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The novel coronavirus outbreak, coronavirus disease 2019, which was declared pandemic by the World Health Organization on March 11 2020, has infected over 4 million people and caused nearly 300 000 fatalities in over 188 countries. Intensive effort is ongoing worldwide to establish effective treatments and develop vaccines for disease. Novel coronavirus, named as severe acute Respiratory Syndrome coronavirus 2, belongs to the family of pathogen that is responsible for respiratory illnesses linked to the 2002-2003 outbreak. The Envelop virus contains a positive-sense single-strand RNA genome and a nucleocapsid of helical symmetry of 120 nm. There exist several plausible pathways for viruses to be transmitted from person to person. Human atomization of virus-bearing particles occurs from coughing / sneezing and even from normal breathing / talking by an infected person. These mechanisms of viral shedding produce large droplets and small aerosols, which are conventionally delineate at size of 5 m to characterize their distinct dispersion efficiencies and residence times in air as well as deposition patterns along the human respiratory tract. Virus transmission occurs via direct or indirect contact and airborne routes. Large droplets readily settle out of the air to cause person / object contamination; in contrast, aerosols are efficiently disperse in the air. While transmission via direct or indirect contact occurs in short range, airborne transmission via aerosols can occur over extended distances and time. Inhale virus-bearing aerosols deposit directly along the human respiratory tract. Previous experimental and observational studies on interhuman transmission have indicated significant role of aerosols in transmission of many respiratory viruses, including influenza virus, SARS-CoV-1, and Middle East Respiratory Syndrome coronavirus. For example, airborne coronavirus MERS-CoV exhibits strong capability of surviving, with about 64 % of microorganisms remaining infectious 60 min after atomization at 25 C and 79 % relative humidity. On the other hand, rapid virus decay occur, with only 5 % survival over 60-min procedure at 38 C and 24 % RH, indicative of inactivation. Recent experimental studies have examined the stability of SARS-CoV-2, showing that the virus remains infectious in aerosols for hours and on surfaces up to days. Several parameters likely influence microorganism survival and delivery in the air, including temperature, humidity, microbial resistance to external physical and biological stresses, and solar ultraviolet radiation. Transmission and infectivity of airborne viruses are also dependent on the size and number concentration of inhaled aerosols, which regulate amount and pattern for respiratory deposition. With typical nasal breathing, inhalation of airborne viruses leads to direct and continuous deposition into the human respiratory tract. In particular, fine aerosols penetrate deeply into the respiratory tract and even reach other vital organs. In addition, viral shedding is dependent on stages of infection and varies between symptomatic and asymptomatic carriers. Recent findings show that the highest viral load in the upper respiratory tract occurs at symptom onset, suggesting peak of infectiousness on or before symptom onset and substantial asymptomatic transmission for SARS-CoV-2.
A study by a team of researchers lead by Texas & M University Professor has found that not wearing a face mask dramatically increases person's chances of being infected by the COVID-19 virus. Renyi Zhang, Texas & M distinguish Professor of Atmospheric Sciences and Harold J. Haynes Chair in College of Geosciences, and colleagues from the University of Texas, University of California-San Diego and California Institute of Technology have had their work published in the current issue of PNAS. The team examined chances of COVID-19 infection and how the virus is easily passed from person to person. From trends and mitigation procedures in China, Italy and New York City, researchers find that using face masks reduced the number of infections by more than 78 000 in Italy from April 6-May 9 and by over 66 000 in New York City from April 17-May 9. Our results clearly show that airborne transmission via respiratory aerosols represents the dominant route for spread of COVID-19, Zhang say. By analyzing pandemic trends without face-covering using statistical method and by projecting trend, we calculate that over 66 000 infections were prevented by using face masks in little over a month in New York City. We conclude that wearing face masks in public corresponds as the most effective means to prevent inter-human transmission. This inexpensive practice, in conjunction with social distancing and other procedures, is the most likely opportunity to stop the COVID-19 pandemic. Our work also highlights that sound science is essential in decision-making for current and future public health pandemics. One of the paper's co-authors, Mario Molina, is Professor at University of California-San Diego and co-recipient of the 1995 Nobel Prize in Chemistry for his role in understanding the threat to Earth's ozone layer of human-make halocarbon gases. Our study establishes very clearly that using a face mask is not only useful to prevent infected coughing droplets from reaching uninfected persons, but is also crucial for these uninfected people to avoid breathing minute Atmospheric particles that infect people emit when talking and that can remain in the atmosphere tens of minutes and can travel tens of feet, Molina say. Zhang says that many people in China have wearing face masks for years, mainly because of the bad air quality in the country. So people there are sort of used to this, he say. Mandate face-covering helped China in containing the COVID-19 outbreak. Zhang says the results should send a clear message to people worldwide-wearing face mask is essential in fighting viruses. Our work suggests that failure in containing propagation of COVID-19 pandemic worldwide is largely attributed to unrecognized importance of airborne virus transmission, he say. Social-distancing and washing our hands must continue, but that's not sufficient enough protection. Wearing face mask as well as practicing good hand hygiene and social distancing will greatly reduce the chances of anyone contracting the COVID-19 virus. The study was funded by Robert.
'We conclude that wearing face mask in public corresponds as the most effective means to prevent inter-human transmission, ' he say. Moreover, wearing a face mask is inexpensive practice. Mario Molina, Professor at University of California-San Diego and co-recipient of the 1995 Nobel Prize in Chemistry for his role in analyzing the threat to EARTH's ozone layer of man-make halocarbon gases. Study establish quite clearly that Face Masks are only useful to prevent infected coughing droplets from reaching uninfected persons, but are also crucial for these uninfected people to avoid breathing minute ATMOSPHERIC particles that infect people emit when talking and that can remain in the atmosphere for tens of minutes and can travel tens of feet, ' Molina say. Zhang says that many people in China have been wearing masks for years because of poor air conditions caused by pollution. He said that locals have been used to this mandate and that 'face-covering helped China in containing the COVID-19 outbreak. ' The study also concludes that 'the failure in containing propagation of COVID-19 Pandemic worldwide is largely attributed to unrecognized importance of airborne virus transmission, he say.
Tiny specks, called ultrafine particles, are no wider than one thousandth of human hair and are unregulated according to the World Health Organization. Nonetheless, they are thought to contribute to cardiovascular disease and birth defects. Although auto emissions were already recognized for their role in generating particles smaller than 2. 5 microns, call PM2. 5 particles, This is the first study to find auto emissions also indirectly contribute to generation of large amounts of far smaller UFPs, which are less than 0. 05 microns wide. Renyi Zhang, Texas & M distinguish Professor of Atmospheric Sciences and Harold J. Haynes Chair in Geosciences, and colleagues from UT Austin, University of California-San Diego, California Institute of Technology, Johns Hopkins University and several Chinese universities publish their results this week in the latest issue of PNAS. The team studies auto emissions relevant to urban areas, especially Beijing, which has some of the highest pollution from auto exhaust in the world. Annie Zhang, senior Chemistry major at UT Austin and daughter of Renyi Zhang, began work on a project as a high school summer research intern in her father's lab in 2015. A lot of my work involves analysis of data we obtain from Beijing, as well as trying to understand the relevance of our data as it relates to other urban locations around the world, like Houston, she say. Prior to this study, people thought that sulfur dioxide was a major secondary source for UFPs, but not many people believed that aromatic from auto exhaust would also be a major contributing secondary source for UFP. Ultrafine particles can penetrate easily through human lungs and reach many vital organs, Renyi Zhang say. The impacts of ultrafine particles on human health can be far-reaching. Currently, ultrafine particles are unregulated. They can be present in high concentrations, but you still see blue sky. The study was funded by the National Natural Science Foundation of China, Robert. Welch Foundation, and a collaborative research program between Texas & M University and the National Natural Science Foundation of China.
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