 20 (2.7%) of 733 died. Norovirus was responsible for 1136 (35%) of all 3257 outbreaks. Higher numbers of fecal specimens per outbreak were collected in 4 Australian States, in later years of surveillance, and where the etiology was identified. CONCLUSIONS Norovirus outbreaks spread from person to person are common in LTCFs, although clinicians should be alert for foodborne outbreaks with more serious consequences. There is a need to identify effective infection control measures to assist facilities in managing outbreaks of gastroenteritis.