Yes. The ADA permits employers to exclude individuals who pose a direct threat -- i.e., a significant risk of substantial harm -- to the health or safety of the individual or of others, if that risk cannot be eliminated or reduced below the level of a "direct threat" by reasonable accommodation.
However, an employer may not simply assume that a threat exists. ; the employer must establish through objective, medically supportable methods that there is The determination that an individual poses a significant risk of substantial harm must be based on an individualized assessment of the individual's current ability, based on the most current medical knowledge and/or on the best available objective evidence.
By requiring employers to make individualized judgments based on reliable medical or other objective evidence rather than on generalizations, ignorance, fear, patronizing attitudes, or stereotypes, the ADA recognizes the need to balance the interests of people with disabilities against the legitimate interests of employers in maintaining a safe workplace.
For additional information, take a look at the following resource:
FAQ: Does the ADA require that an applicant or employee with a disability be qualified for the position?