Influenza refers to many strains of viral illness that are more intense than a common cold, and typically include fever, muscle aching, headache, and fatigue. Some kinds of flu have cold-like symptoms with sore throat or respiratory involvement; others focus on the digestive tract, with diarrhea, nausea, or vomiting. If a strain of flu with a characteristic set of symptoms is ‘going around,’ a remedy that matches them can often be used preventively. When a person is ill, a remedy should be chosen to match the specific symptoms.