The evolution of the hygiene hypothesis: the role of early-life exposures to viruses and microbes and their relationship to asthma and allergic diseasesDaley, DeniseCurrent Opinion in Allergy and Clinical Immunology: October 2014 - Volume 14 - Issue 5 - p 390–396 doi: 10.1097/ACI.0000000000000101 GENETICS AND EPIDEMIOLOGY: Edited by Catherine Laprise and Emmanuelle Bouzigon Abstract Author Information Purpose of review 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. Recent findings 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 3He 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. Summary 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. 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 Correspondence to Dr Denise Daley, University of British Columbia (UBC) Centre for Heart and Lung Innovation, Providence Heart + Lung Institute, St Paul's Hospital, 1081 Burrard Street, Room 166, Vancouver, BC V6G 1Y6, Canada. Tel: +1 604 682 2344; e-mail: firstname.lastname@example.org Copyright © 2014 Wolters Kluwer Health, Inc. All rights reserved.