当留学生生病时，可以通过以下几种方式表达感谢：

直接表达感激之情

可以对帮助你的人说：“谢谢你在我生病期间给予我的关心和照顾。”

写一封感谢信

编写一封感谢信，详细描述对方在生病期间提供的帮助和支持，并表达你的感激之情。

保持联系

在病愈后，通过电话、短信或社交媒体等方式与帮助你的人保持联系，让他们知道你依然感激他们的关心和支持。

请客吃饭

在病情好转后，可以邀请对方一起共进晚餐，以表达你的感激和关心。

回赠礼物

在身体恢复后，可以送给对方一份心意礼物，以表达你的谢意。

当面致谢

在合适的场合，当面向提供帮助的人表示感谢，让他们知道你非常珍惜他们的关心。

Dear [Name],

I hope this letter finds you in good health. I wanted to take a moment to express my deepest gratitude for your kindness and support during my illness. Your selfless actions and concern made a significant difference in my recovery, and I am truly thankful.

During my time in the hospital, your visits brought me a lot of comfort and warmth. It was heartwarming to know that someone was thinking of me and taking the time to come and see me. Your presence meant a lot to me, and I am deeply grateful for your help.

I am now back home and on the mend. I will always remember your kindness and will do my best to repay your generosity. If there is ever anything I can do for you, please do not hesitate to ask.

Once again, thank you from the bottom of my heart. I wish you all the best and hope to see you soon.

Sincerely,

[Your Name]