Surveillance of Heat-Related Illness Among Pinal County Residents in Arizona

Primary Topic Areas: 
Public Health Problem (100 words): 

Extreme heat events caused by high environmental temperatures are considered a major cause of weather-related deaths and injury in the United States. These events can result in a spectrum of conditions known as heat-related illnesses (HRIs), which range from minor to life threating symptoms. In Arizona, HRIs account for more than 2,000 emergency room visits and 118 deaths each year. In 2012, there were a total of 1,572 emergency department visits related to HRIs. Pinal County Public Health Services District (PHSD) sought to gain a better understanding of the scope of HRI among Pinal County residents.

Success Story Narrative (400 words): 

Pinal County Public Health Services District, along with the help of Arizona Department of Health Services, Arizona State University, and the University of Arizona, aimed to improve the surveillance of heat-related illness in Pinal County. Normally, PHSD uses the National Syndromic Surveillance Program’s (NSSP) BioSense Platform to investigate HRI in the county using ICD-9 and ICD-10 codes related to environmental heat-related illness. However, with recent funding from a sub-grantee award from the CDC, PHSD wanted to obtain a better understanding of the scope of heat-related illness and vulnerable populations in Pinal County.  

In 2017, PHSD went further into their investigation of HRI among Pinal County residents by using a combination of hospital discharge data (HDD), the ESSENCE syndromic surveillance tool within the BioSense Platform, and a survey. Hospital visits related to HRI prior to 2017 were investigated using hospital discharge data from 2010-2016. Again, identifying HRI hospital visits was done using ICD-9 and ICD-10 codes. For the summer of 2017, ESSENCE was used to detect HRI visits between May 1st and September 12th. Detection of HRI visits in ESSENCE was performed using ICD-10 codes and chief complaint text related to environmentally induced HRI that the Council of State and Territorial Epidemiologists recommends in their 2016 HRI syndrome query guidance document: Individuals detected for visiting a hospital for heat-related illnesses in ESSENCE were contacted to participate in a questionnaire developed by PHSD. The questionnaire was developed prior to the start of the 2017 summer investigation, and included questions related to the nature and location of the HRI incident, potential risk factors, and knowledge and awareness of HRI. Interviews were approved and conducted with coordination of Pinal County’s infectious disease and epidemiology team that routinely conducts interviews to improve public health in the county.

Outcomes And Impact (400 words): 

Although surveillance of heat-related illness in Pinal County has recently become an area of focus for Pinal County Public Health Services District, previous surveillance of HRI conducted for the summer of 2016 indicated that occupations might be related to the HRI incidents among Pinal County residents. Data from HDD, ESSENCE, and the interviews analyzed in 2017 helped support this observation. Hospital discharge data and ESSENCE syndromic surveillance data suggested HRI hospital visits are more likely to occur in males between the ages of 20-44 years old. Analyzing the interview data suggested that this might be because these individuals are working in occupations that expose workers to extreme heat.

During the project conducted in 2017, PHSD was also able to identify trends in HRI in Pinal County. The department discovered spikes in HRI hospital visits around the end of June each year which typically coincided with the first National Weather Service Extreme Heat Warning of the season. When conducting the interviews, the response rate obtained was better than what was expected at the beginning of the project. Overall, the responses from the interviews were able to give some context to why some of these heat-related illness incidents are occurring, which was lacking in previous years of HRI surveillance.

With funding from the sub-grantee award from the CDC, Pinal County Public Health Services District plans to continue using ESSENCE to investigate HRI, and conduct interviews on individuals identified for seeking treatment at a hospital for HRI. PHSD is also using the information obtained from their activities to collaborate with local organizations and stakeholders in Pinal County in order to develop strategies to respond to extreme heat. Some of the local organizations and stakeholders working on responding to HRI in the county have already found the information obtained in 2017 to be useful in their efforts.

Lessons Learned (400 words): 

Syndromic surveillance data are useful for understanding the scope and demographics of heat-related illnesses in almost real-time for the incidents. Syndromic surveillance data can detect individuals seeking medical treatment for a possible heat-related illness incident before a confirmation for HRI occurs. Without the BioSense Platform, Pinal County Public Health Services District would need to wait for hospital discharge data to obtain information on HRI incidents in Pinal County.

Interviews are an informative approach for understanding the underlying circumstances of HRI. Data provided by interviews provide information that hospital discharge data and ESSENCE lack. Information obtained by interviews can also be used to validate information obtained from hospital discharge data and ESSENCE.

Combining hospital discharge data, syndromic surveillance data, and interview data can provide information that organizations and stake holders can use to prepare for extreme heat in the future. This methodology can help with making informed decisions on how to respond to HRI each summer when the frequency of heat-related illnesses increases.

For other public health organizations interested in conducting interviews for HRI surveillance, it is recommended to coordinate with your local institutional review board and/or resources to determine if an IRB approval is needed to conduct the interviews.

Submitting Author Name: 
Dylan Kent
Submitting Author Title: 
Epidemiology Intern
Submitting Author Organization: 
Pinal County Public Health Services District
Submitting Author Email:

May 08, 2018

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