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Wells-Riley Model
The Wells-Riley model is a simple model of the airborne transmission of infectious diseases, developed by William F. Wells and Richard L. Riley for tuberculosis and measles. Wells-Riley can also be applied to other diseases transmitted in the air, such as COVID-19. The model describes the situation where one or more infected people are sharing a room (and so the room air) with other people who are susceptible to infection. It makes predictions for the probability that a susceptible person becomes infected. The prediction is that infection is more likely for small poorly ventilated rooms, and if the infected person is highly infectious. The Wells-Riley is a highly simplified model of a very complex process, but does at least make predictions for how the probability of infection varies with things within our control, such as room ventilation. Description of model Wells-Riley assumes that the air contains doses of the infectious bacterium or virus, and that you become infected if ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Airborne Transmission
Airborne 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. Aerosol transmission has traditionally been considered distinct from transmission by droplets, but this distinction is no longer used. Respiratory droplets were thought to rapidly fall to the ground after emission: but smaller droplets and aerosols also contain live infectious agents, and can remain in the air longer and travel farther. Individu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Attack Rate
In epidemiology, the attack rate is the proportion of an at-risk population that contracts the disease during a specified time interval. It is used in hypothetical predictions and during actual outbreaks of disease. An at-risk population is defined as one that has no immunity to the attacking pathogen which can be either a novel pathogen or an established pathogen. It is used to project the number of infections to expect during an epidemic. This aids in marshalling resources for delivery of medical care as well as production of vaccines and/or anti-viral and anti-bacterial medicines.Anthony N. Glaser. High-Yield Biostatistics. Williams & Wilkins. Baltimore. 1995 The rate is arrived at by taking the number of new cases in the population at risk and dividing by the number of persons at risk in the population. See also *Incidence (epidemiology) *Compartmental models in epidemiology *Herd immunity Herd immunity (also called herd effect, community immunity, population immunity, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
National Geographic
''National Geographic'' (formerly the ''National Geographic Magazine'', sometimes branded as NAT GEO) is a popular American monthly magazine published by National Geographic Partners. Known for its photojournalism, it is one of the most widely read magazines of all time. The magazine was founded in 1888 as a scholarly journal, nine months after the establishment of the society, but is now a popular magazine. In 1905, it began including pictures, a style for which it became well-known. Its first color photos appeared in the 1910s. During the Cold War, the magazine committed itself to present a balanced view of the physical and human geography of countries beyond the Iron Curtain. Later, the magazine became outspoken on environmental issues. Since 2019, controlling interest has been held by The Walt Disney Company. Topics of features generally concern geography, history, nature, science, and world culture. The magazine is well known for its distinctive appearance: a thick squa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Google Sheets
Google Sheets is a spreadsheet program included as part of the free, web-based Google Docs Editors suite offered by Google. The service also includes: Google Docs, Google Slides, Google Drawings, Google Forms, Google Sites and Google Keep. Google Sheets is available as a web application, mobile app for: Android, iOS, Microsoft Windows, BlackBerry OS and as a desktop application on Google's ChromeOS. The app is compatible with Microsoft Excel file formats. The app allows users to create and edit files online while collaborating with other users in real-time. Edits are tracked by a user with a revision history presenting changes. An editor's position is highlighted with an editor-specific color and cursor and a permissions system regulates what users can do. Updates have introduced features using machine learning, including "Explore", offering answers based on natural language questions in a spreadsheet. History Google Sheets originated from XL2Web, a web-based spreadsheet appl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Skagit County, Washington
Skagit County is a county in the U.S. state of Washington. As of the 2020 census, the population was 129,523. The county seat and largest city is Mount Vernon. The county was formed in 1883 from Whatcom County and is named for the Skagit Indian tribe, which has been indigenous to the area prior to European-American settlement. Skagit County comprises the Mount Vernon- Anacortes, WA Metropolitan Statistical Area, and is included in the Seattle- Tacoma, WA Combined Statistical Area. It is located in the Puget Sound region. Geography According to the United States Census Bureau, the county has a total area of , of which is land and (9.8%) is water. It is noted for its broad, fertile valley of the Skagit River, a center for cultivation of tulips and strawberries. Geographic features * Allan Island *Burrows Island *Cascade Mountains *Cypress Island * Fir Island *Fidalgo Island *Guemes Island * Hart Island * Hope Island *Kiket Island *Pass Island *Samish Island * Sauk River ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Superspreading Event
A superspreading event (SSEV) is an event in which an infectious disease is spread much more than usual, while an unusually contagious organism infected with a disease is known as a superspreader. In the context of a human-borne illness, a superspreader is an individual who is more likely to infect others, compared with a typical infected person. Such superspreaders are of particular concern in epidemiology. Some cases of superspreading conform to the 80/20 rule, where approximately 20% of infected individuals are responsible for 80% of transmissions, although superspreading can still be said to occur when superspreaders account for a higher or lower percentage of transmissions. In epidemics with such superspreader events, the majority of individuals infect relatively few secondary contacts. SSEVs are shaped by multiple factors including a decline in herd immunity, nosocomial infections, virulence, viral load, misdiagnosis, airflow dynamics, immune suppression, and co-infect ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transmission Of COVID-19
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 more physically close people are. However, infection can occur over longer distances, particularly indoors. Infectivity can begin four to five days before the onset of symptoms, although contact tracing typically begins only two to three days before symptom onset. Infected people can spread the disease even if they are pre-symptomatic or asymptomatic. Most commonly, the peak viral load in upper respiratory tract samples occurs close to the time of symptom onset and declines after the first week after symptoms begin. Current evidence suggests a duration of viral shedding and the period of infectiousness of up to ten days follo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Air Changes Per Hour
Air changes per hour, abbreviated ACPH or ACH, or air change rate is the number of times that the total air volume in a room or space is completely removed and replaced in an hour. If the air in the space is either uniform or perfectly mixed, air changes per hour is a measure of how many times the air within a defined space is replaced each hour. Perfectly mixed air refers to a theoretical condition where supply air is instantly and uniformly mixed with the air already present in a space, so that conditions such as age of air and concentration of pollutants are spatially uniform. In many air distribution arrangements, air is neither uniform nor perfectly mixed. The actual percentage of an enclosure's air which is exchanged in a period depends on the airflow efficiency of the enclosure and the methods used to ventilate it. These systems range from a conceptual system of perfect displacement, which removes and replaces all air in a space, to a short circuit flow in which very little o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Filtration
Filtration is a physical separation process that separates solid matter and fluid from a mixture using a ''filter medium'' that has a complex structure through which only the fluid can pass. Solid particles that cannot pass through the filter medium are described as ''oversize'' and the fluid that passes through is called the ''filtrate''. Oversize particles may form a filter cake on top of the filter and may also block the filter lattice, preventing the fluid phase from crossing the filter, known as ''blinding''. The size of the largest particles that can successfully pass through a filter is called the effective ''pore size'' of that filter. The separation of solid and fluid is imperfect; solids will be contaminated with some fluid and filtrate will contain fine particles (depending on the pore size, filter thickness and biological activity). Filtration occurs both in nature and in engineered systems; there are biological, geological, and industrial forms. Filtration is als ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Virus
A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Since Dmitri Ivanovsky's 1892 article describing a non-bacterial pathogen infecting tobacco plants and the discovery of the tobacco mosaic virus by Martinus Beijerinck in 1898,Dimmock p. 4 more than 9,000 virus species have been described in detail of the millions of types of viruses in the environment. Viruses are found in almost every ecosystem on Earth and are the most numerous type of biological entity. The study of viruses is known as virology, a subspeciality of microbiology. When infected, a host cell is often forced to rapidly produce thousands of copies of the original virus. When not inside an infected cell or in the process of infecting a cell, viruses exist in the form of independent particles, or ''virions'', consisting of (i) the genetic material, i. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Infectious Agent
In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ. The term ''pathogen'' came into use in the 1880s. Typically, the term ''pathogen'' is used to describe an ''infectious'' microorganism or agent, such as a virus, bacterium, protozoan, prion, viroid, or fungus. Small animals, such as helminths and insects, can also cause or transmit disease. However, these animals are usually referred to as parasites rather than pathogens. The scientific study of microscopic organisms, including microscopic pathogenic organisms, is called microbiology, while parasitology refers to the scientific study of parasites and the organisms that host them. There are several pathways through which pathogens can invade a host. The principal pathways have different episodic time frames, but soil has the longest or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sneeze
A sneeze (also known as sternutation) is a semi-autonomous, convulsive expulsion of air from the lungs through the nose and mouth, usually caused by foreign particles irritating the nasal mucosa. A sneeze expels air forcibly from the mouth and nose in an explosive, spasmodic involuntary action. This action allows for mucus to escape through the nasal cavity. Sneezing is possibly linked to sudden exposure to bright light, sudden change (fall) in temperature, breeze of cold air, a particularly full stomach, exposure to allergens, or viral infection. Because sneezes can spread disease through infectious aerosol droplets, it is recommended to cover one's mouth and nose with the forearm, the inside of the elbow, a tissue or a handkerchief while sneezing. In addition to covering the mouth, looking down is also recommended in order to change the direction of the droplets spread and avoid high concentration in the human breathing heights. The function of sneezing is to expel mucus con ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
