As per the wiki:

Viral status amplifies damage to the health of the afflicted target by 100% for 6 seconds. Subsequent procs add 25% increased damage to health up to 325% in total after 10 stacks, with each proc having their own duration.

Once the [Cryotra] hits an enemy it quickly gets a 10x viral proc status in addition to a radiation proc which is helpful for crowd control.

Personally this has replaced my use of Vigilante or Gladiator mods as stat sticks (with a few exceptions like stealth frames) since the effect of the [Cryotra] affects melee, primary and secondary weapons, not too mention warframe abilities to inflict damage.