title: Climatic factors and lower respiratory tract infection due to respiratory syncytial virus in hospitalised infants in northern Spain.
abstract: OBJECTIVE
  To analyse the influence of climatic factors on the number of hospitalised infants with respiratory syncytial virus (RSV) per week.
  
  
  METHODS
  A retrospective observational case-control study was designed enrolling infants under 2 years of age, admitted to hospital between October 1995 and June 2000 with lower respiratory tract infection due to RSV. Climatic and seasonal data were included. The week variable was used as the study unit: weeks with more than one admission for the case group and weeks without admissions for the control group. The total number of weeks excluding summer months, from June to September, was 174.
  
  
  RESULTS
  A total of 167 infants were admitted to hospital with lower respiratory tract infection due to RSV with a peak in January and February. There was 82 weeks with one or more admissions (case group) and 92 without admissions (control group). The case group demonstrated lower levels of humidity (absolute: 5.6 +/- 1.5 vs. 6.5 +/- 1.5; p < 0.001) and lower temperature (ground level: 0.4 +/- 3.2 vs. 2.2 +/- 3.5; p < 0.001). When climatic factors were analysed in a logistic regression model, absolute humidity (p < 0.001) was an independent variable associated with a higher risk of infection.
  
  
  CONCLUSIONS
  Low absolute humidity was independently associated with hospital admission of infants with lower respiratory tract infection due to RSV.
authors.affiliation: Pediatric Service, Microbiological Service, Hospital of Leon, Leon, Spain. slapena@hleo.sacyl.es
authors.forename: Santiago
authors.initials: S
authors.lastname: Lapeña
authors.forename: Mariá Belén
authors.initials: MB
authors.lastname: Robles
authors.forename: Leticia
authors.initials: L
authors.lastname: Castañón
authors.forename: Juan Pablo
authors.initials: JP
authors.lastname: Martínez
authors.forename: Sofiá
authors.initials: S
authors.lastname: Reguero
authors.forename: María Paz
authors.initials: MP
authors.lastname: Alonso
authors.forename: Isabel
authors.initials: I
authors.lastname: Fernández
mesh_terms: D016022:Case-Control Studies; D002980:Climate; D005260:Female; D006760:Hospitalization; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008137:Longitudinal Studies; D008297:Male; D018357:Respiratory Syncytial Virus Infections / Q000453:epidemiology*; D012136:Respiratory Syncytial Viruses; D012189:Retrospective Studies; D012307:Risk Factors; D013030:Spain / Q000453:epidemiology