Update: Heat illness, active component, U.S. Armed Forces, 2017.

In 2020, there were 475 incident cases of heat stroke and 1,667 incident cases of heat exhaustion among active component service members. The overall crude incidence rates of heat stroke and heat exhaustion were 0.36 cases and 1.26 cases per 1,000 person-years; both were the lowest annual rates in the 2016-2020 surveillance period. In 2020, subgroup-specific rates of both incident heat stroke and heat exhaustion were highest among males, those less than 20 years old, Asian/Pacific Islanders, Marine Corps and Army members, recruit trainees, and those in combat-specific occupations. During 2016- 2020, a total of 341 heat illnesses were documented among service members in Iraq and Afghanistan; 7.0% (n=24) were diagnosed as heat stroke. Commanders, small unit leaders, training cadre, and supporting medical personnel must ensure that the military members whom they supervise and support are informed about the risks, preventive countermeasures, early signs and symptoms, and first-responder actions related to heat illnesses.