. >> reporter: public health researchers john hanlin works for ecolab, a hygiene technology company. he says his team was hired by the majority of hotels and restaurants six months ago to ensure visitors stay healthy. so you teach your customers that they've got to be clean on these surfaces none stop. >> exactly. they've got to be cleaning them several times a day. but not only, that they've got to be using the right disinfectant. >> reporter: but the increased threat isn't just here in minneapolis. researchers have found cities that have teams in the super bowl, like boston and philadelphia, have an 18% increased risk of flu-related death for people over 64. >> you have more chance... epidemiologist mike osterholm also says fans are upping their odds of contracting the flu if they do go to the game. >> think of influenza almost leak a lottery. so if in a normal day you only come in contact with 10 people, that's one chance. if you come in contact with 100 or 1,000, you just upped your chances that much more. >> reporter: and the super bowl isn't just about the 65,000 people attendi