DeMuri GP, et al. - The presence and density of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis were determined in the nasopharynx of 4–7-year-old children during upper respiratory tract infections (URTIs) and when well. During periods of both symptomatic and asymptomatic viral infection, the density and frequency of colonization with S. pneumoniae, H. influenzae, and M. catarrhalis in nasal wash samples increased. During asymptomatic viral infection, increases in bacterial colonization observed were nearly the same magnitude as when children were symptomatic.