the first person known to have a particular disease or other medical condition in a population, especially the first patient in an epidemic known to have contracted the infection: The index patient did not immediately test positive, and consequently spread the virus for several days.
- Also called in·dex case pa·tient [in-deks keys pey-shuhnt] /ˈɪn dɛks ˌkeɪs ˌpeɪ ʃənt/ .
- See also patient zero (def. 1).
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023