Phrase guide

index case

noun · 2 senses · updated from the 2026-07-25 local source snapshot

Definitions and examples are grouped by meaning. Pronunciation, history, word forms, translations, descendants, synonyms, antonyms, derived terms, and related words appear whenever the source provides them.

Sound

Pronunciation

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No pronunciation record was provided for this word.

1

noun

Meaning 1

The first documented case in a disease epidemic within a population or the first case of interest in an epidemiological investigation: the case of patient zero (the index patient).

Definition source: English Wiktionary via Wiktextract

Topics: epidemiology, medicine, sciences

No example sentence was provided for this meaning.

Meaning relationships

Synonyms: none provided

Antonyms: none provided

Broader terms: case

2

noun

Meaning 2

the earliest documented case of a disease that is included in an epidemiological study

Definition source: Princeton WordNet 3.0

No example sentence was provided for this meaning.

Meaning relationships

Synonyms: none provided

Antonyms: none provided

Broader terms: patient

History

Etymology

No etymology was provided for this word.

Across languages

Translations

13 source translations are retained for this English entry.

  • Catalan: cas índex — first documented patient in a disease epidemic
  • Catalan: pacient zero — first documented patient in a disease epidemic
  • Finnish: indeksitapaus — first documented patient in a disease epidemic
  • French: patient zéro — first documented patient in a disease epidemic
  • German: Indexpatient — first documented patient in a disease epidemic
  • Italian: caso indice — first documented patient in a disease epidemic
  • Italian: paziente zero — first documented patient in a disease epidemic
  • Polish: przypadek wskazujący — first documented patient in a disease epidemic
  • Portuguese: caso índice — first documented patient in a disease epidemic
  • Portuguese: paciente zero — first documented patient in a disease epidemic
  • Russian: нулевой пациент (nulevoj pacijent) — first documented patient in a disease epidemic
  • Spanish: caso índice — first documented patient in a disease epidemic
  • Spanish: paciente cero — first documented patient in a disease epidemic