Symptoms of ME/CFS may progress or deteriorate over time. A person with ME/CFS may be in a certain stage of their illness right now, but their condition might improve or worsen over time. Some individuals' condition might progress dramatically for no apparent reason. Other people suffer from a "fluctuating sickness," which may endure for months or even years. The reason behind this is unknown. ME/CFS is a chronic illness for the vast majority of sufferers. Fewer than 10% of patients achieve full recovery (returning to pre-injury functionality). When the condition progresses, some ME/CFS sufferers may discover that they are able to perform more as time goes on. It's important to note that this isn't always the case.