to contract (a disease); incidence of becoming ill (term often used in medical or epidemiological contexts).
高齢者はインフルエンザに罹患すると重症化しやすい。
Elderly people are more likely to develop severe illness if they contract influenza.
その地域の罹患率が急増していると報告された。
It was reported that the incidence rate in that area is rising rapidly.
早期発見は罹患後の治療成績を大きく改善することがある。
Early detection can greatly improve treatment outcomes after contracting a disease.