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Outbreak Investigation

Navenia Wellington

Thursday, October 01, 2020

It has been clearly established that foodborne illnesses can occur from the consumption of any food that is contaminated with bacteria, toxins, viruses, parasites or chemicals. Also, when one person falls ill after consuming food the occurrence is classified as food poisoning, and where two or more persons have similar symptoms this may be classified as a foodborne illness outbreak. A third fact is foodborne illness remains a major public health concern globally.

Foodborne illnesses remain a public concern because we live in an ever-changing dynamic. For instance, influences such as eating out more, globalisation of supply chains, a borderless world for travellers and increases in the number of vulnerability in the population are contributory factors. According to the Canadian Government's website, an estimate of 4 million (1 in 8) Canadians are affected by a foodborne illness annually. The Centres for Disease Control and Prevention estimates that 48 million (1 in 6) Americans are affected each year. Both countries link their cases to 30-31 bacteria, parasites and viruses. The European Centre for Disease Prevention and Control in December 2019 reported that its member states in 2018 had 5,146 outbreaks which affected 48,365 persons. These countries were able to state the effect of foodborne illnesses as a result of an outbreak investigation.

The chief goals of an outbreak investigation are to:

1. Stop current outbreak as soon as possible by implementing effective control measures.

2. Prevent similar outbreaks in the future — an opportunity to identify gaps in the food safety system. 

These goals are achieved by the steps as summarised below:

1. Preliminary assessment of the situation — to determine if:

a. the cases have the same illness

b. there is a real outbreak

2. Communication — best routes to use. Who, What, When, Why and How. Embrace social media

3. Descriptive epidemiology — establish case definition, identify as many cases as possible

4. Food and environmental investigations

a. Inspect implicated food business

b. Collect food and environmental samples

5. Analyse and interpret data

a. Review all existing data

b. Develop and test hypotheses

6. Control measures

a. Control source of outbreak

b. Control transmission

c. Protect at-risk persons

7. Further studies

a. Such as case-control and cohort studies

b. Recommend preventive measures

c. Share information to promote awareness and to prevent reoccurrence 

It is important to note that an outbreak investigation cannot be a “one-man show”. The World Health Organization (WHO) states it best in their Foodborne Disease Outbreaks Guidelines for Investigation and Control: “The investigation and control of foodborne disease outbreaks are multi-disciplinary tasks requiring skills in the areas of clinical medicine, epidemiology, laboratory medicine, food microbiology and chemistry, food safety and food control, and risk communication and management.” The current management of COVID-19 effectively demonstrates that a multi-disciplinary approach is in keeping with WHO. When conducting an outbreak investigation, the cycle of foodborne illness control and prevention is a part of the road map. This includes surveillance, epidemiologic investigation, preventative measures and applied research. 

The scale of the outbreak may be local (within a community), national or international; this is linked to the number of cases and severity level of symptoms. An example of international cases currently is the ongoing salmonella outbreak investigations across the United States and Canada linked to peaches and red onions. While an example of national is the salmonella outbreak in Canada linked to frozen raw breaded chicken products.