title: The evolution of the hygiene hypothesis: the role of early-life exposures to viruses and microbes and their relationship to asthma and allergic diseases.
abstract: OBJECTIVE
  Understanding the mechanisms involved in the development of asthma and allergic diseases is expanding, due in part to sequencing advances that have led to the identification of new viral strains such as human rhinovirus strain C (HRV-C) and the human microbiome project.
  
  
  RESULTS
  Recent studies have identified new ways in which viral and microbial exposures in early life interact with host genetic background/variants to modify the risk for developing asthma and allergic diseases. Recent research suggests that HRV-C is the main pathogenic agent associated with infant wheeze, hospitalizations and likely the subsequent development of asthma. Pulmonary He MRI suggests that HRV infection in early childhood and subsequent immune responses initiate airway remodeling. Numerous studies of the microbiome indicate that intestinal and airway microbiome diversity and composition contribute to the cause of asthma and allergic diseases.
  
  
  CONCLUSIONS
  Susceptibility to asthma and allergic diseases is complex and involves genetic variants and environmental exposures (bacteria, viruses, smoking, and pet ownership), alteration of our microbiome and potentially large-scale manipulation of the environment over the past century.
authors.affiliation: Faculty of Medicine, University of British Columbia (UBC) Centre for Heart and Lung Innovation, Providence Heart + Lung Institute, St Paul's Hospital, Vancouver, British Columbia, Canada.
authors.forename: Denise
authors.initials: D
authors.lastname: Daley
mesh_terms: D056151:Airway Remodeling; D001249:Asthma / Q000209:etiology / Q000276:immunology*; D001419:Bacteria / Q000276:immunology*; D004781:Environmental Exposure / Q000009:adverse effects; D059647:Gene-Environment Interaction; D054884:Host-Pathogen Interactions; D006801:Humans; D061148:Hygiene Hypothesis; D006967:Hypersensitivity / Q000209:etiology / Q000276:immunology*; D018928:Immunity, Mucosal; D007223:Infant; D007231:Infant, Newborn; D007239:Infections / Q000150:complications / Q000276:immunology*; D064307:Microbiota; D014780:Viruses / Q000276:immunology*