The pilot episode of The Walking Dead saw Rick Grimes waking up from a coma in a deserted hospital, but how he survived that long with the outbreak still going on around him and how long he was in a coma remained a mystery. A flashback in the first season revealed that Shane had left Rick behind as chaos erupted in the hospital. Rick came out of his coma about a month later, with an IV in his arm indicating that someone was checking on him regularly. Though surviving that long without food and water is unlikely, the liquid from the IV bag would have sustained him temporarily.