Trends in food-borne disease.

Food-borne disease is widespread around the world, with its most serious consequences affecting those who are young, old and already ill. Chemical contaminants are present in much of the food supply but usually at levels not associated with adverse human effects. However, there are occasional problems from natural toxins that can cause local disease and restrict international trade. Much of food monitoring is focused on testing foods to meet the national standards for mycotoxins and pesticide residues. More recently, there have been concerns over specific chemicals such as acrylamide, food dyes and melamine as well as allergens, but there is no routine testing for these chemicals. Despite this concern over chemicals and their monitoring, most of the known illness relates to microbial contamination, and surveillance systems focus on that which links to human illness. Interestingly, many foods that have been associated with outbreaks would not have been thought of as vehicles from the then-existing microbiological studies, e.g. <i>Salmonella</i> in chocolate and peanut butter; <i>Escherichia coli</i> O157:H7 in apple cider and sprouts and <i>Listeria monocytogenes</i> in hot dogs. Many steps have to be taken to bring a food-borne disease outbreak investigation to a successful conclusion. As is so often the case, if key data are missing or the different players in the investigation do not coordinate effectively, not only will many ill persons not be identified, but also the cause of the outbreak may not be determined. Surveillance can comprise two main systems: complaint or notification systems, and pathogen-specific surveillance. The former may trigger an investigation and the latter leads to interpretation of case trends over periods of time. More recently there has been interest in syndromic surveillance as a way of rapidly detecting an event even if the causative agent may not yet been identified. Most countries have some kind of disease surveillance system and these usually include enteric diseases but not necessarily food-borne disease <i>per se</i>. Among those countries that do, they tend to have their own approach to surveillance, which is mainly passive in letting the local investigators prepare the reports and communicate these to national levels. An important step in food-borne disease surveillance is the development and maintenance of an active system, such as FoodNet and PulseNet in the USA, even if it is time-consuming and expensive. This is because they can be very useful in predicting the burden of food-borne disease at the national level and what the main risk factors are that lead to infections, which in turn help direct control measures. A new concern today is the threat of deliberate contamination of food, and early disease detection systems that link to first responders are being developed. In preparation for such an event, not only do public health personnel need to be involved, but also law enforcement officers who have a different mandate. This threat is stimulating better traceability methods particularly for imported foods, and having governments and industry being more concerned over fraud, counterfeiting and smuggling. Eventually, food-borne disease surveillance systems will become integrated internationally, as they are starting to do within Europe and under the direction of the World Health Organization.