"Protect their lives" 
I didn't know so many sailors were elderly with underlying serious health conditions....
Young people seldom die or corona, but can end up with irreversible lung damage (the chinese virus causes chronic pneumonia, severely infected lungs)
Anyone who smokes, or has any lung problem (astma, bronchitis etc), is extra vulnerable
And: obese people make up 90% of intensive care patients in some hospitals in The Netherlands. As many Americans are obese, this can also be a problem in law enforcement, or in the armed forces