Classification	Key words	Extended words
Prevention stage	Flu vaccine	Flu vaccine side effects, Influenza vaccine necessary to fight it, Bird flu vaccine
Prevention stage	Flu prevention	How to prevent flu, Prevent influenza, Influenza outbreak, Prevent influenza A
Stage of symptoms	Cold	Gastro-intestinal flu, Influenza, Cold symptoms, Viral influenza
	Respiratory infection	Upper respiratory tract infection, Nasal congestion, Cough, Bronchitis, Sore throat, Runny nose, Rhinitis, Pharyngitis
	Fever	Fever, High fever, Headache, Dizziness, Fatigue, Fever, Chills
Treatment stage	Flu treatment	A stream of treatment, What medicine to eat flu
Treatment stage	Cold medicine	Baijiahei, Contac, Tylenol, Gankang, Amoxicillin, Cough, Antipyretics, Cephalosporins, Oseltamivir
Commonly used words	H1N1	H1N1 flu, H7N9, H7N9 flu
	Influenza-A	Influenza A, Type A H1N1 flu, Type A flu symptoms, What is Influenza A
	Influenza	Flu virus, Swine flu, Bird flu