What Causes Sore Muscles, Body Chills Along With Cold?

My wife has suffered with flu like symptoms, achy muscles, sore neck, arms, body acks all over, chills and states that she is cold from the inside. Taking a warm to hot bath will warm her up for a few hours. She has seen to two separate specialists in Canada and they are stumped. The one specialist feels she caught a bug while she worked in Mumbai India in 2008 and when she gets run down the bug resurfaces. They have been unable to locate the bug through blood tests etc. What can you suggest?