How can an employer differentiate between heat-related illness and COVID-19 in high risk vulnerable worker populations?

Populations at risk for heat related illness include agricultural workers such as migrant farm workers (NCDHHS, 2019) and landscapers, municipal workers (McCarthy, 2019 ), such as police, firefighters and sanitation workers, miners, military personnel, construction workers, factory workers, and professional athletes. The signs and symptoms of heat-related illness (HRI) and COVID-19 illness may overlap. HRI is a continuum ranging from heat cramps or rash to heat exhaustion, which can lead to heat stroke and death. Symptoms include high body temperature, headache, dizziness, sweating, weakness, nausea, muscle pain among others (CDC, 2017, NIOSH, 2016). Among the symptoms associated with COVID-19 illness are cough, shortness of breath, fever, chills, muscle pain, headache sore throat, diarrhea, and new loss of taste or smell (CDC, 3/2020). There is overlap in many of these symptoms, including the more severe ones such as difficulty breathing, confusion and inability to arouse. There is also overlap between the preexisting conditions that render HRI and COVID-19 illness more severe (Calma 2020). These include lower socioeconomic status, advanced age, and chronic diseases such as hypertension, diabetes and obesity. An important distinguishing risk factor for COVID-19 is person to person transmission. HRI is most often related to work or physical activity in a hot environment, especially those who are not acclimatized or have pre-existing chronic conditions. Indeed, COVID-19 can coexist in such an employee, or present alone. Given these similarities, clinical differentiation may be difficult.. The environmental / occupational context in which these symptoms appear should be considered as it can help guide the proper diagnosis. 

Employers of workers at risk of HRI may find it useful to create a prevention plan to include strategies that minimize the risk for employee exposure to the virus, and that allow early detection of employees with symptoms of COVID-19 and/or HRI. Pre-shift employee temperatures and symptom screening questionnaires may allow for early identification of employees who may be ill and potentially need exclusion from work. This is advantageous as early medical care can reduce mortality in HRI (Stewart, 2011) and reduce person-to-person transmission of COVID-19 (CDC, 4/20). Workers should be educated about symptoms and prevention of HRI such as the importance of accessing adequate rest, water and shade, and of COVID-19 disease such as education about proper hand hygiene, social distancing, and respiratory etiquette / using a mask. Employers should ensure access to soap and water, hand sanitizer, disinfectant active against coronaviruses, and appropriate PPE. (CDC, 3/20; NCDHHS, 2019). Armed with the knowledge of a pre-shift temperature, risk assessment and ability to identify employees early will lead to prevention and early medical intervention if needed, as well as early initiation of contact tracing in the case of  COVID-19 illness. Assessing risk factors for HRI including recent work activity levels in the context of symptoms should provide useful information toward differentiation of these conditions.  Instituting proactive strategies in the workplace to prevent HRI should reduce the occurrence of illness and the need to differentiate it from COVID-19. Workplace heat stress awareness programs that include training, acclimatization and medical monitoring have been shown to be effective in reducing the frequency and severity of heat-related illness and are recommended by NIOSH (McCarthy, 2019, NIOSH, 2016).


McCarthy, RB, Shofer F, Green-McKenzie, J. Outcomes of a Heat Stress Awareness Program on Heat-Related Illness in Municipal Outdoor Workers, Journal of Occupational and Environmental Medicine: September 2019 - Volume 61 - Issue 9 - p 724-728 doi: 10.1097/JOM.0000000000001639

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Coronavirus Disease 2019 Situation Summary. CDC. Accessed on 4/4/2020 at: Apr 19, 2020
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Calma J. What happens when extreme heat collides with a pandemic?. Accessed on 5/3/2020 at:

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