The free Sickweather iOS app will provide you with real-time, geo-tagged alerts whenever you are about to enter a location in which a person has recently reported feeling ill.

“Choose from several illnesses, including Flu, Norovirus, Pink Eye and Whooping Cough,” the app’s creators explain.

“Sickweather uses a patent-pending process to track and map reports of illness … Reports are represented by blue “SICK” map markers — tap them for more information of exactly when they were reported. Some viruses can survive on surfaces for up to 48 hours and can have a viral life cycle of 2 weeks, so we color-code more recent reports as RED within 1 day, ORANGE within 2 days, YELLOW within 1 week, and we include reports as old as 2 weeks in BLUE.”

How exactly does it work? By constantly scanning social networks like Twitter and Facebook for indicators of illness (such as a person using the word “sick” in a certain context) — thereby allowing you to scour the horizon for potential winter colds with roughly the same accuracy you might look for clouds as a way of predicting rain.