The Cruz Roja said Thursday that 30 persons have been treated after they had run-ins with bulls.
These are the so-called toreros improvidados or amateur bull fighters who get in the ring with a fighting animal.
The Cruz Roja said that 12 persons had to be hospitalized, but that number also included some of about 66 who were injured or became ill while visiting the carnival.
Bulls have short attention spans, and the mass of individuals in the ring generally distracts the animal. But even once in awhile, a bull zeros in on someone who has been antagonizing him and runs him down.
So far no deaths have been reported, but such tragedies are not unknown in the Costa Rican version of bull fighting, or more correctly bull baiting.
The operators of the rondel at the Zapote fairground charges admission for spectators to watch the antics with the bulls. Some of the toreros improvidados dress in elaborate costumes. One Christmas day had on a Batman costume. Some wear capes as a way of distracting the bull.
The rondel also hosts traditional bull riding in which participants try to stay on the animal, which is trained to cast them off.