title: Epidemiological and genetic characteristics associated with the severity of acute viral bronchiolitis by respiratory syncytial virus.
abstract: OBJECTIVE
  to assess the epidemiological and genetic factors associated with severity of acute viral bronchiolitis (AVB) by respiratory syncytial virus (RSV).
  
  
  METHODS
  the key words "bronchiolitis", "risk factor", "genetics" and "respiratory syncytial virus", and all combinations among them were used to perform a search in the PubMed, SciELO, and Lilacs databases, of articles published after the year 2000 that included individuals younger than 2 years of age.
  
  
  RESULTS
  a total of 1,259 articles were found, and their respective summaries were read. Of these, 81 were selected, which assessed risk factors for the severity of AVB, and were read in full; the 60 most relevant studies were included. The epidemiologic factors associated with AVB severity by RSV were prematurity, passive smoking, young age, lack of breastfeeding, chronic lung disease, congenital heart disease, male gender, ethnicity, viral coinfection, low weight at admission, maternal smoking during pregnancy, atopic dermatitis, mechanical ventilation in the neonatal period, maternal history of atopy and/or asthma during pregnancy, season of birth, low socioeconomic status, Down syndrome, environmental pollution, living at an altitude > 2,500 meters above sea level, and cesarean section birth. Conversely, some children with severe AVB did not present any of these risk factors. In this regard, recent studies have verified the influence of genetic factors on the severity of AVB by RSV. Polymorphisms of the TLRs, RANTES, JUN, IFNA5, NOS2, CX3CR1, ILs, and VDR genes have been shown to be associated with more severe evolution of AVB by RSV.
  
  
  CONCLUSIONS
  the severity of AVB by RSV is a phenomenon that depends on the varying degrees of interaction among epidemiological, environmental, and genetic variables.
authors.affiliation: Pediatrics Department, Faculdade de Ciências Médicas, Universidade Estadual de Campinas, Campinas, SP, Brazil.
authors.forename: Alfonso Eduardo
authors.initials: AE
authors.lastname: Alvarez
authors.forename: Fernando Augusto de Lima
authors.initials: FA
authors.lastname: Marson
authors.forename: Carmen Sílvia
authors.initials: CS
authors.lastname: Bertuzzo
authors.forename: Clarice Weis
authors.initials: CW
authors.lastname: Arns
authors.forename: José Dirceu
authors.initials: JD
authors.lastname: Ribeiro
mesh_terms: D000367:Age Factors; D001942:Breast Feeding; D001990:Bronchiolitis, Viral / Q000453:epidemiology* / Q000208:ethnology / Q000209:etiology / Q000235:genetics*; D002908:Chronic Disease; D005260:Female; D006331:Heart Diseases / Q000151:congenital; D006801:Humans; D007223:Infant; D007234:Infant, Premature; D055370:Lung Injury; D008297:Male; D018357:Respiratory Syncytial Virus Infections / Q000150:complications*; D012136:Respiratory Syncytial Viruses; D012307:Risk Factors; D012720:Severity of Illness Index; D012737:Sex Factors; D014028:Tobacco Smoke Pollution / Q000009:adverse effects*
chemical_list: D014028:Tobacco Smoke Pollution
keywords: Bronchiolitis; Bronquiolite; Fatores de risco; Genetics; Genética; Respiratory syncytial virus; Risk factors; Vírus sincicial respiratório