title: Roles of sunlight and natural ventilation for controlling infection: historical and current perspectives.
abstract: BACKGROUND
  Infections caught in buildings are a major global cause of sickness and mortality. Understanding how infections spread is pivotal to public health yet current knowledge of indoor transmission remains poor.
  
  
  OBJECTIVE
  To review the roles of natural ventilation and sunlight for controlling infection within healthcare environments.
  
  
  METHODS
  Comprehensive literature search was performed, using electronic and library databases to retrieve English language papers combining infection; risk; pathogen; and mention of ventilation; fresh air; and sunlight. Foreign language articles with English translation were included, with no limit imposed on publication date.
  
  
  RESULTS
  In the past, hospitals were designed with south-facing glazing, cross-ventilation and high ceilings because fresh air and sunlight were thought to reduce infection risk. Historical and recent studies suggest that natural ventilation offers protection from transmission of airborne pathogens. Particle size, dispersal characteristics and transmission risk require more work to justify infection control practices concerning airborne pathogens. Sunlight boosts resistance to infection, with older studies suggesting potential roles for surface decontamination.
  
  
  CONCLUSIONS
  Current knowledge of indoor transmission of pathogens is inadequate, partly due to lack of agreed definitions for particle types and mechanisms of spread. There is recent evidence to support historical data on the effects of natural ventilation but virtually none for sunlight. Modern practice of designing healthcare buildings for comfort favours pathogen persistence. As the number of effective antimicrobial agents declines, further work is required to clarify absolute risks from airborne pathogens along with any potential benefits from additional fresh air and sunlight.
authors.affiliation: Department of Microbiology, Hairmyres Hospital, East Kilbride, Lanarkshire G75 8RG, UK.
authors.forename: R A
authors.initials: RA
authors.lastname: Hobday
authors.forename: S J
authors.initials: SJ
authors.lastname: Dancer
mesh_terms: D003428:Cross Infection / Q000517:prevention & control*; D004203:Disinfection / Q000379:methods*; D004783:Environmental Microbiology; D006268:Health Facilities; D006801:Humans; D013472:Sunlight; D014691:Ventilation
keywords: Airborne pathogens; Airborne transmission; Airborne transmission of infection; Hospital-acquired infection; Sunlight; Ventilation