Strange storm cloud in Worms Reloaded

I did an online match and happened that my opponent used a strange storm cloud on one of my worms.

This cloud remained some turns on the head of my worm and then disappeared, but I didn't really understood what was its effect.

Can you explain?

Marked For Death is a new weapon introduced in Worms Reloaded. It is activated by placing the cursor over the target worm, then using it. The afflicted worm will be marked with a storm cloud over their head and they will take highly increased damage until their death.

Source: http://worms.wikia.com/wiki/Marked_For_Death

Edit: All attacks do double damage for the rest of the game.