When anthrax becomes airborne, it can cause a deadly illness called inhalation anthrax.

The warning came as a New Jersey postal worker was confirmed to have inhalation anthrax, the deadliest form of the disease.

The U.S. Food and Drug Administration granted the designation to cethromycin for the prophylactic treatment of patients exposed to inhalation anthrax.

This was tested in two animal models of inhalation anthrax, rabbits and guinea pigs infected by intranasal instillation of Vollum spores.

An investigation into how a New York hospital worker died from a mystery case of inhalation anthrax was today being stepped up.