Originally Posted by MrPinks

He's been quarantined for a virus he might have. One they became in contact with him, the people stranded on the island might end up with the same virus. The reason no one is rescuing them is because the whole island is possibly quarantined and they know that if the plane crashed there and if the survivors are rescued then can spread the virus to the entire world.

Plus, Walt has the ability to make things a reality just by envisioning it psychically.