index patient

American  

[in-deks pey-shuhnt] / ˈɪn dɛks ˌpeɪ ʃənt /

noun

Pathology.

1. 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.

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Etymology

Origin of index patient

First recorded in 1950–55

Example Sentences

Investigators suspected cases were driven in part by the apartment’s sanitary system, because the outbreak seemed to begin after an index patient suffering from diarrhea used a toilet in the apartment complex.

From Washington Post • Jun. 16, 2020

The Ministry of Health also asked people to contact a hotline if they had been at the hospital in the 2 weeks after the index patient was admitted.

From Science Magazine • Jun. 5, 2015

That man became Nigeria's first Ebola case—the index patient.

From Scientific American • Oct. 18, 2014

The virus spread from that one index patient to 318 people, resulting in 280 deaths.

From Nature • Oct. 8, 2014

Without knowing the index patient, investigators can’t know how the fateful spillover happened.

From New York Times • Apr. 9, 2014