A Japan-based sailor died following a physical fitness test in May, at least the third such death in the Navy this year.

Aviation Electrician Airman Jordan C. Cook, 22, “exhibited symptoms of illness” on May 1 following his physical readiness test, or PRT, according to Naval Forces Japan spokesman Cmdr. Reann Mommsen.

He was initially taken to a clinic on Marine Corps Air Station Iwakuni and later to an off-base hospital, where he died on May 2, Mommsen said.

Mommsen did not provide further details on the Georgia native’s passing.

“The cause of the death is currently under investigation pending the results of an autopsy,” she said in an email.

Cook was stationed in Japan with the Diamondbacks of Strike Fighter Squadron 102, his first duty station out of school.

Cook’s passing follows the deaths of two Navy recruits at the sea service’s Great Lakes boot camp this year.

Seaman Recruit Kelsey Nobles, 18, collapsed following her PRT and later died on April 23.

On Feb. 22, Seaman Recruit Kierra Evans, 20, also collapsed following her PRT and died.

Such deaths remain relatively rare, with the Naval Safety Center reporting 17 physical training fatalities over the past decade.

Roughly a week after Cook’s death, Navy officials announced “universal training precautions” for the fleet “to reduce the risk of exercise-related collapse and death during physical exercise,” according to a press release pointing sailors to a new naval administrative message, or NAVADMIN.

“The NAVADMIN was released to reinforce universal preventive measures, raise awareness of common pre-existing conditions affecting our service members, and describe the early signs of distress that can signal a need to terminate training,” Lt. j.g. Stuart Phillips, a spokesman for the Chief of Naval Personnel, said in an email last month.

It calls on command fitness leaders to foster a culture that recognizes the early signs of distress during exercise.

“All personnel present during a training evolution or PRT can encourage good performance but should be on guard for signs that a participant is struggling and be ready to terminate the evolution,” the release states.

The PRT is supposed to measure overall health and wellness and is not a measure of “individual athletic prowess,” the release states.

“No one should risk their life by pushing through life-threatening conditions during a PRT,” it added.

The release indicated that personal risk factors for exercise-related collapse include underlying cardiac conditions and those who have inherited at least one sickle cell gene and thus have sickle cell trait.

“If you don’t know if you have (sickle cell trait), find out,” the Navy release states.

Sickle cell trait disproportionately affects African-Americans, and some people with the trait have been shown to be more likely “to experience heat stroke and muscle breakdown when doing intense exercise,” according to the U.S. Centers for Disease Control and Prevention.

The CDC notes that more research is needed to find out why some people with the trait have complications while others do not.

Commanders should allow any sailors showing distress to retake the PRT once they are medically cleared to do so, Navy officials say.