The flu has passed epidemic rates in much of the country, and if you don't have a cold, I'm sure you have a friend who has the sniffles, fever, chills, aches and pains of a viral upper respiratory infection. This is different from a bacterial infection such as sinusitis, bronchitis, or pneumonia. A viral infection doesn't improve with antibiotics as these infections do. A virus hijacks your own body's healthy cells and uses it to reproduce and spread.