Several members of the Kira Task force (that Light was in charge of), as well as Near's team, were present during the climax where
Light is exposed as Kira by Teru Mikami when Light's name is the only one not written in the Death Note.
The task force knew about Death Notes since
Ren gave it to Kyosuke Higuchi and the task for caught him in possession of it
Which is revealed much earlier in the story.
Near realized Kira would likely use a catspaw to throw suspicion from himself so simply finding the person in physical possession of a Death Note wasn't enough. He had to make sure he found the Death Note, and make Kira believe he'd won so he would show himself.
Replaced the pages of the Death Note held by Teru Mikami (though Light was still the owner), and allowed Light to lure everyone to the creepy abandoned warehouse where Teru Mikami called Light "God" and wrote the names of everyone present, except Light. Proving Light was actually Kira.
With Kira's real identity exposed, there was no reason to go hunting for other Kiras or other Death Notes - they had found the root cause.
Depending on if it's the manga/movies/anime Misa
Kills herself, or it's heavily implied she does.
As for the task force, my guess is they continued working as an anti-Kira taskforce in some capacity, at least in the manga, because
The manga ends with a group of Kira's followers praying for his return.
Youtube link to the end with several characters