Any time someone goes spear fishing , there is a chance of attracting a shark. The best prevention is to get the fish out of the water soon as you shoot it. While diving in clear water, the sharks see a diver realizing that it is not a helpless fish and will avoid going after you. In low visibility the sharks tune into the sound, the thrashing noise that a swimmer, snorkeler and or diver will make. This sound is like that of a fish in distress luring in the predator.
Bottom line is that there is no more of a problem as any other time.
Every year at this time the sharks migrate, every year the media hype it up because they have nothing else to talk about. Also, the areas where people have been hit, there is more to the story than what they tell. The boy who got hit and lost his arm, his uncle was fishing for the shark and the kids went in the water when the uncle brought the shark in closer. As with a lot of animal attacks, it is defensive, not offensive. I am not saying that you should not take precautions, always be orientated to your new dive location.