The coronavirus pandemic first emerged in China in late December 2019. From there, it has spread to 188 countries and territories. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of the COVID-19 pandemic, has infected more than 11.4 million people, killing at least 533,000 as of June 6, 2020. The World Health Organization (WHO) has said the coronavirus disease (COVID-19) spreads primarily from person to person via small droplets from the nose or mouth that are expelled when an infected person sneezes, coughs or speaks. The rapid spread of the virus sparked many studies that looked at the length of time these virus-laden aerosols could stay in the air.
Now, a team of international scientists, including 239 health experts from 32 countries, has written an open letter to the WHO urging the organization to revise its recommendations for the spread of SARS-CoV-2, due to mounting evidence that the disease is airborne for more extended periods than the WHO advisory. The researchers intend to publish their letter in the journal Clinical Infectious Diseases shortly. The letter was reported by the Los Angeles Times and the New York Times.
Novel Coronavirus SARS-CoV-2 Transmission electron micrograph of SARS-CoV-2 virus particles, isolated from a patient. Image captured and color-enhanced at the NIAID Integrated Research Facility (IRF) in Fort Detrick, Maryland. Credit: NIAID
The scientists said that multiple studies demonstrate that aerosols can stay in the air for long periods, traveling long distances. The new information makes poorly ventilated rooms, transport vehicles such as trains, buses, and airplanes, and other confirmed spaces dangerous.
Small particles containing the novel coronavirus can infect people upon being inhaled, and they can travel quickly following a sneeze.
In the open letter, the scientists outlined the evidence to the WHO.
“We are 100 percent sure about this,” Lidia Morawska, a Professor in the School of Earth and Atmospheric Sciences, Faculty of Science & Engineering, Queensland University of Technology (QUT) in Brisbane, Australia, told the Los Angeles Times.
“Studies by the signatories and other scientists have demonstrated beyond any reasonable doubt that viruses are exhaled in microdroplets small enough to remain aloft in the air and pose a risk of exposure beyond 1 to 2m by an infected person,” Professor Morawska said.
“At typical indoor air velocities, a 5-micron droplet will travel tens of meters, much greater than the scale of a typical room while settling from a height of 1.5m above the floor. Expertise in many sciences and engineering areas enables us to understand the characteristics and mechanisms behind the generation of respiratory microdroplets, how viruses survive in these microdroplets, and how airflow patterns carry microdroplets in buildings.”
The measures that need to be taken to mitigate airborne transmission include:
- Provide sufficient and adequate ventilation (supply clean outdoor air, minimize recirculating air), particularly in public buildings, workplace environments, schools, hospitals, and aged care homes.
- Supplement general ventilation with airborne infection controls such as local exhaust, high-efficiency air filtration, and germicidal ultraviolet lights.
- Avoid overcrowding, particularly in public transport and public buildings.
“These are practical and can be easily implemented, and many are not costly. For example, simple steps such as opening both doors and windows can dramatically increase airflow rates in many buildings”, Morawska said.
As various countries reopening the economy and businesses, the novel coronavirus if finding new victims worldwide, mostly tied to bars, restaurants, casinos, and offices, to name a few. These new clusters of infections may confirm what many scientists have been claiming for months – the virus can linger in the air indoors, even if people stay six feet apart.
The risk of airborne transmission is a significant factor in the pandemic, especially in revising recommendations that have been established months ago. Now, if the virus can hang in the air for long periods, it is essential to wear masks even if indoors. Further, healthcare workers may need to wear N95 masks that filter out even the smallest respiratory droplets, especially since they take care of infected patients.
Professor Morawska said several retrospective studies of the SARS epidemic had shown that airborne transmission was the most likely mechanism that explained the spatial pattern of infections.
“For example, a recent study analyzed the data and video records in a restaurant where three separate groups of diners contracted COVID-19, observed no evidence of direct or indirect contact between the three groups, but modeled how the transmission occurred through the air
“We are concerned that people may think they are fully protected by following the current recommendations, but in fact, additional airborne precautions are needed to reduce the spread of the virus further.”
Latest WHO update
In April, scientists and health experts on air quality and aerosols urged the WHO to recognize the evidence that airborne transmission of the novel coronavirus is a possibility. The WHO responded and arranged a meeting. The agency emphasized that airborne transmission only happens in certain hospital settings.
In the latest update of the health agency on the coronavirus, which was released on June 29, it said that airborne transmission of the virus is only possible after certain medical procedures that produce droplets or aerosols that are smaller than 5 microns, such as intubation.
The WHO added that proper ventilation and N95 mask use are only recommended in those circumstances. It added that infection control guidance had promoted handwashing as the primary prevention strategy amid the coronavirus pandemic.
“Especially in the last couple of months, we have been stating several times that we consider airborne transmission as possible but certainly not supported by solid or even clear evidence. There is a strong debate on this,” Dr. Benedetta Allegranzi, the WHO’s technical lead on infection control, said.
Further, Professor Paul Hunter, a professor in medicine at the University of East Anglia and a member of the WHO infection prevention committee, said that droplet transmission is the primary route of the novel coronavirus spread.
“Aerosol transmission can occur, but it probably isn’t that important in the grand scheme of things. It’s all about droplets. Controlling airborne transmission isn’t going to do that much to control the spread of Covid-19. It’s going to impose unnecessary burdens, particularly in countries where they don’t have enough trained staff or resources already,” he explained.
What can be done
Health experts recommend that if the airborne transmission is indeed a SARS-CoV-2 mode of transmission, it is vital to wear masks even if indoors, even in settings where social distancing is enforced.
Proper ventilation is also essential, and tighter regulations are needed for ventilation and air condition to reduce recirculating air. Ultraviolet lights in buildings can also help ward off the viruses that linger in the air.
The WHO has not yet responded to the letter.