Dear Dr. Roach: Why is there a flu season instead of it being a year-round health challenge? And why do flu strains originate in Southeast Asia instead of, say, Poughkeepsie, New York? M.S.
Answer: Why there is a flu season is a bit of a mystery. Scientists used to think it was due to people staying indoors more during cold weather or because vitamin D levels are low. But research from tropical countries suggests that it has more to do with the combination of temperature and humidity that is optimal for influenza virus transmission, which likes cooler and drier…
