While travel hubs in most cities are more hygienic than in [Mary Ramsey]'s day, Dr Ronald Cutler, an expert in infection control at Queen Mary University of London, says the frequency of travel has affected the potential for disease to spread. "In the past," he says, "if you were going on a boat to the Americas it might take six or seven weeks to g...

G2: Health: Going viral: Parasites rampage through crowded populations, so is urban life bad for our health? Kira Cochrane finds out how cities deal with infectious disease