{"id":948,"date":"2020-09-22T15:01:22","date_gmt":"2020-09-22T22:01:22","guid":{"rendered":"http:\/\/wordpress.kpu.ca\/camidanser\/?p=948"},"modified":"2020-10-15T21:03:56","modified_gmt":"2020-10-16T04:03:56","slug":"roles-of-sunlight-and-natural-ventilation-for-controlling-infection-historical-and-current-perspectives","status":"publish","type":"post","link":"https:\/\/wordpress.kpu.ca\/camidanser\/roles-of-sunlight-and-natural-ventilation-for-controlling-infection-historical-and-current-perspectives\/","title":{"rendered":"Roles of sunlight and natural ventilation for controlling infection: historical and current perspectives"},"content":{"rendered":"\n<p class=\"wp-block-paragraph\"><strong>Article Review: <\/strong>Roles of Sunlight and Natural Ventilation for Controlling Infection: Historical and Current Perspectives &#8211; Journal of Hospital Infection<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Intro:&nbsp;<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>Evidence supporting that fresh air and sunlight coming into buildings can influence transmission of airborne pathogens<\/li><li>Mostly used before discovery of antibiotics&nbsp;<\/li><li>With microbial resistance increasing, may be worth it to go back to pre-antibiotic strategies&nbsp;<\/li><li>Particles of different sizes pose different threats, have different practices for preventing transmission<\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>History:&nbsp;<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>Britain emphasised importance of natural ventilation in hospital wards, at the time smallpox and other diseases were believed to be transmitted via airborne matter<\/li><li>Recommended to change the air rate on Royal Navy ships and in British housing<\/li><li>As improvements to living conditions and strategies for preventing infections were made, ventilation became of lesser importance than comfort of patients<\/li><li>Increased use of recirculated air in commercial buildings saved fuel and money, but contributed to <strong><span style=\"color:#345663\" class=\"has-inline-color\">\u2018sick building syndrome\u2019<\/span><\/strong> which caused headaches, fatigue, dry eyes and throat, nasal congestion and dry skin in some people<\/li><li>Virus outbreaks of legionella pneumophila and SARS brought back interest in indoor air quality<\/li><\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">Mechanisms for airborne transmission of pathogens<\/h3>\n\n\n\n<ul class=\"wp-block-list\"><li>4 mechanisms of transmission<ul><li>Contact, dust, \u2018respiratory droplets\u2019 and \u2018droplet nuclei\u2019<\/li><\/ul><\/li><li>Potential for transmission depends on number of particles produces, velocity which they are produced, number of micro-organisms contained, longevity of microbes and proximity of potential carriers or targets<\/li><li>Respiratory droplets fall to surfaces can contribute to dust<ul><li>Dust particles can be suspended in air, fall, and then resuspended upon surrounding movement&nbsp;<\/li><\/ul><\/li><li>Range of these droplets is ~1m, those beyond do not require protection&nbsp;<\/li><li>Smaller respiratory droplets evaporate quickly, leaving residues like \u2018droplet nuclei\u2019<\/li><li>Droplet nuclei also expelled via breathing and talking<\/li><li>Smaller particles stay airborne for longer periods of time, increasing risk of deeper penetration of lung tissue than larger droplets<\/li><li>No specific classification of airborne particles, no universal diameter of droplets&nbsp;<\/li><li>Survival of airborne pathogens depends on ambient factors; temperature, humidity, UV radiation, pollutants etc.&nbsp;<\/li><li>Movement of airborne droplets affected by environmental factors; ventilation airflows, door opening, movement of people and clothes, thermal gradients from electrical equipment etc.&nbsp;<\/li><li>Healthcare facilities require<strong> use of negative pressure isolation rooms<\/strong> for patients with airborne infections, those entering must wear a <strong>high filtration respirator<\/strong> (not just surgical face mask)<\/li><li>Does not necessarily apply to diseases spread via droplets (influenza virus, rhinoviruses, adenoviruses, respiratory syncytial virus)&nbsp;<\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Influenza:<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>Knowledge on transmission and control is limited<\/li><li>Assumed that influenza is transmitted by large droplets, current infection control based on this<\/li><li>Possibility of aerosol transmission that is the cause of severe cases affecting lower respiratory tract<\/li><li>Aerosol transmission important to consider for H5N1, which was formerly believed to only transmit via physical contact<\/li><li>Potential for human pandemic influenza, necessary to revise current infection control practices<\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Smallpox:&nbsp;<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>Previously believe to be airborne&nbsp;<\/li><li>WHOs campaign to eliminate smallpox based on assumption that smallpox was spread via face-to-face contact&nbsp;<\/li><li>1970 outbreak in Germany pattern suggested virus transmitted via airborne transmission<\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>SARS (severe acute respiratory syndrome):<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>2003 epidemic assumed to be transmitted via direct contact<\/li><li>SARS shed in large numbers, remained on surfaces for long periods of time&nbsp;<\/li><li>Avoiding face-to-face contact decreased risk for spread&nbsp;<\/li><li>Outbreak in Hong Kong suggested that airborne transmission was also relevant<\/li><li><strong><span style=\"color:#345663\" class=\"has-inline-color\">Investigation discovered contaminated air rose up ventilation shafts and winds carried it to adjacent buildings&nbsp;<\/span><\/strong><\/li><li>Faulty ventilation and transmission on aircrafts suggested that airborne droplets were the culprit of infection&nbsp;<\/li><li>Before SARS little research had been done, and confirmed <strong><span style=\"color:#345663\" class=\"has-inline-color\">mechanisms of respiratory disease transmission are not fully understood<\/span><\/strong><\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Hantavirus:<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>Spread to humans from inhalation of expired matter from wild rodents<\/li><li>Key preventative measure: disposable respirators and gloves while cleaning following ventilation process<\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Common cold:<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>Adults acquire 2-5 colds a year, caused by rhinoviruses<\/li><li>Transmission remains controversial, after years of research<\/li><li>Evidence showing that shared office spaces increases likelihood of catching a cold<\/li><li>In <strong><span style=\"color:#345663\" class=\"has-inline-color\">mechanically ventilated office buildings, lower outdoor air supply increases risk of inhaling infectious droplets<\/span><\/strong><\/li><li>Hand-to-hand contact of greater significance, although ventilation important in diluting and dispersing droplets<\/li><\/ul>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\"><p>\u201cA more recent study found that students accommodated in six-person rooms were twice as likely to have colds as students in three-person rooms. Some 35% of students caught more than six colds each year when the ventilation rate was 1 L\/s\/person. If this rate was increased to 5 L\/s\/person, the number of students catching colds six times or more fell to 5%, suggesting that there was an association between colds and outdoor-to-indoor air flow rates; this reflects the multifactorial nature of the spread of such respiratory infections.\u201d<\/p><cite>R.a. hobday, s.j. dancer<\/cite><\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Tuberculosis:<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>Greatest transmission occurs indoors<\/li><li>Improved housing has declined number of cases&nbsp;<\/li><li>Contracted via airborne droplets, especially in instances of overcrowding and poor ventilation<\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Staphylococcus aureus (MRSA):<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>Transmission via hand contact is the main vehicle of transmission, airborne transmission does contribute<\/li><li>Linked to shedding of skin cells from infected patients<\/li><li>Inhaling air causes nasal cavities to be colonized with S. aureus<\/li><li>Increased risk of transmission where more people-traffic and bed making&nbsp;<\/li><li>Burn patients more susceptible with airborne transmission<\/li><\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">Preventing infection through ventilation&nbsp;<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Open air:&nbsp;<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>\u201cThe majority of microbes that cause airborne infections cannot tolerate sunlight, oxidants or the temperature extremes that occur outdoors.\u201d<\/li><li>Wards designed to be as closed off from the outdoors as possible&nbsp;<\/li><li>High ventilation rates dilute number of pathogens in the air<\/li><li>However, exposure to fresh air reduced the presence of tubercle bacillus, opposed to being in a well-ventilated dark space&nbsp;<\/li><li>OAF&nbsp; \u2018open air factor\u2019 introduced in the 1960s after rediscovery that outdoor air had significant effect on the viability and virulence of airborne micro-organisms<\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Open windows:<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>Natural ventilation, low cost and low maintenance<\/li><li>Multiple routes for air to enter&nbsp;<\/li><li>No guarantee of regular usage to encourage air movement<\/li><li>Not favourable to keep windows open during unfavourable weather&nbsp;<\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Natural vs. mechanical ventilation:<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>Some evidence showing that natural ventilation is more effective that mechanical in the prevention of transmission<\/li><li>Operation desert shield &#8211; respiratory tract infections in military personnel less frequent among those in tents and more frequent among those in barracks<\/li><li>2007 study on natural ventilation in 70 rooms with tuberculosis patients;&nbsp;<\/li><\/ul>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\"><p>\u201cThe highest risk of infection occurred in mechanically ventilated rooms with sealed windows, despite being ventilated at recommended rates. By contrast, clinical rooms with high ceilings and multiple large windows in pre-1950 hospitals gave the greatest protection, even if the windows were only partially open.\u201d<\/p><cite>R.A. HOBDAY, S.J. DANCER<\/cite><\/blockquote>\n\n\n\n<ul class=\"wp-block-list\"><li>Natural ventilation wards capable of achieving higher air change rates in comparison to mechanically ventilated rooms; 69 air changes per hours vs 12 air changes per hour&nbsp;<\/li><li>Studies in china show that cross-ventilation and isolation rooms with operable windows more effective at preventing outbreak of SARS&nbsp;<\/li><\/ul>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\"><p>\u201cVentilation systems in hospitals may be compromised by poor design, construction or inadequate maintenance, and these failings have been implicated in outbreaks of tuberculosis. Contaminated hospital ventilation systems have also been blamed for other types of outbreak.\u201d<\/p><cite>R.A. HOBDAY, S.J. DANCER<\/cite><\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Ventilation in the home:<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>Germans, Canadians and Americans spend most of their time indoors in private homes<\/li><li>Estimated that in one\u2019s lifetime, half the body;s air intake is inspired indoors<\/li><li>No evidence that mechanical ventilation facilitates spread of infection in homes although there has been increased use in Britain and other countries<\/li><li>2012 study of mechanically ventilated Dutch homes; dust and dirt present in air supply ducts in 67% of homes, dirty air filters in almost half, insufficient ventilation in at least one room, recirculation of exhaust air in over half the houses<ul><li>Ventilation systems not controlled or on highest ventilation settings as recommended due to noise levels<\/li><\/ul><\/li><\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">Preventing infection by sunlight<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Historical background:<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>Sunlight inhibited the growth of bacteria from behind glass, Downes and Blunt 1877<\/li><li>Later studies, sunlight could kill range of bacteria; tetanus, typhoid, anthrax, tuberculosis<\/li><li>Direct sunlight could kill the bacillus in a few minutes to several hours depending on thickness of glass, Koch 1890&nbsp;<\/li><li>&nbsp;Diffused daylight can kill bacteria in 5-7 days&nbsp;<\/li><li>1920s glass produced that transmitted more UV radiation<\/li><li>1930s tests done with various glass and bactericidal powder, almost three quarters of S. aureus were killed by unfiltered sunlight, half died when <em>Vitaglass <\/em>was used, one quarter died when ordinary glass was used; still unverified and not recently explored<\/li><li>WHO guidelines hospital infections; patients placed in single rooms with sunlight, negative air pressure 6-12 air changes per hour&nbsp;<\/li><li>WHO guidelines for healthy housing; toilets should have access to natural light with use of glass which transmits higher proportion of UV rays<\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Disinfection with artificial light:<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>UV rays inactivate micro-organisms, absorption of UV rays can lead to mutations or cell death&nbsp;<\/li><li>High intensity narrow spectrum light (HINS-light) modern light-based disinfection method, affects range of bacteria<ul><li>Has been assessed for its efficacy in decontamination but not linked to lowering rates of hospital infection&nbsp;<\/li><\/ul><\/li><li>Direct sunlight can enhance personal well-being and resistance to infection&nbsp;<\/li><li>Infra-red radiation speeds up wound-healing and can relieve pain among patients indoors<\/li><li>Infra-red irradiation inactives fungal and other pathogens and MRSA in nasal passages<\/li><\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">Key insights:&nbsp;<\/h3>\n\n\n\n<ul class=\"wp-block-list\"><li>Transmissions <\/li><li>Natural ventilation wards capable of achieving higher air change rates in comparison to mechanically ventilated rooms<\/li><li>Direct sunlight can be lethal to bacteria such as mycobacteria, streptococci, meningococci, staphylococci, diffused light is less effective, the UV rays are what impact the bacteria<\/li><li>Increasing exposure to sunlight and outdoor air in the designs of buildings can be effective and has subsequent health benefits<\/li><\/ul>\n\n\n\n<hr class=\"wp-block-separator is-style-wide\" \/>\n\n\n\n<p class=\"has-small-font-size wp-block-paragraph\">Source: Hobday, R. A., &amp; Dancer, S. J. (2013). Roles of sunlight and natural ventilation for controlling infection: Historical and current perspectives.&nbsp;<em>Journal of Hospital Infection,<\/em>&nbsp;<em>84<\/em>(4), 271-282. doi:10.1016\/j.jhin.2013.04.011<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Article Review: Roles of Sunlight and Natural Ventilation for Controlling Infection: Historical and Current Perspectives &#8211; Journal of Hospital Infection Intro:&nbsp; Evidence supporting that fresh air and sunlight coming into buildings can influence transmission of airborne pathogens Mostly used before discovery of antibiotics&nbsp; With microbial resistance increasing, may be worth it to go back to [&hellip;]<\/p>\n","protected":false},"author":374,"featured_media":1010,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[17,23,59],"tags":[32,31,30,29,33],"class_list":["post-948","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-article-reviews","category-research","category-ventilation","tag-airborne-pathogens","tag-airborne-transmission","tag-mechanical-ventilation","tag-natural-ventilation","tag-sunlight"],"_links":{"self":[{"href":"https:\/\/wordpress.kpu.ca\/camidanser\/wp-json\/wp\/v2\/posts\/948","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/wordpress.kpu.ca\/camidanser\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/wordpress.kpu.ca\/camidanser\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/wordpress.kpu.ca\/camidanser\/wp-json\/wp\/v2\/users\/374"}],"replies":[{"embeddable":true,"href":"https:\/\/wordpress.kpu.ca\/camidanser\/wp-json\/wp\/v2\/comments?post=948"}],"version-history":[{"count":13,"href":"https:\/\/wordpress.kpu.ca\/camidanser\/wp-json\/wp\/v2\/posts\/948\/revisions"}],"predecessor-version":[{"id":1132,"href":"https:\/\/wordpress.kpu.ca\/camidanser\/wp-json\/wp\/v2\/posts\/948\/revisions\/1132"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/wordpress.kpu.ca\/camidanser\/wp-json\/wp\/v2\/media\/1010"}],"wp:attachment":[{"href":"https:\/\/wordpress.kpu.ca\/camidanser\/wp-json\/wp\/v2\/media?parent=948"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wordpress.kpu.ca\/camidanser\/wp-json\/wp\/v2\/categories?post=948"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wordpress.kpu.ca\/camidanser\/wp-json\/wp\/v2\/tags?post=948"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}