Food poisoning on the rise as diets change

Not so fresh: Food poisoning has been increasingly traced back to fresh produce.
Not so fresh: Food poisoning has been increasingly traced back to fresh produce. Photo: Chris Elfes

The number of Australians struck down by food poisoning has leapt almost 80 per cent in the past decade and the number of outbreaks linked to restaurants has more than doubled, according to the latest government statistics.

As investigators grapple to find the cause behind what is potentially the largest outbreak of salmonella poisoning the ACT has ever seen, experts warn that changing diets, demographics and an increasingly globalised food supply will continue to present challenges to public health security systems.

In the decade to 2011, the number of Australians affected by food-borne gastroenteritis increased 79 per cent, according to figures from OzFoodNet, the national food-borne disease monitoring network. In 2011, 150 outbreaks affecting 2241 people were recorded, compared to 86 outbreaks affecting 1768 people in 2001. The rate of hospitalisation has also increased, from 4 per cent in 2001 to 10 per cent in 2011.

These figures capture only a fraction of actual infections since most people with gastroenteritis don't go to a doctor, experts say. A 2002 estimate of the true number of people affected by food poisoning put the number at 5.4 million cases of gastro and 120 deaths per year, with an economic burden of $1.25 million. These figures are currently being revised to take into account recent trends.

Changing diets

While the increased incidence of food poisoning has been linked to multiple factors, changing eating habits is believed to be a leading cause.

Raw and minimally-cooked eggs are the "single largest cause" of the rise in salmonella poisoning, according to the ...
Raw and minimally-cooked eggs are the "single largest cause" of the rise in salmonella poisoning, according to the national foodborne disease monitoring network. Photo: Supplied

People are cooking less and eating out more, which may help to explain why the food service industry was responsible for more than three-quarters of food poisoning outbreaks in 2011, according to OzFoodNet figures.

“Traditionally food is prepared and eaten immediately, but now food might be prepared and left longer before,” says CSIRO food microbiologist Cathy Moir.

“Because we're making these foods more available, the exposure to the population is greater, whereas if someone made it in their home and fed it to their family, the organism is only being exposed to five people rather than 500.”


Whether cooked in the home or in a restaurant, the decades-long rise in campylobacter infection has been attributed to a shift in preference towards chicken meat, with contamination by raw or undercooked chicken a major cause. But it's not the only dietary change that has had repercussions for food-borne illness.

“There used to be a saying that it's always the chicken," says Martyn Kirk, a senior lecturer in epidemiology at the Australian National University and former OzFoodNet senior epidemiologist. "It's definitely not always the chicken."

"We've had outbreaks of salmonella linked to rockmelon, papaya, cucumbers. And we know that's just the tip of the iceberg,” says Kirk.

A lot of the problem would be fixed if we just washed our hands. Every single person in the food chain has to be aware of what they're doing.

The dramatic rise in salmonella poisoning in the past decade “is quite telling,” he says. Salmonella poisoning has jumped 38 per cent since 2001, according to the national surveillance system for notifiable diseases. The single largest cause: raw or minimally cooked eggs.

“At the time [of the rise] and prior to that, there was an increase in popularity of raw egg-based dishes like aioli and of desserts containing raw eggs,” Kirk says.

“The majority of dishes are safe and don't have salmonella on the surface, but once you start handling them – and handling them in a way that doesn't cook them – you're allowing more opportunities for salmonella to spread.”

Intensive farming has been linked to the emergence of new pathogens overseas.
Intensive farming has been linked to the emergence of new pathogens overseas. Photo: James Brickwood

This same principle applies to any food preparation that drops the bacterial "kill step" of cooking. Fresh produce has increasingly been implicated in food poisoning outbreaks – most notably in the US but also in Australia – as health-conscious consumers increasingly favour salads, raw vegetables and minimally processed foods with lower salt and fat contents.

However, its not just improperly prepared fresh produce that poses a risk. At the other end of the supermarket aisle, high-fat and high-sugar foods can enhance bacterial survival by protecting bacterial cells from stomach acid.

“The number of bacteria you're required to ingest to establish an infection of salmonella might be up to a thousand cells, but if those cells are in a high-fat or high-sugar food like chocolate, then you might need only 10 to 100 to contract an infection,” Kirk says.

A global context

Food-borne illness and public health security is a growing problem worldwide, with developing countries bearing the brunt of the burden. Part of the issue, public health experts say, is that food-borne illnesses are not only spreading further and faster; new pathogens are emerging and some strains are becoming harder to control.

The rise of intensive farming has been associated with the emergence of new pathogens, including a variant of the rare degenerative brain disorder Creutzfeldt-Jakob disease, sometimes referred to as the human form of "mad cow disease".

“It's an ongoing issue because with those farming practices you have a lot of animals in a pen; there's a problem with pollution of waterways and if farmers don't follow regulations and requirements then there's the potential for things to go wrong,” says industry consultant and former CSIRO food quality and safety director Patricia Desmarchelier.

But Australia's comparatively tough regulations and rigorous inspection regime has effectively limited the spread and incidence of food-borne disease, she says.

“Regulators are insisting food control must go right from the farm to consumers,” Desmarchelier says.

“With antibiotics, for example, there are some parts of the world where that's a huge problem… but the Australian government and industry have been quick to ban the use of growth promotants and ban or limit the use of particular antibiotics that are necessary for use in humans.”

So far, so safe. However, industry, government and the scientific community are bracing for the health security implications of increasingly global food production systems. As distribution networks continue to expand, for example, contaminated food acquires a global reach like never before – the consequences of which we are already feeling, Kirk says.

Back in 2002, for example, gastroenteritis outbreak linked to a kebab shop in NSW was eventually traced back to a tahini supplier in Egypt.

“Globalisation of food supply means we may be more likely to see infections we're not used to, like antibiotic-resistant strains or different types of food poisoning agents,” Kirk says. He adds, however, that such outbreaks "don't represent the bulk of outbreaks of food-borne disease”.

Changing demographics

Other battlefronts originate closer to home.

"An ageing  population, that's a huge challenge to us not just because older people are particularly susceptible but also because there are a whole lot of practices for elderly people that are different," Desmarchelier says.

Reduced mobility can mean elderly people shop less often, store food for longer and eat more pre-prepared food, which can put them at risk, she says. They also tend to have chronic ill health and poorer immune defences, while aged-care homes can be problematic because infections spread more easily between people living in close proximity.

Despite all these challenges, Food Safety Information Council CEO Juliana Madden says following one simple habit would go a long way.

"Honestly, a lot of the problem would be fixed if we just washed our hands," she says.