Through an article published this month in the Journal of Physics Communications (IOPScience). Mexican researchers from the National Autonomous University of Mexico (UNAM) and the Potosino Institute for Scientific and Technological Research (IPICYT) have modeled the dynamics that salivary droplets or droplets loaded with SARS-CoV-2 they can take from 33 minutes to 3.83 days to fall.
What Mexican researchers are they?
Dr. Alipio Gustavo Calles Martínez, from the Faculty of Sciences of the UNAM, and Dr. José Luis Morán López, researcher from the Division of Advanced Materials of the IPICYT. They were tasked with creating a modeling of the viral load that is expelled in saliva droplets that carry SARS-CoV-2.
The size of the droplets influences their dynamics
In this model it is established that the time it takes to fall depends on the size of the aerosols. And, for the same reason, the risk of infection. From the calculations it is shown that it is extremely important to ventilate closed environments.
“With Dr. Alipio Calles we analyzed four size ranges that go from aerosols to drops. The 0.4–5 micron spray, the small one (5.1-10 microns). The medium (10.1–100 microns) and the large (100.1–450 microns) and we found that, in the aerosol regime. Friction forces quickly stop the drops in their horizontal motion. And they fall in an extreme way and slowly dragged downwards by the gravitational force ”. This is detailed by Dr. Emeritus of the National System of Researchers, SNI.
The time for the drops to fall varies
Explain that in a quiet environment, such as the living room at home, the time to fall ranges from 3.83 days to 33.3 min depending on whether they are droplets or aerosols.
Dr. Morán López explains that one of the routes that has been scientifically proven is that the transmission of COVID-19 is through droplets of saliva that infected people produce when they speak, cough or sneeze. Which increase the risk of infection in places with poor ventilation and with greater human conglomeration, for example, a meeting between several individuals in a living room with the windows closed.
The importance of the correct use of the mask
“Larger droplets take less time and hit the ground meters from the source, and according to the density of virus per milliliter, we estimate the amount expelled into the environment. Small and medium size drops contain the most. But since the aerosol droplets remain in the air for a longer time, they pose a high risk of infection. Hence the great importance of facial protection to minimize the transmission of COVID-19, with an efficient face mask that covers the mouth and nose ”, he explained.
On the other hand, the doctor in Theoretical Physics from the Free University of Berlin recalled that the WHO recommended people isolation, disinfecting their hands and social distancing as measures to avoid contracting COVID-19. It is even recently a matter of debate that the infection occurs by inhalation of small drops of saliva produced when talking, sneezing or coughing by infected people. Therefore, it has been shown to be a highly probable route of infection.
This dynamic has been verified by a recent study, in which high viral loads of SARS-CoV-2 were found in the oral fluids of patients suffering from coronavirus disease.
The results are consistent with other research
“We are aware that more than one way has been observed. But we hope that these singlemode curves represent the most important contributions in the aerosol regime. Our results are consistent with the experimental data reported on the flight time and travel distance of the saliva droplets ”, argued Dr. Morán.
In addition, he pointed out that the experiments carried out by epidemiologists and infectologists, to find the minimum number of virions necessary for a person to contract the infection, is a field of intensive research ”.
Research will stimulate sanitary measures
For the researchers, this model is a preview that their results will stimulate more droplet dynamics experiments. And they will allow health authorities to implement scientifically supported measures to reduce the transmission of the virus.
It should be noted that the work is dedicated to the memory of the Nobel Prize, Mario Molina, who made seminal contributions in the field and motivated them to carry out this important analysis.
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