title: Croup is associated with the novel coronavirus NL63.
abstract: BACKGROUND
  The clinical relevance of infections with the novel human coronavirus NL63 (HCoV-NL63) has not been investigated systematically. We therefore determined its association with disease in young children with lower respiratory tract infection (LRTI).
  
  
  RESULTS
  Nine hundred forty-nine samples of nasopharyngeal secretions from children under 3 y of age with LRTIs were analysed by a quantitative HCoV-NL63-specific real-time PCR. The samples had been collected from hospitalised patients and outpatients from December 1999 to October 2001 in four different regions in Germany as part of the prospective population-based PRI.DE study and analysed for RNA from respiratory viruses. Forty-nine samples (5.2%), mainly derived from the winter season, were positive for HCoV-NL63 RNA. The viral RNA was more prevalent in samples from outpatients (7.9%) than from hospitalised patients (3.2%, p = 0.003), and co-infection with either respiratory syncytial virus or parainfluenza virus 3 was observed frequently. Samples in which only HCoV-NL63 RNA could be detected had a significantly higher viral load than samples containing additional respiratory viruses (median 2.1 x 10(6) versus 2.7 x 10(2) copies/ml, p = 0.0006). A strong association with croup was apparent: 43% of the HCoV-NL63-positive patients with high HCoV-NL63 load and absence of co-infection suffered from croup, compared to 6% in the HCoV-NL63-negative group, p < 0.0001. A significantly higher fraction (17.4%) of samples from croup patients than from non-croup patients (4.2%) contained HCoV-NL63 RNA.
  
  
  CONCLUSIONS
  HCoV-NL63 infections occur frequently in young children with LRTI and show a strong association with croup, suggesting a causal relationship.
authors.affiliation: Department of Human Retrovirology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands. c.m.vanderhoek@amc.uva.nl
authors.forename: Lia
authors.initials: L
authors.lastname: van der Hoek
authors.forename: Klaus
authors.initials: K
authors.lastname: Sure
authors.forename: Gabriele
authors.initials: G
authors.lastname: Ihorst
authors.forename: Alexander
authors.initials: A
authors.lastname: Stang
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Pyrc
authors.forename: Maarten F
authors.initials: MF
authors.lastname: Jebbink
authors.forename: Gudula
authors.initials: G
authors.lastname: Petersen
authors.forename: Johannes
authors.initials: J
authors.lastname: Forster
authors.forename: Ben
authors.initials: B
authors.lastname: Berkhout
authors.forename: Klaus
authors.initials: K
authors.lastname: Uberla
mesh_terms: D002675:Child, Preschool; D017934:Coronavirus / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D003440:Croup / Q000821:virology*; D005260:Female; D005858:Germany; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007297:Inpatients; D008297:Male; D010045:Outpatients; D010224:Parainfluenza Virus 3, Human / Q000235:genetics / Q000302:isolation & purification*; D012367:RNA, Viral / Q000378:metabolism*; D018113:Respiratory Syncytial Virus, Human / Q000235:genetics / Q000302:isolation & purification*; D012141:Respiratory Tract Infections / Q000821:virology*; D012621:Seasons; D013997:Time Factors; D019562:Viral Load
chemical_list: D012367:RNA, Viral