Real-time heat-related illness

The Centers for Disease Control and Prevention (CDC) defines surveillance as "the ongoing, systematic collection, analysis, and interpretation of health-related data essential to planning, implementation, and evaluation of public health practice, closely integrated with the timely dissemination of these data to those responsible for prevention and control." A syndrome is a group of signs (something a health care provider can observe, like a rash, or body temperature) and symptoms (something a patient feels - like pain, or fatigue) that are often associated with a particular disease or condition.

Heat syndrome is identified in surveillance data by looking for diagnostic codes for heat-related illness and by searching chief complaints (descriptions of why patients are at the ED) for words related to heat exposure and heat-related illness, such as overheating, sunstroke, and similar terms.

Syndrome data are inherently non-specific and are not based on diagnostic testing. While the NYC syndromic surveillance system captures data on 100% of ED visits in the city (as of 5/1/16), the data are not comprehensive because some residents seek care outside the city. These data are not exact measures and should be used to understand trends, rather than to count cases. In addition, recent data are not final and are subject to change. In addition, heat-related illness cases in syndromic surveillance data provide a useful indicator of the lethal impacts of extreme heat events, but the number of HRI cases does not reflect the full burden of health impacts, such as increases in death or hospital visits for heat-sensitive chronic conditions, which are not available in near-real time.

For more syndromes tracked by the Health Department, visit EpiQuery.

A heat syndrome is identified in surveillance data by looking for diagnostic codes for heat-related illness and by searching chief complaints (descriptions of why patients are at the ED) for words related to heat, such as overheating, sunstroke, and similar terms.

Syndromic data are inherently non-specific and are not based on diagnostic testing. They represent suspected rather than confirmed illness. While the NYC syndromic surveillance system captures data on 100% of ED visits in the city (as of 5/1/16), the data are not comprehensive because some residents seek care outside the city. These data are not exact measures and should be used to understand trends, rather than to count cases. Recent data are not final and are subject to change. In addition, heat-related illness cases in syndromic surveillance data provide a useful indicator of the lethal impacts of extreme heat events, but the number of HRI cases does not reflect the full burden of health impacts, such as increases in death or hospital visits for heat-sensitive chronic conditions, which are not available in near-real time.

For more information, see the Council of State and Territorial Epidemiologists' heat syndrome case definition.

Tracking heat-related illness (HRI) in near-real time can help provide situational awareness, supplementing the weather forecast as an indicator of public health risk. HRI detected in emergency department syndromic surveillance data are strongly associated with hot weather and highly correlated with daily counts of HRI hospital discharge data. However, HRI counts detected in the ED syndromic surveillance data represent suspected rather than confirmed illness, and are most useful to track trends. For example, some records may be counted as cases when they are not HRI, while other HRI cases may go undetected due to differences in hospital coding practices or because of what patients say when they describe what is bothering them.