Direct threat means a significant risk of substantial harm to the health or safety of the individual or others that cannot be eliminated or reduced by reasonable accommodation. The determination that an individual with a disability poses a direct threat shall be based on an individualized assessment of the individual's present ability to perform safely the essential functions of the job. This assessment shall be based on a reasonable medical judgment that relies on the most current medical knowledge and/or on the best available objective evidence. In determining whether an individual would pose a direct threat, the factors to be considered include:
(1) The duration of the risk;
(2) The nature and severity of the potential harm;
(3) The likelihood that the potential harm will occur; and
(4) The imminence of the potential harm.