Gulf War syndrome or Gulf War illness is a chronic and multi-symptomatic disorder affecting returning military veterans of the 1990–1991 Persian Gulf War. A wide range of acute and chronic symptoms have been linked to it, including fatigue, muscle pain, cognitive problems, insomnia, rashes and diarrhea. Approximately 250,000 of the 697,000 U.S. veterans who served in the 1991 Gulf War are afflicted with enduring chronic multi-symptom illness, a condition with serious consequences.