Nasal quantity of respiratory syncytial virus correlates with disease severity in hospitalized infants

Objective, To evaluate the relationship between nasal quantity of respirato ry syncytial virus (RSV) and disease severity in hospitalized infants witho ut underlying cardiopulmonary disease or immunodeficiency. Methods. Nasal aspirates were obtained from hospitalized infants <24 months of age with recently identified RSV infection and evaluated for RSV quanti ty by a standard plaque assay on HEp-2 cell monolayers. Subjects were class ified as having "severe" disease if they required mechanical ventilation at the time of sample collection and as having "nonsevere" disease if they di d not, Linear modeling was used to determine the relationship between nasal RSV quantity and various independent variables, including disease severity . Results, Nasal aspirates from 39 patients were evaluated, Age, gender and m ean duration of time from symptom onset to sample acquisition (5 days) were similar between the severe (n = 15) and nonsevere (n = 24) groups. Signifi cantly more infants were born at <35 weeks gestation in the severe disease group (7 of 15 vs. 3 of 24, P = 0.017), and infants born at <35 weeks gesta tion were significantly more likely to be of non-Caucasian ethnicity than w ere infants born at greater than or equal to 35 weeks gestation (8 of 10 vs . 12 of 29, P = 0.035), The linear model found that higher nasal RSV quanti ties were associated with severe disease [mean +/- SEM, 5.06 +/- 0.34 log p laque-forming units (pfu)/ml vs. 3.91 +/- 0.35 log pfu/ml, P = 0.022], gest ational age greater than or equal to 35 weeks (5.44 +/- 0.27 log pfu/ml us. 3.52 +/- 0.45 log pfu/ml, P = 0.002) and non-Caucasian ethnicity (5.16 +/- 0.30 log pfu/ml vs. 3.80 +/- 0.37 log pfu/ml, P = 0.006). Conclusions. Nasal RSV quantity correlates with disease severity in hospita lized infants with recently identified RSV infection.