My son has just gotten over a case of the flu with a mild fever and coughing and congestion. Yesterday he was active, but today he can barely walk. The back of his calves hurt him and he can only get around by crawling on all fours. He s in good spirits except for the pain when he tries to stand. He is 7 years old and has always been a healthy boy. He has gotten a few infections since entering school as a kindergartener.