patient zero From WikiWord, the free dictionary English Contents DefinitionsRelated wordsReferences DefinitionsnounThe initial patient in the population of an epidemiological investigation. Related wordsSynonymsindex caseindex patientprimoinfectionprevalencepatient under investigationincubation periodpropositusprimaryground zeroendpointpropositapreobservationpre-oppreinfectionprior probabilityonsetzeroth grade References Wiktionary — patient zero Wikipedia — patient zero