Every year, the EU takes a concerted action to look at a particular food product or contaminant. This year, it is smoked fish and listeria.
In the fourth quarter of this year the Food Safety Authority of Ireland, and its sister organisations throughout the EU, will examine samples of smoked fish to determine their listeria content.
Listeria monocytogenes has been around for more than 100 years, but has only recently started to cause food poisoning in humans.
Why is it suddenly a problem? Dr Wayne Anderson, chief specialist (food science) with the Food Safety Authority, says it is because we have moved to what is known as "chilled chain distribution" of food.
This was a response to concerns about E numbers in foods. People wanted fresher products of higher quality, and a lot of producers moved towards chilling: with a chill temperature of less than 5C, fewer preservatives could be used.
Unfortunately, listeria monocytogenes can survive and grow at temperatures as low as 3C. "It can survive in the environment of a food processing establishment. Processing establishments are wet places and it doesn't need much to grow," says Dr Wayne Anderson. It can continue growing in supermarket and corner-shop fridges. Many of the products it grows in have shelf lives as long as three weeks.
It was believed for a time that very low numbers of bugs could cause problems, but this is no longer the thinking. However, the US has implemented a zerotolerance strategy: if there are any listeria at all in 25g of product tested, then the food is recalled.
In the EU a new piece of legislation, setting limits for listeria, is under discussion. "In essence, the consumer can't be exposed to more than 100 listeria per gram of final product, at the end of the product's shelf life," says Dr Anderson.
This will limit the numbers of the bug in ready-to-eat foods, but shouldn't lead to massive recalls. "I think it's a good compromise. It's not quite as draconian as the US but it's focusing on the area." Dr Wayne Anderson says the US zero-tolerance policy in raw minced beef may lead to a lot more food being thrown away than is strictly necessary, since mince is not eaten raw.
Listeria has been found in at least 37 mammalian species, both domestic and wild, as well as 17 species of birds and, possibly, some species of fish and shellfish. It can be isolated from soil, silage and other environmental sources. It is quite hardy and resists freezing, drying and heat quite well.
Healthy individuals can get listeriosis and be unaware they have the disease. They might suffer some mild influenza-like symptoms. But complications can include blood poisoning, meningitis, encephalitis and intrauterine or cervical infections in women, which may result in miscarriage in the second or third trimester. In cases of meningitis caused by listeria, mortality may be as high as 70 per cent.
Listeriosis can only be positively diagnosed by culturing the organism from blood, cerebrospinal fluid or stool. In the US there are an estimated 415 deaths a year. Most cases are sporadic, making links to food very difficult.
Those most at risk are pregnant women, who should avoid soft cheeses and smoked fish, says Dr Anderson. Immuno-supressed people, cancer patients and the elderly may also be vulnerable.
Bacteria such as listeria and the others discussed in this series (salmonella, E. coli 0157 and campylobacter) are not the only cause of food poisoning. Other bacteria and viruses have also been implicated.
There have been seven outbreaks of suspected viral food poisoning in the Republic since the beginning of this year, according to Dr Thomas Quigley, chief consultant in food safety with the Food Safety Promotion Board. These were not necessarily due to food. One hotel in the south of Ireland had to close. The origin of this outbreak could not be determined.
Small Round Structured Viruses can be food-borne from shellfish (which may be contaminated with human sewage) or when infected food handlers inadvertently infect food. But it is difficult to pinpoint the source of most outbreaks as passage from person to person is so easy. In this respect, SRSVs differ from the other four bugs discussed in this series.
With Small Round Structured Viruses, patients vomit spontaneously but don't necessarily get diarrhoea, he explains. If curtains and carpets are splashed by vomit, the virus can stay alive in these fabrics for between six and eight weeks. It is highly infectious and can be passed from person to person, either through direct contact or aerosols. There is a very short incubation period.
Most outbreaks occur in restaurants, hotels, nursing homes and hospitals, says Dr Quigley. Viruses are difficult to identify, requiring techniques such as electron microscopy or molecular typing. Luckily, SRSV is self-limiting, lasting only about two days.
There is an economic cost to outbreaks. For instance, Dr Quigley says that closing one ward in a hospital in Australia was costed at £3,800, with a further £5,300 for bed closures. There hasn't be any similar costing exercise here, he said.
How do you protect yourself against SRSVs? Simple: adequate cooking kills the virus, Dr Quigley says.
While consumers can take precautions when they store and cook foods themselves, Irish people eat about one quarter of their food outside the home. Dr Wayne Anderson says no food handler should work in food premises if they are suffering from gastroenteritis. They should be certified fit for work by a GP before returning.
"Infected food-handlers can spread infection to the foods they handle and this is especially an issue with SRSVs, Salmonella, Campylobacter and E.coli 0157," he said.
In February, the North Eastern Health Board became the first health board to launch an awareness campaign to stress to food businesses in its catchment area that they have a legal responsibility to ensure they serve safe food.
Over the past two years, there were almost 250 cases of food poisoning in counties Meath, Louth, Cavan and Monaghan, with 275 formal complaints and more than 1,300 formal actions taken against premises.
Dr Patrick Wall, chief executive of the Food Safety Authority of Ireland, says: "Foodborne illness results from poor hygiene and food-handling practices. We would urge consumers to vote with their feet - if they witness sub-standard practices they should complain to the management and take their custom elsewhere. Environmental health officers, together with consumers using their purchasing power, can effectively stamp out bad practice."
Food isn't fit for consumption if "it appears to be contaminated with chemicals such as disinfectants or detergents; it contains a foreign object such as hair or insects; hot food isn't piping hot; ready-to-eat food is in contact with raw meats or fish; fridges are not cold.
"Hygiene is poor if the shop or restaurant is visibly dirty; staff handling open food also handle money or other goods without washing hands or removing gloves; staff handle raw meats or fish and then other ready-to-eat foods without washing their hands; staff have dirty hands or smoke near food."
Complain to whoever is serving, to the manager, the local environmental health officer in the health board or the Food Safety Authority of Ireland.
Series concluded