title: Respiratory Viral Detections During Symptomatic and Asymptomatic Periods in Young Andean Children.
abstract: BACKGROUND
  Viruses are commonly detected in children with acute respiratory illnesses (ARIs) and in asymptomatic children. Longitudinal studies of viral detections during asymptomatic periods surrounding ARI could facilitate interpretation of viral detections but are currently scant.
  
  
  METHODS
  We used reverse transcription polymerase chain reaction to analyze respiratory samples from young Andean children for viruses during asymptomatic periods within 8-120 days of index ARI (cough or fever). We compared viral detections over time within children and explored reverse transcription polymerase chain reaction cycle thresholds (CTs) as surrogates for viral loads.
  
  
  RESULTS
  At least 1 respiratory virus was detected in 367 (43%) of 859 samples collected during asymptomatic periods, with more frequent detections in periods with rhinorrhea (49%) than those without (34%, P < 0.001). Relative to index ARI with human rhinovirus (HRV), adenovirus (AdV), respiratory syncytial virus (RSV) and parainfluenza virus detected, the same viruses were also detected during 32, 22, 10 and 3% of asymptomatic periods, respectively. RSV was only detected 8-30 days after index RSV ARI, whereas HRV and AdV were detected throughout asymptomatic periods. Human metapneumovirus and influenza were rarely detected during asymptomatic periods (<3%). No significant differences were observed in the CT for HRV or AdV during asymptomatic periods relative to ARI. For RSV, CTs were significantly lower during ARI relative to the asymptomatic period (P = 0.03).
  
  
  CONCLUSIONS
  These findings indicate that influenza, human metapneumovirus, parainfluenza virus and RSV detections in children with an ARI usually indicate a causal relationship. When HRV or AdV is detected during ARI, the causal relationship is less certain.
authors.affiliation: From the *Division of Infectious Diseases, Department of Pediatrics, Vanderbilt University, Nashville, Tennessee; †Vanderbilt Vaccine Research Program, Nashville, Tennessee; ‡Department of Pathology, Microbiology, and Immunology, Vanderbilt University, Nashville, Tennessee; §Department of Biostatistics, Vanderbilt University, Nashville, Tennessee; ¶Instituto de Investigacion Nutricional, Lima, Peru; and ‖Department of Health Policy, Vanderbilt University, Nashville, Tennessee.
authors.forename: Leigh M
authors.initials: LM
authors.lastname: Howard
authors.forename: Monika
authors.initials: M
authors.lastname: Johnson
authors.forename: John V
authors.initials: JV
authors.lastname: Williams
authors.forename: Yuwei
authors.initials: Y
authors.lastname: Zhu
authors.forename: Ana I
authors.initials: AI
authors.lastname: Gil
authors.forename: Kathryn M
authors.initials: KM
authors.lastname: Edwards
authors.forename: Marie R
authors.initials: MR
authors.lastname: Griffin
authors.forename: Claudio F
authors.initials: CF
authors.lastname: Lanata
authors.forename: Carlos G
authors.initials: CG
authors.lastname: Grijalva
mesh_terms: D002648:Child; D006801:Humans; D010568:Peru; D011897:Random Allocation; D012141:Respiratory Tract Infections / Q000175:diagnosis* / Q000821:virology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019562:Viral Load / Q000379:methods*; D014780:Viruses / Q000235:genetics* / Q000302:isolation & purification