What can be the results to the human health if fire in the chernobyl area cannot be stopped? how quick the radiation spreads to the neighbour countries and to the world? what measures can be taken? nuclear masks?

Serenity: I am not worried about this at all. The radiation increase was probably burning of radioactive vegetation and old fallout getting circulated in the smoke. This is temporary and mild. The reactor is encased in concrete, it will not burn. Just for your educational enjoyment: potassium iodide taken in very small doses can decrease the effects of radiation on the body. Do not use it right now.