A Hypothesis-Generating Prospective Longitudinal Study to Assess the Relative Contribution of Common Respiratory Viruses to Severe Lower Respiratory Infections in Young Children.

Abstract

Respiratory viruses such as respiratory syncytial virus (RSV), influenza, parainfluenza and human metapneumovirus are well-established etiologies of acute lower respiratory tract infections (ALRIs; LRI-viruses). In contrast, adenovirus (AdV), rhinovirus/enterovirus (RV/EV) and seasonal human coronaviruses (CoV), collectively termed AdV/RV/CoV, are detected both in healthy children and children with ALRI. The methods include a prospective longitudinal case-control study, assessing the prevalence of LRI-viruses versus AdV/RV/CoV in ALRI [community-acquired alveolar pneumonia (CAAP) and bronchiolitis] during hospitalization (visit 1), 7-14 days (visit 2) and 28-35 days (visit 3) in 2-17-month-old children. Controls were 2-27-month-old children hospitalized for elective surgery during the same respiratory seasons. We enrolled 99 infants (37 CAAP, 38 bronchiolitis and 24 controls) and obtained 211 nasopharyngeal swabs. Overall, 163 (77%) had greater than or equal to 1 viruses detected; RV/EV (n = 94; 45%) and RSV (n = 71; 34%) were the most frequently detected viruses. In CAAP, the overall LRI-virus prevalence was 78.4%, 32.4% and 5.4% in visits 1, 2 and 3, respectively; the respective rates in bronchiolitis were 73.7%, 34.5% and 8.0%. In controls, no LRI-viruses were detected. In contrast, the overall AdV/RV/CoV prevalence was high among controls (70.8%) and similar among CAAP (48.6%, 40.5% and 40.5%) and bronchiolitis (47.4, 58.6% and 64.0%) across visits. Among ALRI cases, LRI-viruses dominated during the acute disease, with prevalence declining within 28-35 days, suggesting their causative role. In contrast, AdV/RV/CoV prevalence was similar during all 3 visits and in controls, suggesting that carriage of these viruses is common during the viral respiratory season. The current study is relatively small and of short duration; however, the findings are supported by other recent studies.