Are you sure it was a cold? To me it just sounds like a bad case of 'standard ME symptoms'! People with ME often think they are getting frequent colds and flu because that's what the symptoms are like. But that is also what ME symptoms are like! As Jonathan Edwards said, symptoms of infection are mostly due to our immune reactions. And the symptoms of ME are also largely due to persistent (auto)immune activity, at least in a significant subset. In my experience, such worsenings occur after over-exertion and/or excessive carbohydrate consumption.