The invention relates to a thermal-treatment vessel (17) for pathogenic liquids intended for being filled to a predetermined level leaving a compression dome, characterised by comprising at least one pressurised-steam injector (31) positioned such as to be submerged in the liquid contaminated by pathogenic agents when the thermal-treatment vessel (17) is filled to the predetermined level with the liquid contaminated with pathogenic agents and directed toward the inside of the thermal-treatment vessel (17) with at least one tangential component so as to create a cyclonic movement of the liquid contaminated with pathogenic agents to be decontaminated.