The clinical presentation is a diagnosis of exclusion that includes respiratory symptoms (eg, cough, chest pain, shortness of breath), gastrointestinal symptoms (eg, abdominal pain, nausea, vomiting, diarrhea), nonspecific constitutional symptoms (eg, fever, chills, weight loss), reduced blood oxygen levels, elevated white blood cell counts, and injuries resembling those caused by exposures to toxic chemical fumes, poisonous gases, and toxic agents.