In the still living category it breaks down thusly:
Season 1
-Gene Barry
Lee Grant
Robert Culp
Susan Clark
(4 of 9. Eddie Albert passed away in the last year)
Season 2
-Culp
Honor Blackman
Leonard Nimoy
Martin Landau
(3 of 9 from 8 episodes)
Season 3
-Culp
Vera Miles
Jackie Cooper
(3 of 8)
Season 4
-Robert Conrad
Dick Van ****
Patrick McGoohan
Robert Vaughn
(5 of 6)
Season 5
-McGoohan
Hector Elizondo
Ricardo Montalban
(3 of 6. Fred Draper died in 1999)
Season 6
-William Shatner
Joyce Van Patten
Theodore Bikel
(3 of 3)
Season 7
-Trish Van Devere
Louis Jourdan
Nicol Williamson
Clive Revill
(4 of 5)
So that means 25 of 46 Columbo killers are still alive. The first to die incidentally, was Laurence Harvey, who died just eight months after he made his Columbo appearance in 1973.