Why early detection of outbreaks is so important

Evidence

It has been estimated that there are 4 million cases of gastroenteritis in Canada each year.¹ Nationally, the most common microbial causes are Salmonella (40%), Escherichia coli (15%), and norovirus (12%), and the most common food source is meat,² although other sources like eggs and raw vegetables are also common. However, there are some unique aspects to enteric disease in Canadian indigenous populations. In a recent review on this topic, walrus, seal, caribou, and whale were the most common traditional foods tied to food-borne illness and were primarily associated with botulism and trichinosis. Raw food or food that had undergone fermentation were the most common traditional preparation methods linked to food-borne illness.³

This case exemplifies the synergy that can occur when primary care and public health work together and the affected community is an active partner in the response. If these patients were only stabilized medically, the outbreak might not be identified. Without a primary care physician notifying public health, the investigation might not be triggered. If the cause is not detected, then these types of infections can spread or recur. And unfortunately, this happens. However, when clinicians engage public health, and the source of the outbreak is identified, then the cause can be addressed and the health of the population improved.

The capacity to identify the cause of outbreaks is now greater than ever owing to new laboratory testing techniques. Using pulsed-field gel electrophoresis for DNA fingerprinting can identify the bacterium’s specific genetic pattern. This is especially useful in detecting outbreaks that occur over large geographic areas. Recently, for example, a multiprovince outbreak was identified in an Eastern Mediterranean community, and careful investigation and laboratory testing identified a rare form of Salmonella, likely due to contamination of a traditional food in this cultural group.⁴

Bottom line

Infections affect individuals but also spread through communities. Early detection and mitigation efforts are possible when there is effective synergy among primary care, public health, laboratories, and engaged communities. Practising this on the “small stuff” like gastroenteritis can help, not only to decrease morbidity in a community, but also to have this synergy in place for when more serious outbreaks occur.