Long-COVID may have something to teach us. Those lingering symptoms of muscle pain, brain fog, and exhaustion are familiar to people who haven't had COVID -- but who suffer from chronic fatigue-- people who're often told "it's all in their heads." Like Dr. Michael Gallagher, of Denver. He was a triathlete -- contracted a common virus -- seemed to get better -- but wound up bedridden. Gallagher's new book "Run Down" is out today. We spoke in December.