"Prone to illness" is the term used to describe someone who is easily sick.
The origin of the phrase "prone to" comes from the Latin word "prōnus," meaning "leaning forward." In this context, "prone to" is used to describe a tendency or pkephood of something happening, such as being easily sick.
Examples:
She's always been prone to colds during the winter months.
He's prone to headaches after a long day at work.
Translations:
她冬天总是容易感冒。
他工作一天后常常头痛。