sickly person; invalid
Refers to a person who is chronically ill, frail, or in poor health. The term is somewhat formal and may appear in medical or social welfare contexts.
Sickly people are susceptible to infectious diseases.
This facility provides special care for invalids.
虚弱者 also means a physically weak person, but 病弱者 specifically implies illness as the cause of weakness.
Compound of 病 (byō, 'illness'), 弱 (jaku, 'weak'), and 者 (sha, 'person'). The term is a straightforward Sino-Japanese construction.