If it's just a cold, go. But if you have the flu, which can make people very sick, and it's within the first 5 days, you owe it to yourself and everyone on the plane (if applicable) and at the interview, to not spread it to them. Call your doctor and see how long it will take to get flu results. If you can get back results before you leave, get tested. If you won't get the results in time, explain to the doc your circumstances. If he or she thinks it's the flu, I'm going to guess they'd advise you not to go if you are in the infectious stage. If you went and the admissions team knew that you possibly spread the flu, or something similar, they could a) think you're really dedicated or b) think you're really stupid and out to lunch when it comes to public health.