This is the 9584th most frequent Japanese word.
罹患
"罹患" means "to contract or be afflicted by a disease."
The word '罹患' here means 'contracted (a disease)' and is used explicitly to indicate that the person has been affected by that disease physically.
彼はその病気に罹患してしまった。
He contracted that disease.
In this statement, '罹患率' refers to 'prevalence rate', indicating the statistical increase of diseases affecting populations.
最近、罹患率が上昇している病気が多い。
Recently, there are many diseases whose prevalence rates are increasing.
Here, '罹患' implies the act of contracting diseases, highlighting preventive measures against it.