Viral respiratory tract infections such as influenza, H1N1 flu and swine flu are contagious. Contracting any infection depends upon your immunity of body. If your immune system is weak then you can contract any infection even with minor and social exposure with patients. But if your immunity is strong then there is very little chance of contracting infections. Systemic bacterial and fungal infections are usually non-contagious with few exceptions such as diphtheria and whooping cough which might be contagious. Upper respiratory tract infections are usually caused by influenza virus to which we have already exposed during childhood. So we are mostly immune to such infections. Advice 1. Take high protein diet such as cheese, pulses, eggs, and meat to boost immunity 2. Wear face mask whenever you are exposed to patients with H1N1 flu and swine flu 3. Workout in gym at least ½ an hour in a day for 5 days in a week – it boost immunity 4. Eat fruits and vegetables I hope this information will help you. I will be happy if you ask another question Thanks for asking question Thanks