“久病衰弱”可以翻译为 “weakened by prolonged illness” 或 “debilitated from a long-term illness”。
“weakened by prolonged illness” 侧重于表达因长期患病而身体变得虚弱。
“debilitated from a long-term illness” 中，“debilitated”意思是“使衰弱、使虚弱”，“from a long-term illness” 表明是由于长期疾病，整体也清晰传达了“久病衰弱”的含义 。