Symptoms include physical, cognitive, emotional, neurological, occupational, and/or role-playing problems that may be caused by post-viral fatigue syndrome. The severity of these impairments might vary, and they can also evolve over time. Several terms, such as myalgic encephalomyelitis (ME), post-infectious fatigue syndrome (PIFS), chronic fatigue syndrome (CFS) , Iceland disease, systemic exertion intolerance disease (SEID) and Royal Free disease, can be used interchangeably by healthcare providers to refer to post-viral fatigue syndrome. It is depending on severity and duration that these diagnoses alter. While CFS's specific etiology remains a mystery, post-viral fatigue syndrome is widely considered to be caused by either an acute or persistent viral infection.