infection has 2 distinct synonyms spread across 2 of its 7 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. WordNet records no antonym for it — antonymy is a relation between word forms rather than concepts, so it is deliberately sparse.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
the pathological state resulting from the invasion of the body by pathogenic microorganisms
(phonetics) the alteration of a speech sound under the influence of a neighboring sound
(medicine) the invasion of the body by pathogenic microorganisms and their multiplication which can lead to tissue damage and disease
an incident in which an infectious disease is transmitted
the communication of an attitude or emotional state among a number of people
“a contagion of mirth”
moral corruption or contamination
“ambitious men are led astray by an infection that is almost unavoidable”
(international law) illegality that taints or contaminates a ship or cargo rendering it liable to seizure
Synonyms, antonyms and the broader and narrower relations for infection come from Princeton University’s WordNet. Full sources and licences.