The second issue in Bragdon was whether the patient's HIV infection posed a direct threat to others that would justify requiring her to have her dental work done in an operating room. Direct threat means a significant risk of substantial harm to the health or safety of others. The determination that an individual poses a "direct threat" shall be based on an individualized assessment of the individual's present ability to perform the essential functions of the job safely. 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 the following:

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.

Bragdon is the first U.S. Supreme Court decision on the meaning of "direct threat" under the ADA. Interesting, the only Supreme Court case to construe direct threat prior to Bragdon was also a disease control case: School Board of Nassau County v. Arline, 480 U.S. 273 (1987). Arline arose under the Rehabilitation Act and involved a teacher who was infected with tuberculosis and had periodic recurrences of the disease. The school district wanted to remove her from the classroom because it feared that the children would be infected. The teacher had an expert from the public health department who certified that she was not infectious at the time. The Court found that she did not pose a direct threat and could not be excluded from the workplace. However, the Court stated forcefully that if she became infectious to others, she would pose a direct threat and would have to be excluded from the workplace.

In Bragdon, the dentist refused to do dental work, including drilling, on an HIV-infected person in his office. The dentist claimed that he was concerned that he could not do adequate infection control in his office and offered to do the work at no extra charge at the hospital. (There was no discussion of whether there would be a charge by the hospital, but it is assumed there would be.) The patient refused and sued, alleging that the dentist violated the ADA. The dentist asserted the direct threat defense. He lost in the lower courts, but the U.S. Supreme Court ruled that he should be allowed to present evidence that HIV posed a threat to him or others unless he did the procedure at the hospital. This is an important precedent, although not necessarily the best facts. The case was remanded and the court of appeals found that the dentist had not made a sufficient showing of evidence of risk to justify his differential treatment of the patient.