Characterizing the Effects of Extreme Cold Using Real-time Syndromic Surveillance, Ontario, Canada, 2010-2016.

Morbidity and mortality from exposure to extreme cold highlight the need for meaningful temperature thresholds to activate public health alerts. We analyzed emergency department (ED) records for cold temperature-related visits collected by the Acute Care Enhanced Surveillance system-a syndromic surveillance system that captures data on ED visits from hospitals in Ontario-for geographic trends related to ambient winter temperature. We used 3 Early Aberration Reporting System algorithms of increasing sensitivity-C1, C2, and C3-to determine the temperature at which anomalous counts of cold temperature-related ED visits occurred in northern and southern Ontario from 2010 to 2016. The C2 algorithm was the most sensitive detection method. Results showed lower threshold temperatures for Acute Care Enhanced Surveillance alerts in northern Ontario than in southern Ontario. Public health alerts for cold temperature warnings that are based on cold temperature-related ED visit counts and ambient temperature may improve the accuracy of public warnings about cold temperature risks.