expression, godan verb (-ru)
fall ill; get sick; contract a disease
Common expression for becoming ill or catching a disease. かかる is a godan verb; the phrase is often used in past tense (かかった) or with auxiliary verbs.
先週、風邪をひいて病気にかかった。
Last week I caught a cold and got sick.
彼は重い病気にかかって
He is suffering from a serious illness.