Masks Are Necessary To Reduce Asymptomatic Transmission Of COVID-19 Through Aerosols And Droplets, Say Health Experts Pandemics & Emergencies 29/05/2020 • Svĕt Lustig Vijay Share this:Click to share on Twitter (Opens in new window)Click to share on LinkedIn (Opens in new window)Click to share on Facebook (Opens in new window)Click to email this to a friend (Opens in new window)Click to print (Opens in new window) Aerosol transmission of COVID-19 is looking to be more significant, and it is ‘essential’ to introduce widespread mask use to reduce COVID-19 transmission by that route – aerosol chemists and infectious disease researchers wrote in a commentary published in Science. The authors refer to a growing body of evidence on aerosols and masks that runs counter to the WHO’s advice – which has not recognized aerosols as a key driver of COVID-19 transmission and has warned against widespread mask use. The WHO has maintained that contact with people or contaminated surfaces is the main route of transmission, rather than aerosols. However, a ‘large proportion’ of COVID-19 spread appears to occur through ‘airborne transmission of aerosols’, especially in asymptomatic individuals when they breathe and speak, suggest researchers from the University of California and National Sun Yat-sen University in China and Taiwan. Two of the authors of the commentary, Kimberly A.Prather and Chia C. Wwang, study aerosolization of chemicals – and the third author, Robert T. Schooley, is affiliated with the infectious disease department at the University of California. In a Wuhan commentary, up to 80% of COVID-19 transmission was asymptomatic, though the US CDC’s estimate is about 35%. The article also mentions that countries which successfully curbed COVID-19 outbreaks and avoided full-blown lockdowns – Taiwan, China, Singapore, Republic of Korea – largely implemented masks, while hard-hit regions that did less well, like New York, did not use masks. Aerosol transmission must be recognized as one of the ‘major’ routes of transmission of the virus, urged the commentary: ‘Aerosol transmission of viruses must be acknowledged as a key factor leading to spread of infectious respiratory diseases…Evidence suggests that SARS-CoV-2 is silently spreading in aerosols exhaled by highly contagious individuals with no symptoms.” When individuals with COVID-19 sneeze or cough, droplets containing the virus are released into the air. These droplets can evaporate into thousands of aerosols that float in the air for almost half a day, potentially infecting other individuals. Airborne transmission has been reported in other respiratory viruses like measles, SARS and chickenpox – And recent evidence demonstrates that 1 minute of loud speaking can generate over a thousand infectious virus-containing aerosols. Given that people with COVID-19 are highly contagious several days before symptoms occur, these ‘silent shedders’ of the virus may be ‘critical drivers’ of COVID-19 transmission, especially in poorly-ventilated areas like health care settings, airplanes or restaurants, reported the commentary. Masks provide a ‘critical barrier’ to reduce COVID-19 transmission in exhaled breath, especially in people that are asymptomatic and those with mild symptoms, stated researchers. Masks should we worn even when people are 6 ft apart, especially in crowded areas, they said. Dr Tedros at a regular press briefing The commentary comes in contradiction to WHO’s guidance from late March. The WHO has largely refrained from widespread mask use, mainly because of the shortage in supplies that are already-limited in critical populations – healthcare workers, older people and other vulnerable populations with underlying conditions. While the WHO has acknowledged that aerosols can form under certain surgical procedures – like intubation for patients that need a ventilator to breathe – the Organization has not recognized it as a key route of transmission, citing ‘respiratory droplets’ and ‘contact’ as the ‘main modes of transmission.’ The WHO’s recommendations ‘are based on studies of respiratory droplets carried out in the 1930s,’ when technologies necessary to detect aerosols ‘did not exist’, said researchers. Homemade masks could be used to protect the general population against COVID-19, while also avoiding mask shortages: “The aerosol filtering efficiency [of]… homemade masks was recently found to be similar to that of the medical masks that were tested. Thus, the option of universal masking is no longer held back by shortages.” The commentary could also shed light into why some individuals have severe COVID-19 while others do not. Given that aerosols are below 1 micron in size – as compared to respiratory droplets which range between 0.1-1000 microns – aerosols could reach deeper parts of the lungs, where immune responses are ‘temporarily bypassed.’ Influenza virus is more severe when it is spread in smaller aerosols compared to respiratory droplets, suggested one commentary. Image Credits: Flickr/Nicolò Lazzati, V.Altounian / Science. Share this:Click to share on Twitter (Opens in new window)Click to share on LinkedIn (Opens in new window)Click to share on Facebook (Opens in new window)Click to email this to a friend (Opens in new window)Click to print (Opens in new window) Combat the infodemic in health information and support health policy reporting from the global South. 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