Respiratory syncytial virus infections in infants: quantitation and duration of shedding.

Infants hospitalized with respiratory syncytial virus infection were studied to delineate the quantitative shedding patterns and duration of shedding of RSV. Nasal wash specimens collected daily from 19 infants contained a mean maximal titer of 4.34 log10 50% tissue culture infective doses per milliliter. On admission, the mean titer was 4.14 log10 TCID50, with no consistent decline until after Day 6. The mean duration of shedding for 23 patients until they were virus negative was 6.7 days with a range of 1 to 21 days. Quantities of RSV shed were significantly greater in infants less than one month of age and in infants with evidence of pulmonary consolidation on chest roentgenogram. Shedding extended for a significantly longer time in infants with lower respiratory tract disease than in those with clinical manifestations limited to the upper respiratory tract.