In addition, numerous Gram-positive bacteria are usually disseminated from the skin, oral and nasal surfaces, and hair of humans. Infected individuals can spread pathogenic bacilli when coughing, talking, speaking, laughing, and sneezing. For bacteria, Mycobacterium tuberculosis is recognized for its role as the causative agent of human tuberculosis and responsible for previous outbreaks. Other viruses share similar properties in terms of stability and dispersity in the air environment such as the Influenza virus, Norovirus, MRES and SARS-COV-1 viruses. It was shown in the literature that SARS-CoV-2 has the ability to disperse from patients to ward vent openings, and its viral RNA was detected in ventilation exhaust filters located at least 50 m from patient room vent openings. The most recent example is the spread of SARS-CoV-2 in the air that caused global outbreaks in different settings during the current pandemic. airborne infections), and can result in large clusters of infection in a short period. A World Health Organization review of the evidence published in 2009 stated that viral infectious diseases can be transmitted across distances relevant to indoor environments by aerosols (i.e. Aggregates of biological material also afford protection from environmental stresses such as desiccation, and exposure to ultraviolet radiation ozone and other pollutants in the atmosphere. The larger aggregates have different aerodynamic properties than single-cell units therefore their dispersal may be different than single-unit particles. These microorganisms can be dispersed in the air as single units but are often present as aggregate formations. Virus particles are nanometer in size and vary from 20nm to 500nm, bacterial cells are approximately 1 µm in diameter, and fungal spores are >1 µm. The individual particle size of particulate material in bioaerosols is generally 0.3–100 µm in diameter larger particles tend to settle rapidly and are not readily transported in the air. Talking and coughing generate bioaerosols from individuals, some of which may be infectious. The lung is more susceptible to infection than the gastrointestinal tract as ingested microorganisms must pass through the acidic environment of the stomach before they can colonise tissue, while inhaled microorganisms are deposited directly on the moist surfaces of the respiratory tract. As we know, inhalation exposes the upper and lower respiratory tracts of humans to a variety of airborne particles and vapours. This airborne transmission becomes even more prevalent in healthcare settings because of overburdened hospitals and the presence of immunosuppressed patients. Therefore, in this article, we will discuss in more detail the major routes of transmission and give an overall overview of the spread of a wide range of pathogenic microorganisms.Įxposure of human beings to different airborne pathogens has resulted in the emergence of epidemics of respiratory infections. and Actinobacter baumannii.ĭuring the search process, not many published articles were found addressing all the routes and vectors of transmission and their relevant microorganisms. This is in addition to other microorganisms such as Staphylococcus aureus, Escherichia coli, Norovirus, Salmonella spp. However, some pathogens can have more than one route of transmission, as it was reported with the recent SARS-CoV-2 which showed stability as an aerosol, on surfaces and in water. Airborne pathogens are known to primarily cause but not limited to upper respiratory tract infections such as the common cold or pneumonia, whilst water-borne pathogens can cause gastroenteritis and other diarrhoeal infections. For example, an airborne pathogen can differ from a waterborne pathogen in terms of the disease or infection they cause and their survivability characteristics. It is very important to understand the differences within these routes and the differences among the pathogenic microorganisms for better infection control measures. These vectors including air, surfaces and water act as a bridge that transports the infectious agents directly or indirectly into humans or living organisms. The spread of pathogenic microorganisms can occur through different vectors of transmission.
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