Peace be upon you. If the illness persists until the next Ramadan and the person is unable to make up the fast, they must pay fidya, which is to feed one poor person with a measure (750 grams) of food for each day of fasting missed. This fidya can only be paid when the next Ramadan arrives. It is not sufficient to give the monetary value of the fidya to the poor instead of the food itself; however, you may give the equivalent amount to the poor if you are certain that they will use it to buy the specified food on your behalf for the fidya. According to Ayatollah Khamenei, the fidya must be paid in kind (food), and the same ruling applies to expiations. According to Ayatollah Sistani, the fidya must also be in the form of food, and the monetary value is not acceptable. May you be successful in all good deeds.