The investigators conducted a pilot study from the fall of 2007 until October of 2009, looking at FeNO levels in RSV infected patients and compared it to non-RSV viral infections. The investigators recruited a total of 28 RSV positive and 1 RSV negative subjects, as well as 4 control subjects. The investigators found FeNO values not statistically significant between the study group (the two-tailed p=0.09, considered not quite significant), but there was a trend of higher FeNO values in the non-RSV group when compared to the RSV group. A larger sample may detect a statistically significance between these 2 groups.