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Unless you’ve been living under a rock since 2020, you now know the value and importance of understanding how diseases spread from person to person. With more focus than ever being put on the origins of infection, it’s time that business owners educate themselves on how they can better protect their employees, customers, and themselves. What Is Epidemiology?Put simply – Epidemiology is the study of adverse health events as they take place within certain areas and certain populations. Specifically, it is a scientific discipline that focuses on where different diseases come from, how they spread, and how they can be controlled and contained. Of course, such a study has a number of implications for public health, including for groups as large as an entire city population and as small as a single office building. The Epidemiologic TriangleThe Epidemiologic Triangle is a chart that scientists and other researchers can use to evaluate different diseases and follow their progression. As you might have guessed, the chart has three specific parts outlining how diseases spread. They are:
Each disease will demonstrate its own unique interaction between these three different factors. For instance, the agent (typically the pathogen or parasite) is the item causing the infection or pandemic. However, it is subject to a variety of factors that ultimately determine whether becoming exposed to this agent will result in a person becoming ill. The host is the organism that is being exposed to the agent and is, therefore, susceptible to becoming ill (and going on to make others ill). There are countless factors affecting how this host may react to the agent, including their age, general hygiene, genetics, and overall health. Moreover, different combinations of agents and hosts will produce different results, such as asymptomatic and symptomatic. The Environment is the last part of the Epidemiologic Triangle. It is basically a term used to refer to any and all outside factors that could affect exposure or susceptibility. Examples include exposure to animals, climate changes, sanitation changes, and more. These factors are very difficult to identify at first and often become more evident as more hosts are studied. “Breaking” the TriangleThe reason it’s so important to understand the Epidemiologic Triangle is that it only takes the removal of one factor to break the cycle of infection. Common examples of how this is accomplished include:
Business owners can always encourage their employees and customers to take steps to prevent the spread of disease, but what really helps is hiring a full-time cleaning and sanitation crew like Windsor Building Services. As the leading commercial cleaning company in Greater Houston, we provide a wide range of services specifically designed to keep you, your employees, and your clients safe and healthy. In fact, our cleaning services were developed using best practices and procedures designed by the CDC for the specific purpose of breaking the Epidemiologic Triangle. So if you own a business in Spring, The Woodlands, Conroe, or any other Houston-area suburb, call Windsor Building Services today and invest in a better, healthier workspace. Anesth Analg. 2020 Jun 16 : 10.1213/ANE.0000000000005063. We read with great interest the important editorial by Orser1 that outlines recommendations for performing aerosol-generating medical procedures (AGMPs). The coronavirus disease 2019 (COVID-19) pandemic
places health care workers (HCWs) at high risk of exposure. As of April 2020, HCWs comprised 10% of the COVID-19 cases in Italy.2 We agree that extreme caution must be exercised and preventative strategies be usedwhen performing AGMPs, including tracheal intubation and manual ventilation, to minimize the risk of
transmission.1,3 This article broadens the current COVID-19 infectious control strategies through the concept of the epidemiological triad to further protect HCWs performing AGMPs. Snow,4 a pioneer anesthesiologist and father of modern epidemiology, first described the epidemiologic triad to trace the source of cholera outbreaks in London in the 1850s. The epidemiological triad (Figure) helps us understand the spread of diseases through 3components: agent, environment, and
host.4 In the context of COVID-19, the agentis the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), including the pathogenicity and virulence of various strains. The environmentrefers to extrinsic factors that affect the agentand opportunities for exposure like respiratory droplets and contaminated surfaces. The hostis any uninfected person and their individual susceptibility
characteristics (eg, age, sex, andcomorbidities). Minimizing the interactions between these components would reduce the spread of COVID-19. Epidemiological triad. A, The interrelationship of the 3 components: agent, environment, and host. B, The interrupting factors characterized into 3 scenarios: community, hospital, and AGMPs. AGMP indicates aerosol-generating medical procedure; AIIR, airborne infection isolation room; COVID-19, coronavirus disease 2019; HCW, health care worker; OR, xxx; PAPR, powered air purifying respirator; PPE, personal protective equipment; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2; UVGI, xxx. Factors that disrupt the proliferation of COVID-19 can be conceptualized into 3 scenarios (Figure): community, hospital, and AGMPs. “Interrupting factors” (IFs) between any 2components can be categorized as agent–hostIFs (decreasing the host’s susceptibility or diminishing the virus’ virulence), agent–environment IFs (eliminating or decreasing the viral burden in droplets and surfaces), and environment–host IFs (decreasing the opportunity for active virus to infect new hosts). AGENT–HOST IFsWhile a COVID-19 vaccine and/or treatment is the most effective agent–host IFs, they are still being developed. Thus, the focus should remain on promoting practical strategies that optimize environment–hostand agent–environmentIFs until a vaccine or treatment becomes available. ENVIRONMENT–HOST IFsEnvironment–hostIFs in the community include shelter-in-place policies and social distancing. Similarly, hospitals have implemented interim cancellations of elective surgical cases, restricted hospital visitors, and encouraged personal protective equipment (PPE) use. In both settings, frequent hand washing or disinfection, avoidance of physical contact, and restraint from touching one’s face have been vital to controlling the spread of COVID-19.3 During AGMPs, PPE (including N95 respirators, powered air purifying respirators [PAPRs], face shields, gowns, and gloves) remains the major environment–hostIF protecting HCWs. For AGMPs, such as intubation, video laryngoscopy provides slightly more distance between the infected patient and the HCW when compared to direct laryngoscopy, but the HCW still remains at high exposure risk. Although various innovative plastic barrier enclosure devices for performing AGMPs have been widely publicized,3 these barriers remain an exposure risk when removed or cleaned as the virus is temporarily contained rather than eliminated. Following the AGMP, HCWs must also remain cautious of exposed areas within the barrier, including the patient’s head, OR table, and the HCW’s own clothing, as infectious particles may settle on these surfaces. AGENT–ENVIRONMENT IFsAgent–environmentIFs in the community include the self-quarantine of infected individuals, respiratory hygiene, and mask wearing by infected individuals, and restriction of travel from areas with widespread ongoing transmission. In hospitals, airborne infection isolation rooms (AIIRs or negative pressure rooms) and dedicated hospital wards with devoted COVID health care teams limit transmission to the rest of the hospital. Despite these isolation measures, extensive contamination of environmental surfaces isfound in the rooms of COVID-19 patients.3 Because SARS-CoV-2 can persist on inanimate surfaces for up to 9 days, surface decontamination with disinfectants is an essential agent–environmentIF.3 Portable ultraviolet (UV)-light disinfection systems utilizing the germicidal properties of UVC (100–280 nm) irradiation have the added benefits of “no touch,” maintenance of a room’s ventilation, and lack of residue.3 Given the nature of AGMPs, implementation of agent–environmentIFs is challenging. The infected patient cannot be isolated from the HCW nor can the patient’s body be chemical disinfected or irradiated. High-efficiency particulate air (HEPA) filters on ventilator circuits have been usedbut are only useful in continuity with the patient’s airway. A facemask on the patient can decrease the aerosolization of SARS-CoV-2 into the environment but hinders performance of the AGMP. Performing an AGMP in an AIIR or negative pressure OR protects only HCWs outside of the room. Although AIIRs require a minimum of 12 air-flow changes per hour (ACH) and ORs require a minimum of 15 ACH,3 the viral particles are recirculated rather than refreshed resulting in increased exposure risks to the HCWs within the room. In fact, the Anesthesia Patient Safety Foundation (APSF) and the American Society of Anesthesiologists (ASA) recommend decontamination of the OR after care of COVID patients and “entry should be delayed until sufficient time has elapsed for enough air changes to remove aerosolized infectious particles.”3 Safety practices usedby other occupations exposed to hazardous particulates provide a great resource for alternative agent–environmentIFs for HCWs performing AGMPs. Local exhaust ventilation hoods near the contamination source provide effective control of dust and fumes generated in industries utilizing woodworking and soldering. Recently, a similar evacuation system for AGMPs was described.5 A commercially available, disposable oxygen face tent was repurposed and connected to a high-efficiency waste management system with a HEPA filter to form an aerosol evacuation system. Although clinical studies have not been performed, this evacuation system for AGMPs is encouraging becauseit is grounded in the same technology used by other high-risk occupations exposed to hazardous particulate matter. As the world begins to relax its protective interventions, we must “beware of the second wave of COVID-19.”6 The epidemiological triad provides a framework to decrease the spread of COVID-19 by strengthening currently usedIFs and refocusing innovative developments to address underutilized IFs without increasing exposure risks to HCWs. Ban C. H. Tsui, MD, MSC, FRCPC REFERENCES1. Orser BA. Recommendations for endotracheal intubation of COVID-19 patients. Anesth Analg. 2020;130:1109–1110. [PMC free article] [PubMed] [Google Scholar] 2. Chirico F, Nucera G, Magnavita N. COVID-19: protecting healthcare workers is a priority. Infect Control Hosp Epidemiol. 2020. [Epub ahead of print]. [PMC free article] [PubMed] [Google Scholar] 4. Snow J. Interview. John Snow interviewed by Kenneth J. Rothman. Epidemiology. 2004;15:641–644. [PubMed] [Google Scholar] 5. Tsui BCH. Re-purposing a face tent as a disposable aerosol evacuation system to reduce contamination in COVID-19 patients: a simulated demonstration. Can J Anaesth. 2020. [Epub ahead of print]. [PMC free article] [PubMed] [Google Scholar] Why is it important to understand infectious diseases?Human infection studies can help us: better understand how long immunity lasts for, and the impact of different Covid-19 strains on our immune system. test whether approved vaccines and treatments are effective against new strains.
Why is it important to be aware of how infectious diseases are spread?Some germs are helpful and even help us to stay healthy, while others are harmful and cause infection. By understanding about how people can catch an infectious disease, you can then take effective action to prevent their spread.
What is the purpose of the epidemiology triangle?The Epidemiologic Triangle The Epidemiologic Triangle is a model that scientists have developed for studying health problems. It can help your students understand infectious diseases and how they spread.
When using the epidemiological triangle model to identify causation transmission and risks related to infectious diseases which factor represents the host?First epidemiologists have to identify the three vertices of the triangle: Agent: A type of virus called a coronavirus, identified as SARS-CoV-2. Host: Humans, especially those with comorbidities, and older adults. Environment: SARS-CoV-2 spreads through droplets in the air and on surfaces.
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Why is the triangle important to understanding the spread of infectious diseases?
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