Day 7: Thursday May 14, 2020

When clusters of enteric illness are identified, either within a single province/territory or across multiple provinces/territories, federal epidemiologists at the Public Health Agency of Canada (PHAC) are notified by PulseNet Canada via the Canadian Laboratory Surveillance Network (CLSN). Clusters of Salmonella are identified by PulseNet Canada using the following criteria: two or more isolates within 0-10 wgMLST allele differences. When a Salmonella cluster is identified based on this detection criteria, it is assigned a cluster code. More information on WGS and allele differences in an outbreak context is available here.

While reviewing PulseNet Canada’s weekly WGS cluster reports posted on CLSN, you notice that the Salmonella report includes a new single-jurisdictional cluster of five Salmonella Newport isolates from Ontario that are related by WGS. This cluster was assigned the following cluster code: 2005NEWWGS-1ON.

Cluster codes follow a standardized structure as outlined below.

 

 

 

 

Text description: A diagram illustrating the structure of a cluster code. Cluster code is 2005NEWWGS-1ON. Breaking down the structure of code is as follows: 20 (year); 05 (month); NEW (pathogen: Salmonella Newport); WGS (identified through whole genome sequencing) -1ON (first Ontario cluster of pathogen posted during month/year).

The first two numbers of a cluster code represent the year the cluster was first identified (e.g., 2020). The following two numbers represent the month the cluster was first identified (e.g., May, represented by 05). The next few letters in orange provide information about the pathogen and serotype (e.g., Salmonella Newport). The characters following the dash identify whether the cluster is single-jurisdictional (associated with one province or territory) or multi-jurisdictional (associated with multiple provinces or territories). If a cluster includes isolates from multiple provinces or territories, it is assigned an MP designation, which stands for multi-provincial. If a cluster is single-jurisdictional, it is assigned a designation to represent that jurisdiction (e.g., ON, which stands for Ontario).

As the cluster is single-jurisdictional, you know that PulseNet Canada did not identify any matches outside of Ontario. As all of the cases are currently within one province, Ontario will continue to take the lead on investigating these cases.

You decide to continue to monitor this cluster to see if any new isolates from another province or territory are added to this cluster in the coming weeks.          

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