A B757 First Officer reported sighting a weather balloon at 7;500 FT; requiring evasive action by the Captain to avoid it.

Narrative

Climbing through 7;500 FT; cleared to 16;000 FT and direct to MNATE; we spotted what appeared to be a balloon that we were on a collision course with. The Captain; [as] pilot flying; disconnected the autopilot and stopped the climb; narrowly avoiding the balloon. As it went by my window; I noticed that it was a weather balloon with a telemetry package deployed underneath. We immediately advised ATC and received clearance to continue climb and route to MNATE. Center was unaware there was balloon activity in the area and then advised the aircraft following our routing. The balloon was coming basically from approximately 190/200 degrees and tracking north/northeast. Center could not have known of the threat and the Captain did an excellent job of avoiding the craft. He proceeded to call the flight attendants and explained the situation that just happened and asked if anyone was injured as we had allowed the flight attendants up as we approached VKZ. There were thunder cells in the area; but the area we were flying in was clear enough that we saw the balloon.