Alien races can get diseases, but not like we have or can get.
They have had all their time, much longer than we have had, to figure out how to prevent and cure their diseases.
They also have the amount of moral motivation and the assistance of other races that we do not have.
I don't know about all diseases, but communicable diseases slow down when less people are communing.
That does not put an end or a cure to them though.
And many of our worst diseases are not communicable.
All people of all races can get diseases.
Advanced races have much less diseases and chance of getting them than we humans on Earth do.
Advanced races can cure much more than we can yet also.
Yes, all people of all races are affected by loss and death of family and friends.