title: Rhinovirus transmission within families with children: incidence of symptomatic and asymptomatic infections.
abstract: BACKGROUND
  Rhinoviruses are the most common cause of respiratory tract infections, but the transmission in families has not been studied using sensitive and specific molecular detection methods.
  
  
  METHODS
  Children hospitalized for any infection were screened for rhinoviruses. Eight families with a rhinovirus-positive index child and 16 families with a rhinovirus-negative index child were monitored for 3 weeks for disease symptoms, and the presence and quantity of rhinoviruses in nasal swab samples were determined by quantitative reverse transcription-polymerase chain reaction. Rhinoviruses were further identified by melting temperature and partial sequence analysis.
  
  
  RESULTS
  The rates of rhinovirus infection were 1.00 cases per person among the 17 siblings and 0.50 cases per person among the 14 parents of rhinovirus-positive index patients; the rates were 0.54 cases per person among the 24 siblings and 0.23 cases per person among the 30 parents of rhinovirus-negative index patients. Symptomatic infections were associated with an age of <7 years but not with a high copy number of rhinovirus genomes. Virus typing revealed the transmission routes of the viruses and showed that several virus types could circulate in the families simultaneously.
  
  
  CONCLUSIONS
  Rhinoviruses are frequently transmitted from children to other family members. Most rhinovirus infections in young children are symptomatic, but secondary infections in adults are often asymptomatic. Multiple virus types circulate simultaneously in families.
authors.affiliation: Department of Pediatrics, Turku University Hospital, Turku, Finland. ville.peltola@utu.fi
authors.forename: Ville
authors.initials: V
authors.lastname: Peltola
authors.forename: Matti
authors.initials: M
authors.lastname: Waris
authors.forename: Riikka
authors.initials: R
authors.lastname: Osterback
authors.forename: Petri
authors.initials: P
authors.lastname: Susi
authors.forename: Olli
authors.initials: O
authors.lastname: Ruuskanen
authors.forename: Timo
authors.initials: T
authors.lastname: Hyypiä
mesh_terms: D000328:Adult; D002648:Child; D003139:Common Cold / Q000453:epidemiology* / Q000635:transmission*; D005190:Family; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D009297:Nasal Mucosa / Q000821:virology; D010290:Parents; D012137:Respiratory System / Q000821:virology; D012229:Rhinovirus / Q000145:classification / Q000302:isolation & purification; D035781:Siblings