A review of existing research recently showed how airborne transmission is contributing to the rapid COVID-19 spread.
The study, Breathing, speaking, coughing or sneezing: What drives transmission of SARS-CoV-2?, published in the Journal of Internal Medicine, shows that airborne transmission of COVID-19 infection through human speech is the "primary contributor" to the pandemic's fast spread.
The study was conducted by researchers at the Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney, National Institutes of Health, Bethesda.
The fast transmission rate takes place when people who are infected, whether they have developed symptoms or not, speak without a mask or other covering on their mouth and nose, the study showed.
Without the masks, respiratory droplets, or small amounts of liquid discharged from the throat and lungs while speaking or coughing, then spreads to others.
The research shows that if the speaker is not wearing a mask, aerosols or droplets can pass through the air, then into the nose and throat of those close to that person.
Dural Role of Masks
The study authors said that if the aerosols reach the lower respiratory tract, which includes the lungs, they can cause COVID-19.
This puts emphasis on the dual role of masks in both controlling the spread of the virus and alleviating its severity, said the researchers.
In a press release, according to a UPI report, study co-author Adriaan Bax said some spit droplets have been seen flying when people talk. However, there are thousands more too tiny to be visible and seen.
When the water is evaporating from the possible virus-rich droplets produced by speech, the droplets float in the air for several minutes like smoke. This puts other people at risk, explained Bax, a biophysicist and a researcher at the National Institute of Diabetes and Digestive and Kidney Diseases.
COVID-19 Spread Through Airborne Droplets
The World Health Organization and the Centers for Disease Control and Prevention, among others, said early in the pandemic that COVID-19 was spread both through airborne droplets and contaminated surfaces.
As researchers examined the virus and its transmission more closely, they found that respiratory droplets discharged from the mouth and nose pass to others through the air. The process have been observed as the main drivers of COVID-19 spread, the CDC said.
This is the reason health authorities strongly advice the public to wear face coverings and keep social distancing, or a six-feet space from others, to limit the transmission of the virus.
"We are in the midst" of a resurgence of detection and understanding as how aerosols are transmitting airborne infectious disease," observed Davic Edwartds, a Harvard biomedical engineer who has studied the spread of COVID-19..
Speech, cough and the spread droplets, are typically involved in the airborne transmission of the disease although there is no adequate data to assume that one is predominant over the other, added Edwards, who was not part of the new research.
Even Small Amounts of Virus Can Fuel Spread
When an individual infected with COVID-19 speaks or coughs, he or she emits small respiratory particles that are between 95% to 99% liquid, explained Bax.
Once it gets exposed to the air, the liquid in the droplets which contain varying amounts of the virus, evaporates, leaving the virus to scatter and potentially spread to others.
Even droplets with small amounts of the virus can fuel transmission, specifically in confined and crowded indoor places, explained the researchers.
Masks blocking at least 50% of the aerosols, which include many of the cloth face coverings that have become common during the health crisis, can contribute to the limitation of the amount of droplets escaping when an infected individual is speaking and substantially reducing the spread of virus, said the study authors.
Other masks blocking up to 95% of droplets like the N95 and surgical masks are even more effective, researchers said.
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