Scientists estimate the speed and distance of coronavirus transmission when people cough, sneeze, speak, and run

There are many scientists who know, and many who do not.

In “Coughs and Sneezes: Their Role in Transmission of Viral Respiratory Infections, Including SARS-CoV-2,” published Tuesday, the researchers describe the various types and sizes of virus-containing drops present in sneezes and coughs, and how some medical procedures and devices can spread these drops. “Coughing and sneezing create variable-sized respiratory drops that spread viral respiratory infections,” according to the article, published online in the American Journal of Respiratory and Critical Care Medicine by the American Thoracic Society.

“While most of the respiratory droplets leak through the nose or deposit in the oropharynx, the smaller nuclei of the droplets are suspended in the air in the room and can be inhaled by people further away from the patient.”

“Because these droplets are forcefully expelled, they disperse in the environment and can be exhaled by a susceptible host. While most respiratory droplets leak through the nose or deposit in the oropharynx, the smaller droplet nuclei are suspended in room air and can be inhaled by people furthest from the patient, ”said Rajiv Dhand, professor. and president of the Department of Medicine and associate. dean of clinical affairs at the University of Tennessee School of Medicine and co-author of the article.

Among the researchers’ recommendations: “Healthcare providers should stay six feet away from infected patients, especially when the patient coughs or sneezes. For spontaneously breathing patients, putting a surgical mask on the patient’s face or using handkerchiefs to cover their mouths, especially during coughs, sneezes, or conversation, can reduce the dispersal distance or viral load. Although ideally, infected patients should be in individual rooms to avoid dispersal of the drops, it is acceptable that two patients with the same infection that are spread by the respiratory drops are in the same room. “

Contagion of speech droplets

“Speech droplets generated by asymptomatic carriers of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are increasingly seen as a likely mode of disease transmission,” a separate study published in the latest issue of Proceedings. of the peer-reviewed National Academy of Sciences, the official journal of the National Academy of Sciences, found. “Highly sensitive laser light scattering observations have revealed that speaking aloud can emit thousands of drops of oral fluid per second.”

In a closed environment of stagnant air, the droplets disappear from view after eight to 14 minutes, “which corresponds to the nuclei of ac droplets. Diameter of 4um, or drops of 12um to 21um before dehydration,” they wrote. The researchers. One micrometer, um, is equivalent to one millionth of a meter. The coronavirus is 0.125 um. Scientists said that while it has long been recognized that respiratory viruses such as the coronavirus can be transmitted through droplets generated Coughing or sneezing is less well-known than normal speech as well.High viral loads of SARS-CoV-2 have been detected in oral fluids from COVID-19 positive patients, including asymptomatic ones.

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How far can coronavirus drops travel

Social distancing has been defined for people who sit still. “It does not account for possible aerodynamic effects introduced by a person’s movement, such as brisk walking, running, and biking,” the researchers wrote in another study titled, “Towards an Aerodynamically Equivalent COVID-19, Social Distance of 1, 5 meters for walking and running. “Bert Blocken, professor of civil engineering at Eindhoven University of Technology in the Netherlands and Katholieke Universiteit Leuven in Flanders, Belgium, and his co-authors recommend that people avoid walking or running in the slip of a walker or runner in the park and street. .

“In the absence of headwind, tailwind, and crosswind, for fast walking at 4 kilometers per hour, this distance is approximately 5 meters (16 feet) and for running at 14.4 kilometers per hour, this distance is approximately 10 meters (32 feet), ”found the study, which has not been peer-reviewed. The smaller the distance between runners, the greater the fraction of drops the final runner is exposed to. “If people want to run behind and / or overtake other walkers and runners with respect to social distance,” they can do it by moving out of the slip current into a step formation, “he added.

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Internal factors that contribute to contagion

Factors that affect whether the virus remains “stable” and contribute to transmission: humidity and room temperature, air conditioning, if there are open windows, general air quality, room size and, of course, how many people are present and how close they are to each other. “In contrast to SARS-CoV-1, the majority of secondary cases of new SARS-CoV-2 transmission appear to be occurring in community settings rather than healthcare settings,” found a recent study published in the New England Journal of Medicine.

The COVID-19 pandemic, which was first identified in Wuhan, China in December, had infected 9,154,232 people worldwide and 2,325,970 in the United States as of Tuesday. It had claimed at least 473,650 lives worldwide, 120,771 of which were in the United States. USA, According to the Johns Hopkins University Center for Systems Science and Engineering. The Dow Jones DJIA Industrial Index,
+ 0.50%
and the S&P 500 SPX,
+ 0.43%
they were slightly higher on Tuesday, as investors evaluated progress in the COVID-19 vaccine investigation amid fears of a surge in coronavirus in the US states. USA who have relaxed the restrictions.

How COVID-19 is transmitted