Source control (respiratory disease)

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Source control is recommended for members of the general public during severe epidemics, especially in crowded indoor areas such as stores. Coronavirus COVID-19 face mask in supermarket.jpg
Source control is recommended for members of the general public during severe epidemics, especially in crowded indoor areas such as stores.

Source control is a strategy for reducing disease transmission by blocking respiratory secretions produced through speaking, coughing, sneezing [1] or singing. [2] Surgical masks are commonly used for this purpose, with cloth face masks recommended for use by the public only in epidemic situations when there are shortages of surgical masks. [3] [4] In addition, respiratory etiquette such as covering the mouth and nose with a tissue when coughing can be considered source control. [3] In diseases transmitted by droplets or aerosols, understanding air flow, particle and aerosol transport may lead to rational infrastructural source control measures that minimize exposure of susceptible persons. [5]

Contents

Mechanisms

Droplet spread without source control: up to ~8 meters (26 ft) for sneezes and coughs, up to ~2 meters (6.6 ft) for talking. Aerosol spread is much further than this. Droplet transmission ranges for speaking, intubation, and coughing or sneezing.jpg
Droplet spread without source control: up to ~8 meters (26 ft) for sneezes and coughs, up to ~2 meters (6.6 ft) for talking. Aerosol spread is much further than this.

Infections in general may spread by direct contact (for example, shaking hands or kissing), by inhaling infectious droplets in the air (droplet transmission), by inhaling long-lasting aerosols with tiny particles (airborne transmission), and by touching objects with infectious material on their surfaces (fomites). Different diseases spread in different ways; some spread by only some of these routes. For instance, fomite transmission of COVID-19 is thought to be rare while aerosol, droplet and contact transmission appear to be the primary transmission modes, as of April 2021. [7]

Coughs and sneezes can spread airborne droplets up to ~8 meters (26 ft). Speaking can spread droplets up to ~2 meters (6.6 ft). [6] It may be difficult to maintain these distances. For a masked person, or even one sneezing or coughing into a tissue or elbow, these distances are reduced. [8]

Masking any person who may be a source of infectious droplets (or aerosols) thus reduces the unsafe range of physical distances. If a person can be infectious before they are symptomatic and diagnosed, then people who do not yet know if they are infectious may also be a source of infection.

Handwashing helps to protect people against contact transmission, and against indirect droplet transmission. Handwashing removes infectious droplets that their mask caught (from either side) and which transferred to their hands when they touched their mask. [6]

For pathogens transmitted through the air, strategies to block cough air jets and to capture aerosols, e.g. the "Shield & Sink" approach, can be highly effective in minimizing exposure to respiratory secretions. [5]

Contrast with personal protective equipment

An unfiltered exhalation valve (center) lets air out unfiltered. Masks with unfiltered exhalation valves are thus not very effective for source control and require additional measures (such as a well-fitted cloth covering worn over the respirator). Atemluftfilter Einwegmaske.jpg
An unfiltered exhalation valve (center) lets air out unfiltered. Masks with unfiltered exhalation valves are thus not very effective for source control and require additional measures (such as a well-fitted cloth covering worn over the respirator).

While source control protects others from transmission arising from the wearer, personal protective equipment protects the wearer themselves. [9] Cloth face masks can be used for source control but are not considered personal protective equipment [1] [9] as they have low filter efficiency (generally varying between 2–60%), although they are easy to obtain and reusable after washing. [3] [10] There are no standards or regulation for self-made cloth face masks. [3]

Surgical masks are designed to protect against splashes and sprays, [4] but do not provide complete respiratory protection from germs and other contaminants because of the loose fit between the surface of the face mask and the face. [11] Surgical masks are regulated by various national standards to have high bacterial filtration efficiency (BFE). [12] [13] [14] N95/N99/N100 masks and other filtering facepiece respirators can provide source control in addition to respiratory protection, but respirators with an unfiltered exhalation valve may not provide source control and require additional measures to filter exhalation air when source control is required. [4]

Comparison of face masks by function
TypeSource controlInhaled air filtrationRef
Cloth face mask Brown check.svg SomeDark Red x.svg Bad [1] [3] [9]
Surgical mask or procedure maskGreen check.svg GoodDark Red x.svg Bad [4] [11]
Respirator without exhalation valveGreen check.svg GoodGreen check.svg Good [4]
Respirator with unfiltered exhalation valveDark Red x.svg BadGreen check.svg Good [4]
Respirator with filtered exhalation valveGreen check.svg GoodGreen check.svg Good [4]

COVID-19 pandemic

During the COVID-19 pandemic, cloth face masks for source control have been recommended by the U.S. Centers for Disease Control and Prevention (CDC) for members of the public who leave their homes, and health care facilities are commended to consider requiring face masks for all people who enter the facility. Health care personnel and patients with COVID-19 symptoms are recommended to use surgical masks if available, as they are more protective. [15] Masking patients reduces the personal protective equipment recommended by CDC for health care personnel under crisis shortage conditions. [16]

The World Health Organization and European Centre for Disease Prevention and Control recommend face masks in non-healthcare community settings in severe epidemic situations with a high prevalence of asymptomatic but infectious persons, especially when visiting crowded indoor spaces such as grocery stores, public transportation, and for certain workers who must come into physical proximity with many other people. [3]

Related Research Articles

<span class="mw-page-title-main">Personal protective equipment</span> Equipment designed to help protect an individual from hazards

Personal protective equipment (PPE) is protective clothing, helmets, goggles, or other garments or equipment designed to protect the wearer's body from injury or infection. The hazards addressed by protective equipment include physical, electrical, heat, chemical, biohazards, and airborne particulate matter. Protective equipment may be worn for job-related occupational safety and health purposes, as well as for sports and other recreational activities. Protective clothing is applied to traditional categories of clothing, and protective gear applies to items such as pads, guards, shields, or masks, and others. PPE suits can be similar in appearance to a cleanroom suit.

In medicine, public health, and biology, transmission is the passing of a pathogen causing communicable disease from an infected host individual or group to a particular individual or group, regardless of whether the other individual was previously infected. The term strictly refers to the transmission of microorganisms directly from one individual to another by one or more of the following means:

<span class="mw-page-title-main">Surgical mask</span> Mouth and nose cover against bacterial aerosols

A surgical mask, also known by other names such as a medical face mask or procedure mask, is a personal protective equipment used by healthcare professionals that serves as a mechanical barrier that interferes with direct airflow in and out of respiratory orifices. This helps reduce airborne transmission of pathogens and other aerosolized contaminants between the wearer and nearby people via respiratory droplets ejected when sneezing, coughing, forceful expiration or unintentionally spitting when talking, etc. Surgical masks may be labeled as surgical, isolation, dental or medical procedure masks.

<span class="mw-page-title-main">Respirator</span> Device worn to protect the user from inhaling contaminants

A respirator is a device designed to protect the wearer from inhaling hazardous atmospheres including fumes, vapours, gases and particulate matter such as dusts and airborne pathogens such as viruses. There are two main categories of respirators: the air-purifying respirator, in which respirable air is obtained by filtering a contaminated atmosphere, and the air-supplied respirator, in which an alternate supply of breathable air is delivered. Within each category, different techniques are employed to reduce or eliminate noxious airborne contaminants.

<span class="mw-page-title-main">Respiratory tract infection</span> Infectious disease affecting nose, throat and lungs

Respiratory tract infections (RTIs) are infectious diseases involving the lower or upper respiratory tract. An infection of this type usually is further classified as an upper respiratory tract infection or a lower respiratory tract infection. Lower respiratory infections, such as pneumonia, tend to be far more severe than upper respiratory infections, such as the common cold.

<span class="mw-page-title-main">Isolation (health care)</span> Measure taken to prevent contagious diseases from being spread

In health care facilities, isolation represents one of several measures that can be taken to implement in infection control: the prevention of communicable diseases from being transmitted from a patient to other patients, health care workers, and visitors, or from outsiders to a particular patient. Various forms of isolation exist, in some of which contact procedures are modified, and others in which the patient is kept away from all other people. In a system devised, and periodically revised, by the U.S. Centers for Disease Control and Prevention (CDC), various levels of patient isolation comprise application of one or more formally described "precaution".

<span class="mw-page-title-main">Airborne transmission</span> Disease transmission by airborne particles

Airborne transmission or aerosol transmission is transmission of an infectious disease through small particles suspended in the air. Infectious diseases capable of airborne transmission include many of considerable importance both in human and veterinary medicine. The relevant infectious agent may be viruses, bacteria, or fungi, and they may be spread through breathing, talking, coughing, sneezing, raising of dust, spraying of liquids, flushing toilets, or any activities which generate aerosol particles or droplets. This is the transmission of diseases via transmission of an infectious agent, and does not include diseases caused by air pollution.

Influenza prevention involves taking steps that one can use to decrease their chances of contracting flu viruses, such as the Pandemic H1N1/09 virus, responsible for the 2009 flu pandemic.

<span class="mw-page-title-main">Wells curve</span> Science of medicine

The Wells curve is a diagram, developed by W. F. Wells in 1934, which describes what is expected to happen to small droplets once they have been exhaled into air. Coughing, sneezing, and other violent exhalations produce high numbers of respiratory droplets derived from saliva and/or respiratory mucus, with sizes ranging from about 1 µm to 2 mm. Wells' insight was that such droplets would have two distinct fates, depending on their sizes. The interplay of gravity and evaporation means that droplets larger than a humidity-determined threshold size would fall to the ground due to gravity, while droplets smaller than this size would quickly evaporate, leaving a dry residue that drifts in the air. Since droplets from an infected person may contain infectious bacteria or viruses, these processes influence transmission of respiratory diseases.

<span class="mw-page-title-main">Sneeze guard</span> Acrylic or glass screen designed to protect people or food from exposure to respiratory droplets

A sneeze guard, sneezeguard, or cough shield is an acrylic or glass screen designed to protect food or people from the exposure to respiratory droplets, which are dispensed when coughing, sneezing, or speaking. Sneeze guards have been in use in restaurants for decades. With the rise of the COVID-19 pandemic, sneeze guards have been installed in public places like offices, schools and retail stores to reduce the risk of infection through respiratory droplets.

<span class="mw-page-title-main">Respiratory droplet</span> Type of particle formed by breathing

A respiratory droplet is a small aqueous droplet produced by exhalation, consisting of saliva or mucus and other matter derived from respiratory tract surfaces. Respiratory droplets are produced naturally as a result of breathing, speaking, sneezing, coughing, or vomiting, so they are always present in our breath, but speaking and coughing increase their number.

<span class="mw-page-title-main">N95 respirator</span> Particulate respirator meeting the N95 standard

An N95 filtering facepiece respirator, commonly abbreviated N95 respirator, is a particulate-filtering facepiece respirator that meets the U.S. National Institute for Occupational Safety and Health (NIOSH) N95 classification of air filtration, meaning that it filters at least 95% of airborne particles that have a mass median aerodynamic diameter of 0.3 micrometers. This standard does not require that the respirator be resistant to oil; another standard, P95, adds that requirement. The N95 type is the most common particulate-filtering facepiece respirator. It is an example of a mechanical filter respirator, which provides protection against particulates but not against gases or vapors. An authentic N95 respirator is marked with the text "NIOSH" or the NIOSH logo, the filter class ("N95"), a "TC" approval number of the form XXX-XXXX, the approval number must be listed on the NIOSH Certified Equipment List (CEL) or the NIOSH Trusted-Source page, and it must have headbands instead of ear loops.

<span class="mw-page-title-main">Workplace hazard controls for COVID-19</span> Prevention measures for COVID-19

Hazard controls for COVID-19 in workplaces are the application of occupational safety and health methodologies for hazard controls to the prevention of COVID-19. Vaccination is the most effective way to protect against severe illness or death from COVID-19. Multiple layers of controls are recommended, including measures such as remote work and flextime, increased ventilation, personal protective equipment (PPE) and face coverings, social distancing, and enhanced cleaning programs.

<span class="mw-page-title-main">Cloth face mask</span> Mask made of common textiles worn over the mouth and nose

A cloth face mask is a mask made of common textiles, usually cotton, worn over the mouth and nose. When more effective masks are not available, and when physical distancing is impossible, cloth face masks are recommended by public health agencies for disease "source control" in epidemic situations to protect others from virus laden droplets in infected mask wearers' breath, coughs, and sneezes. Because they are less effective than N95 masks, surgical masks, or physical distancing in protecting the wearer against viruses, they are not considered to be personal protective equipment by public health agencies. They are used by the general public in household and community settings as protection against both infectious diseases and particulate air pollution.

<span class="mw-page-title-main">Mechanical filter (respirator)</span> Air-filtering face masks or mask attachments

Mechanical filters are a class of filter for air-purifying respirators that mechanically stops particulates from reaching the wearer's nose and mouth. They come in multiple physical forms.

<span class="mw-page-title-main">Face masks during the COVID-19 pandemic</span> Health control procedure against COVID-19

During the COVID-19 pandemic, face masks or coverings, including N95, FFP2, surgical, and cloth masks, have been employed as public and personal health control measures against the spread of SARS-CoV-2, the virus that causes COVID-19.

In epidemiology, a non-pharmacological intervention (NPI) is any method used to reduce the spread of an epidemic disease without requiring pharmacological drug treatments. Examples of non-pharmacological interventions that reduce the spread of infectious diseases include wearing a face mask and staying away from sick people.

<span class="mw-page-title-main">Transmission of COVID-19</span> Mechanisms that spread coronavirus disease 2019

The transmission of COVID-19 is the passing of coronavirus disease 2019 from person to person. COVID-19 is mainly transmitted when people breathe in air contaminated by droplets/aerosols and small airborne particles containing the virus. Infected people exhale those particles as they breathe, talk, cough, sneeze, or sing. Transmission is more likely the closer people are. However, infection can occur over longer distances, particularly indoors.

FFP standards refer to the filtering half mask classification by EN 149, a European standard of testing and marking requirements for filtering half masks. FFP standard masks cover the nose, mouth and chin and may have inhalation and/or exhalation valves.

Nicole M. Bouvier is an American physician who is Professor of Medicine at Icahn School of Medicine at Mount Sinai. Her research considers the environmental and viral factors that impact respiratory transmission of influenza viruses.

References

  1. 1 2 3 "FAQs on the Emergency Use Authorization for Face Masks (Non-Surgical)". U.S. Food and Drug Administration . 2020-04-26. Retrieved 2020-05-21.
  2. Naunheim, Matthew R.; Bock, Jonathan; Doucette, Philip A.; Hoch, Matthew; Howell, Ian; Johns, Michael M.; Johnson, Aaron M.; Krishna, Priya; Meyer, David; Milstein, Claudio F.; Nix, John (2020-06-28). "Safer Singing During the SARS-CoV-2 Pandemic: What We Know and What We Don't". Journal of Voice. 35 (5): 765–771. doi:10.1016/j.jvoice.2020.06.028. ISSN   0892-1997. PMC   7330568 . PMID   32753296.
  3. 1 2 3 4 5 6 "Using face masks in the community - Reducing COVID-19 transmission from potentially asymptomatic or pre-symptomatic people through the use of face masks". European Centre for Disease Prevention and Control . 2020-04-08. Retrieved 2020-05-21.
  4. 1 2 3 4 5 6 7 "Interim Infection Prevention and Control Recommendations for Patients with Suspected or Confirmed Coronavirus Disease 2019 (COVID-19) in Healthcare Settings". U.S. Centers for Disease Control and Prevention . 2020-05-18. Retrieved 2020-05-21.
  5. 1 2 Hunziker, Patrick (2020-12-16). "Minimizing exposure to respiratory droplets, 'jet riders' and aerosols in air-conditioned hospital rooms by a 'Shield-and-Sink' strategy". medRxiv   10.1101/2020.12.08.20233056v1 .
  6. 1 2 3 Sommerstein, R; Fux, CA; Vuichard-Gysin, D; Abbas, M; Marschall, J; Balmelli, C; Troillet, N; Harbarth, S; Schlegel, M; Widmer, A; Swissnoso. (6 July 2020). "Risk of SARS-CoV-2 transmission by aerosols, the rational use of masks, and protection of healthcare workers from COVID-19". Antimicrobial Resistance and Infection Control. 9 (1): 100. doi: 10.1186/s13756-020-00763-0 . ISSN   2047-2994. PMC   7336106 . PMID   32631450.
  7. Carbone, Michele; Lednicky, John; Xiao, Shu-Yuan; Venditti, Mario; Bucci, Enrico (2021). "Coronavirus 2019 Infectious Disease Epidemic: Where We Are, What Can be Done and Hope for". Journal of Thoracic Oncology. 16 (Carbone M, Lednicky J, Xiao SY, Venditti M, Bucci E. Coronavirus 2019 Infectious Disease Epidemic: Where We Are, What Can Be Done and Hope For. J Thorac Oncol. 2021 Apr, 16(4):546-571. doi: 10.1016/j.jtho.2020.12.014. Epub 2021 Jan 7. PMID 33422679, PMCID: PMC7832772): 546–571. doi:10.1016/j.jtho.2020.12.014. PMC   7832772 . PMID   33422679.
  8. Tang, JW; Nicolle, AD; Pantelic, J; Jiang, M; Sekhr, C; Cheong, DK; Tham, KW (2011). "Qualitative real-time schlieren and shadowgraph imaging of human exhaled airflows: an aid to aerosol infection control". PLOS ONE. 6 (6): e21392. Bibcode:2011PLoSO...621392T. doi: 10.1371/journal.pone.0021392 . PMC   3120871 . PMID   21731730. (see video on Wikimedia Commons)
  9. 1 2 3 "Meat and Poultry Processing Workers and Employers: Interim Guidance from CDC and the Occupational Safety and Health Administration (OSHA)". Centers for Disease Control and Prevention. 2020-05-12. At section "Cloth face coverings in meat and poultry processing facilities". Retrieved 2020-05-24.
  10. Rengasamy S, Eimer B, Shaffer RE (2010). "Simple Respiratory Protection—Evaluation of the Filtration Performance of Cloth Masks and Common Fabric Materials Against 20–1000 nm Size Particles". Annals of Occupational Hygiene. Oxford University Press. 54 (7): 789–798. doi: 10.1093/annhyg/meq044 . ISSN   0003-4878. PMC   7314261 . PMID   20584862. The results showed that cloth masks and other fabric materials tested in the study had 40–90% instantaneous penetration levels against polydisperse NaCl aerosols employed in the National Institute for Occupational Safety and Health particulate respirator test protocol at 5.5 cm s−1.
  11. 1 2 "N95 Respirators and Surgical Masks (Face Masks)". U.S. Food and Drug Administration. 2020-04-05. Retrieved 2020-05-23.
  12. Robertson, Paddy (15 March 2020). "Comparison of Mask Standards, Ratings, and Filtration Effectiveness". Smart Air Filters.
  13. 中华人民共和国医药行业标准:YY 0469–2011 医用外科口罩 (Surgical mask) (in Chinese)
  14. 中华人民共和国医药行业标准:YY/T 0969–2013 一次性使用医用口罩 (Single-use medical face mask) Archived 2021-02-25 at the Wayback Machine (in Chinese)
  15. "Interim Infection Prevention and Control Recommendations for Patients with Suspected or Confirmed Coronavirus Disease 2019 (COVID-19) in Healthcare Settings". U.S. Centers for Disease Control and Prevention . 2020-05-18. Retrieved 2020-05-21.
  16. "Strategies for Optimizing the Supply of N95 Respirators". U.S. Centers for Disease Control and Prevention. 2020-04-02. At section "Prioritize the use of N95 respirators and facemasks by activity type". Retrieved 2020-05-21.