Effects of temperature variation and humidity on the death of COVID-19 in Wuhan, China.

Correlation between weather and Covid-19 pandemic in Jakarta, Indonesia.

Viable SARS-CoV-2 in the air of a hospital room with COVID-19 patients.


 
 Summary
 The epidemics of severe acute respiratory syndrome (SARS) in 2003 highlighted both short- and long-range transmission routes, i.e. between infected patients and healthcare workers, and between distant locations. With other infections such as tuberculosis, measles and chickenpox, the concept of aerosol transmission is so well accepted that isolation of such patients is the norm. With current concerns about a possible approaching influenza pandemic, the control of transmission via infectious air has become more important. Therefore, the aim of this review is to describe the factors involved in: (1) the generation of an infectious aerosol, (2) the transmission of infectious droplets or droplet nuclei from this aerosol, and (3) the potential for inhalation of such droplets or droplet nuclei by a susceptible host. On this basis, recommendations are made to improve the control of aerosol-transmitted infections in hospitals as well as in the design and construction of future isolation facilities.
 


Iconographies supplémentaires de l'article : Factors involved in the aerosol transmission of infection and control of ventilation in healthcare premises

The current revival of the American economy is being predicated on social distancing, specifically the Six-Foot Rule, a guideline that offers little protection from pathogen-bearing aerosol droplets sufficiently small to be continuously mixed through an indoor space. The importance of airborne transmission of COVID-19 is now widely recognized. While tools for risk assessment have recently been developed, no safety guideline has been proposed to protect against it. We here build on models of airborne disease transmission in order to derive an indoor safety guideline that would impose an upper bound on the "cumulative exposure time," the product of the number of occupants and their time in an enclosed space. We demonstrate how this bound depends on the rates of ventilation and air filtration, dimensions of the room, breathing rate, respiratory activity and face mask use of its occupants, and infectiousness of the respiratory aerosols. By synthesizing available data from the best-characterized indoor spreading events with respiratory drop size distributions, we estimate an infectious dose on the order of 10 aerosol-borne virions. The new virus (severe acute respiratory syndrome coronavirus 2 [SARS-CoV-2]) is thus inferred to be an order of magnitude more infectious than its forerunner (SARS-CoV), consistent with the pandemic status achieved by COVID-19. Case studies are presented for classrooms and nursing homes, and a spreadsheet and online app are provided to facilitate use of our guideline. Implications for contact tracing and quarantining are considered, and appropriate caveats enumerated. Particular consideration is given to respiratory jets, which may substantially elevate risk when face masks are not worn.

https://www.pnas.org/content/pnas/118/17/e2018995118.full.pdf

A guideline to limit indoor airborne transmission of COVID-19.

Transmission of COVID-19 virus by droplets and aerosols: A critical review on the unresolved dichotomy.

Phthalates are widely used as a plasticizer in manufacturing polyethylene terephthalate (PET) bottles to improve softness, flexibility, durability, longevity, and workability. Phthalates are known in instigating profound human health hazards. In many developing countries, lack of proper disposal facilities established for empty PET bottles and the absence of legislation on reuse invariably persuade people to reuse them for storing potable water. An experiment was conducted with two commercial brands of PET bottles to explore the potential of phthalate migration when domestically refilled and reused in multiple times at two temperature conditions. Temperatures of ambient (27 ± 2 °C) and warm (60 ± 2 °C) were selected as the refilling temperatures because of the common practice by people. For both brands, only bis(2-ethylhexyl) phthalate (DEHP) levels were detected in refilled water in every event of reuse. For both brands, mean DEHP levels migrated to water at 60 ± 2 °C were significantly higher (p < 0.05) compared to those at 27 ± 2 °C. Risk analyses carried out on human health suggested that there exist no definite acute or chronic health risks when the refilled water is consumed continuously for 30 years for both temperatures. Still, such risks were higher for the consumption of refilled water of warm temperatures than those of ambient temperature. However, this study elucidates that DEHP migration would be at an alarming rate when the events of reuse of a single bottle increase so that regulations banning the reuse of empty PET bottles are paramount, especially for developing countries.

Migration of phthalates from PET water bottle in events of repeated uses and associated risk assessment

https://scholarworks.utrgv.edu/cgi/viewcontent.cgi?article=1480&context=pa_fac

Grappling with COVID-19 by imposing and lifting non-pharmaceutical interventions in Sri Lanka: A modeling perspective

The aim of the study is to identify the wood utilized in the traditional houses built in Uva province of Sri Lanka, constructed using traditional construction technologies. The timber samples were taken out from roof elements such as rafters, wall plates and reapers from three different timber structures located at three different locations constructed during 1960 – 1970 using vernacular timber preservation technics and preservatives. Samples were extracted and adequately prepared for a microscopic investigation to observe the characteristic microscopic anatomical features. Sledge microtome was used for wood sectioning and photomicrographs were obtained by polarized light microscope. The authentic samples and reference microscopic identification keys were employed in order to conclude on the wood species involved. The relative density of the samples was also measured using the maximum moisture content method to verify the identification. Timber samples were identified using vessels, fibers, rays, parenchyma, and other microscopic features. Based on the macro and micro examination of the external and microanatomical features the timber used for rafters, reapers, wall plates were identified as Mango wood which is scientifically known as Mangifera indica. The relative density values were in the range of 0.52 – 0.7.

Hasini Perera

Papers

Transmission of COVID-19 virus by droplets and aerosols: A critical review on the unresolved dichotomy.

Migration of phthalates from PET water bottle in events of repeated uses and associated risk assessment

Grappling with COVID-19 by imposing and lifting non-pharmaceutical interventions in Sri Lanka: A modeling perspective

Preliminary investigation on ancient timber structures through microscopic analysis