Simply replace the unfilled areas such as "[]" and "[date]" with your information.
Dear [name],
I am sorry to hear that you are not feeling well. I hope you are not feeling uneasy or uncomfortable. Please do not hesitate to let me know if there is anything I can do for you, [name]. I would be more than happy to be of any help during this time.
My thoughts are with you, hopefully you will soon be back on your feet.
Best regards,