This is a collection of free full-text PMC articles about COVID transmission by aerosols:
The practice of social distancing and wearing masks has been popular worldwide in combating the contraction of COVID-19.
Undeniably, although such practices help control the COVID-19 pandemic to a greater extent, the complete control of virus-laden droplet and aerosol transmission by such practices is poorly understood.
This review paper intends to outline the literature concerning the transmission of virus-laden droplets and aerosols in different environmental settings and demonstrates the behavior of droplets and aerosols resulted from a cough-jet of an infected person in various confined spaces.
The case studies that have come out in different countries have, with prima facie evidence, manifested that the airborne transmission plays a profound role in contracting susceptible hosts.
The infection propensities in confined spaces (airplane, passenger car, and healthcare center) by the transmission of droplets and aerosols under varying ventilation conditions were discussed.
In the context of Coronavirus Disease (2019) (COVID-19) cases globally, there is a lack of consensus across cultures on whether wearing face masks is an effective physical intervention against disease transmission.
1) illustrates transmission routes of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2);
2) addresses controversies surrounding the mask from perspectives of attitude, effectiveness, and necessity of wearing the mask with evidence that the use of mask would effectively interrupt the transmission of infectious diseases in both hospital settings and community settings; and
3) provides suggestion that the public should wear the mask during COVID-19 pandemic according to local context.
To achieve this goal, government should establish a risk adjusted strategy of mask use to scientifically publicize the use of masks, guarantee sufficient supply of masks, and cooperate for reducing health resources inequities.
Airborne route and bad use of ventilation systems as non-negligible factors in SARS-CoV-2 transmission – Med Hypotheses. 2020 Aug;
The world is facing a pandemic of unseen proportions caused by a corona virus named SARS-CoV-2 with unprecedent worldwide measures being taken to tackle its contagion.
Person-to-person transmission is accepted but WHO only considers aerosol transmission when procedures or support treatments that produce aerosol are performed.
Transmission mechanisms are not fully understood and there is evidence for an airborne route to be considered, as the virus remains viable in aerosols for at least 3 h and that mask usage was the best intervention to prevent infection.
Heating, Ventilation and Air Conditioning Systems (HVAC) are used as a primary infection disease control measure. However, if not correctly used, they may contribute to the transmission/spreading of airborne diseases as proposed in the past for SARS.
The authors believe that airborne transmission is possible and that HVAC systems when not adequately used may contribute to the transmission of the virus, as suggested by descriptions from Japan, Germany, and the Diamond Princess Cruise Ship. Previous SARS outbreaks reported at Amoy Gardens, Emergency Rooms and Hotels, also suggested an airborne transmission.
Further studies are warranted to confirm our hypotheses but the assumption of such way of transmission would cause a major shift in measures recommended to prevent infection such as the disseminated use of masks and structural changes to hospital and other facilities with HVAC systems.
The transmission efficiency of SARS-CoV-2 has proved to be high, with reported reproductive numbers greater than that of the 2009 H1N1 influenza virus
The routes of exposure that have led to this high transmissivity have been the subject of considerable discussion, notably the contribution of aerosol transmission.
As with any infectious respiratory disease, an infected individual can release aerosols and droplets containing SARS-CoV-2 by coughing or sneezing
Similar to what we know about influenza A and B, MERS-CoV, and SARS-CoV-1, these virus-containing aerosols and droplets can lead to short-range airborne transmission (~ 6 ft)
Such aerosols (< 10-μm diameter) and droplets (> 10-μm diameter) can promote infection through
(i) deposition on surfaces and subsequent hand-to-mouth/nose/eye transfer and
While suspended airborne droplets can persist in the air for several minutes, the smaller aerosols do not rapidly settle and can persist for longer durations (~ minutes to hours).
Once airborne, the characteristics of aerosols generated by cough or sneeze are dynamic, notably decreasing in size due to evaporative loss of water depending on ambient humidity and temperature levels
As the size of aerosols decrease, their ability to disperse in the air is enhanced. Therefore, inhalation of aerosol-borne SARS-CoV-2 is likely to be a relevant mode of viral infection, with the range of aerosol transmission extending beyond 6 ft of an infected individual.
Disease transmission by SARS-CoV-2 aerosols
The premise of aerosol transmission necessitates that the virus remains viable in the air. As viability decreases over time, it is important to understand the rate of inactivation under different environmental conditions, e.g., temperature and humidity
Viability of SARS-CoV-2 in aerosol collected from real-world air samples, however, has not yet been fully explored.
Detection of SARS-CoV-2 in the air prompts questions about safe exposure levels.
The high transmissivity of the virus suggests that a low dose might be sufficient to infect an individual; however, such studies have yet to evaluate the infectious dose of SARS-CoV-2.
Until scientific evidence emerges, it is useful for individuals to follow approaches that minimize their risk of infection by reducing their exposure level and duration of exposure.
Initial studies (as detailed above) report a range of airborne virus exposure levels in hospitals, as well as public spaces.
The combined use of masks and physical distancing can be effective approaches for decreasing exposure to airborne forms of SARS-CoV-2.
Avoiding or minimizing the time in contact with these potential aerosol exposures would also be a critical parameter in lowering risk.
Preventing new infections
An inherent difficulty associated with the airborne route of transmission is that the measures used to reduce airborne exposure can be laborious and are not fail-proof.
Common approaches for mitigating airborne exposures include
(i) identification of emission sources,
(ii) prevention of viral shedding and inhalation exposure, and
(iii) environmental controls.
The topic of environmental controls leverages evidence of reduced exposures by improving ventilation, utilization of portable filtration devices], or other aerosol inactivation technologies, and cleaning practices to reduce exposure from resuspension.
The risk of newly emerging diseases is constantly present in a world where changes occur significantly in climatic, commercial, and ecological conditions, in addition to the development of biomedical investigations in new situations. An epidemic respiratory disease instigated by a new coronavirus was initially identified in and has resulted in the current global dissemination.
present article, therefore, describes the SARS-CoV-2 paths of contagion such as drinking water, solid waste, sewer water, ambient air, and the rest of emerging likely paths.
In humans, coronaviruses fall into the range of viruses causing the common cold and also more serious respiratory diseases, specially, severe acute respiratory syndrome (SARS, 2002) and the Middle East respiratory syndrome (MERS, 2014), both of which are zoonotic diseases initially detected by the culture of viruses from patients with common colds in the mid-1960s
1.2. Diseases caused by coronaviruses
Among the seven subtypes of coronaviruses capable of infecting humans, beta-coronaviruses can possibly induce serious disease and mortalities.
1.3. The transmission routes
Due to the relationship of the SARS-CoV-2 to the genus betacoronavirus, the diseases and transmission paths for the genus are depicted in Fig. 1 .
Research suggests that SARS-CoV-2 is probably air-transmitted via aerosols.
2. Environmental transmission possibility
3. New ways of SARS-CoV-2 transmission that maybe facilitated by angiotensin-converting enzyme 2 (ACE2)
These observations revealed that the organs with high ACE2-expressing cells would be regarded as those with high potential risk for SARS-CoV-2 contamination
Consideration of the Aerosol Transmission for COVID‐19 and Public Health – Risk Anal. 2020 May
This article analyzes the available evidence to address airborne, aerosol transmission of the SARS‐CoV‐2.
We review and present three lines of evidence: case reports of transmission for asymptomatic individuals in association with studies that show that normal breathing and talking produce predominantly small droplets of the size that are subject to aerosol transport; limited empirical data that have recorded aerosolized SARS‐CoV‐2 particles that remain suspended in the air for hours and are subject to transport over distances including outside of rooms and intrabuilding, and the broader literature that further supports the importance of aerosol transmission of infectious diseases.
The weight of the available evidence warrants immediate attention to address the significance of aerosols and implications for public health protection.
Aerosol-Transmitted Infections—a New Consideration for Public Health and Infection Control Teams – Curr Treat Options Infect Dis. 2015;
Since the emergence of the 2003 severe acute respiratory syndrome (SARS), the 2003 reemergence of avian A/H5N1, the emergence of the 2009 pandemic influenza A/H1N1, the 2012 emergence of Middle East respiratory syndrome (MERS), the 2013 emergence of avian A/H7N9 and the 2014 Ebola virus outbreaks,
the potential for the aerosol transmission of infectious agents is now routinely considered in the investigation of any outbreak.
Although many organisms have traditionally been considered to be transmitted by only one route (e.g. direct/indirect contact and/or faecal-orally), it is now apparent that the aerosol transmission route is also possible and opportunistic, depending on any potentially aerosol-generating procedures, the severity of illness and the degree and duration of pathogen-shedding in the infected patient, as well as the environment in which these activities are conducted.
This article reviews the evidence and characteristics of some of the accepted (tuberculosis, measles, chickenpox, whooping cough) and some of the more opportunistic (influenza, Clostridium difficile, norovirus) aerosol-transmitted infectious agents and outlines methods of detecting and quantifying transmission.