BackgroundIn Latin America, community-acquired pneumonia remains a major cause of morbidity and mortality among children. Few studies have examined the etiology of pneumonia in Ecuador.MethodsThis observational study was part of a randomized, double blind, placebo-controlled clinical trial conducted among children aged 2–59 months with severe pneumonia in Quito, Ecuador. Nasopharyngeal and blood samples were tested for bacterial and viral etiology by polymerase chain reaction. Risk factors for specific respiratory pathogens were also evaluated.ResultsAmong 406 children tested, 159 (39.2%) had respiratory syncytial virus (RSV), 71 (17.5%) had human metapneumovirus (hMPV), and 62 (15.3%) had adenovirus. Streptococcus pneumoniae was identified in 37 (9.2%) samples and Mycoplasma pneumoniae in three (0.74%) samples. The yearly circulation pattern of RSV (P = 0.0003) overlapped with S. pneumoniae, (P = 0.03) with most cases occurring in the rainy season. In multivariable analysis, risk factors for RSV included younger age (adjusted odds ratio [aOR] = 1.9, P = 0.01) and being underweight (aOR = 1.8, P = 0.04). Maternal education (aOR = 0.82, P = 0.003), pulse oximetry (aOR = 0.93, P = 0.005), and rales (aOR = 0.25, P = 0.007) were associated with influenza A. Younger age (aOR = 3.5, P = 0.007) and elevated baseline respiratory rate were associated with HPIV-3 infection (aOR = 0.94, P = 0.03).ConclusionThese results indicate the importance of RSV and influenza, and potentially modifiable risk factors including undernutrition and future use of a RSV vaccine, when an effective vaccine becomes available.Trial registrationClinicalTrials.gov NCT 00513929

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