The anatomy of an outbreak | Sumfood

Posted in Consumer on Oct 30, 2018

Speak to any food safety specialist and they will tell you that no two foodborne illness outbreaks are the same. That being said, they do tend to follow a pattern (food is contaminated, people get sick, authorities investigate, food products are recalled, investigation into the cause, and then legal action, if appropriate). How do authorities know when something is an outbreak and not just a coincidence that a group of people have become ill? The implications of misidentification are serious – if it isn’t an outbreak and a recall is demanded, it will have significant cost to the producer; or, worse still, when an outbreak is not identified, and more people become ill or die as a result.

The CDC consider that when two or more people get sick from eating the same contaminated food or drink, then the event is called a foodborne illness outbreak. At first glance this would seem to be a very low threshold, but it is very difficult to determine that the illness is a foodborne illness and that the cases are linked.

How many people have ever kept a food diary? It’s a simple concept, that is, until you start to write down everything you eat. It becomes increasingly complex when you consider where the different elements came from (the bagged salad was from here, the cold meat from there, and so on). Now, try and do that in retrospect, while feeling ill (possibly between gastrointestinal bathroom bouts). Getting accuracy of food inputs and piecing together the history that enables the accurate diagnosis of an outbreak is a job for food detectives. Of course, the authorities first must be notified that someone is sickened by a foodborne illness – it is difficult to extrapolate how many people ‘ride out’ an illness without seeking medical attention (and, of course, age, type of illness, underlying ill-health all have an impact on who seeks medical help). The CDC estimate that 48 million people (in the US) get sick from a foodborne illness each year, 128,000 are hospitalised and 3,000 die. It is fair to assume that not all 48 million cases of illness are reported, let alone, investigated.

For the purposes of this paper let’s assume that someone has become ill from eating a particular food product, they have sought medical help and that the medical professional has alerted the health authorities that a patient has been diagnosed with a foodborne illness (which was confirmed by laboratory test). What happens next is the health authorities swing into action looking for similar patterns of illness – has anyone else reported the same sickness? They look to see whether unrelated people have reported the same illness after eating at the same restaurant, café, supermarket; sick people are interviewed to look for foods that are common across those who are sickened or foods that appear more often than would be expected. Once common food(s) are identified, the authorities can then undertake a ‘trace back’ analysis – retracing the footsteps of the food to understand where contamination could have occurred. Along the way, samples are obtained and are analysed for the presence of the germ that has caused the illness. This process also highlights any risks in the supply chain – vulnerabilities that might allow future contamination to occur.

An interesting thing about the germs that cause foodborne illnesses is the ability for investigators to look at the DNA of the germ found in a food product alongside the DNA of the germ found in samples from patients and determine if it is the same. This provides certainty about whether someone has become ill from eating that particular food product from that particular manufacturer, restaurant or supermarket.

After positively identifying that there is a foodborne illness outbreak, confirming it through laboratory diagnosis and tracing it back to the source, then action can be taken to stop the spread of the contaminated product. It is at this point that the public is advised not to consume the identified product and food recalls are issued. Sometimes, a manufacturer may become concerned about a product and issue a voluntary recall before the investigation is complete. The health authorities may also force a temporary closure of the food production premises until they are satisfied that all further risk of contamination has been addressed.

So, what can you do to help prevent the spread of foodborne illnesses? While it seems a complicated process, if you become sick and think it may be from a foodborne illness, please, let your doctor know. Your doctor then has a record of the food you ate, and when, and from where. If more people become sick, then the process can start to determine whether cases are related and then to identify steps required to keep consumers safe.

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