Viral infections of the respiratory tract are common events in all age groups and are the leading cause of mortality in children under 5 years of age in developing countries [1]. These infections cause significant economic burden, with estimated direct and indirect medical costs in the US exceeding $70 billion annually [2, 3]. Children under the age of 5 have an average incidence rate of four to six viral respiratory infections/year and the rate gradually decreases to one to two/year in most adults [4].