Can the virus be transmitted through the air?
Can the virus be transmitted through the air?
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According to the World Health Organization (WHO), the virus that causes COVID-19 is primarily spread through respiratory droplets (little spit droplets that fly out when a person sneezes, coughs or talks). Respiratory droplets can infect other people who are nearby, or indirectly infect others when they touch a surface contaminated with infected droplets. After an open letter by scientists in July 2020, the WHO now acknowledges the possibility of airborne transmission, which is caused by smaller and lighter 'droplet nuclei' (residuals of respiratory droplets from infected people) that can remain in the air for longer periods of time and remain infectious over long distances. Experts are looking at previous data from China to see whether the virus may spread through the air or through vents via airborne transmission. While a few lab-based studies have found that the virus can be present in the air for up to three hours, these studies did not assess if the virus is viable to infect anyone else. Recently, a research study published in Nature found viral contamination in air samples from patients isolated at a medical center, which supports the use of airborne isolation precautions in caring for COVID-19 cases. A few studies have also looked into how airborne transmission may have played a role in certain outbreaks, such as the one in the Diamond Princess cruise ship. One of these studies in pre-print found that it was likely that a combination of both close-range (respiratory droplet) transmission and long-range (airborne) transmission contributed similarly to disease progression aboard the ship. Thus far, the WHO still claims that evidence points to close person-to-person respiratory droplet transmission as the primary mode of COVID-19 transmission. However, experts warn that there is significant reason to believe airborne transmission is happening. The U.S. Centers for Disease Control and Prevention (CDC) now provides infection control recommendations for airborne transmission as well as respiratory droplet transmission. Definitive studies may take a long time to alter the body of evidence in the coming weeks and months, but proactive prevention measures such as universal use of masks (the U.S. CDC recommends wearing a cloth mask over a surgical mask for increased protection) could save lives in the meantime.
According to the World Health Organization (WHO), the virus that causes COVID-19 is primarily spread through respiratory droplets (little spit droplets that fly out when a person sneezes, coughs or talks). Respiratory droplets can infect other people who are nearby, or indirectly infect others when they touch a surface contaminated with infected droplets. After an open letter by scientists in July 2020, the WHO now acknowledges the possibility of airborne transmission, which is caused by smaller and lighter 'droplet nuclei' (residuals of respiratory droplets from infected people) that can remain in the air for longer periods of time and remain infectious over long distances. Experts are looking at previous data from China to see whether the virus may spread through the air or through vents via airborne transmission. While a few lab-based studies have found that the virus can be present in the air for up to three hours, these studies did not assess if the virus is viable to infect anyone else. Recently, a research study published in Nature found viral contamination in air samples from patients isolated at a medical center, which supports the use of airborne isolation precautions in caring for COVID-19 cases. A few studies have also looked into how airborne transmission may have played a role in certain outbreaks, such as the one in the Diamond Princess cruise ship. One of these studies in pre-print found that it was likely that a combination of both close-range (respiratory droplet) transmission and long-range (airborne) transmission contributed similarly to disease progression aboard the ship. Thus far, the WHO still claims that evidence points to close person-to-person respiratory droplet transmission as the primary mode of COVID-19 transmission. However, experts warn that there is significant reason to believe airborne transmission is happening. The U.S. Centers for Disease Control and Prevention (CDC) now provides infection control recommendations for airborne transmission as well as respiratory droplet transmission. Definitive studies may take a long time to alter the body of evidence in the coming weeks and months, but proactive prevention measures such as universal use of masks (the U.S. CDC recommends wearing a cloth mask over a surgical mask for increased protection) could save lives in the meantime.
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What our experts say
According to the World Health Organization (WHO), the virus that causes COVID-19 is primarily spread through respiratory droplets (little spit droplets that fly out when a person sneezes, coughs or talks). Respiratory droplets can infect other people who are nearby, or indirectly infect others when they touch a surface contaminated with infected droplets. After an open letter by scientists in July 2020, the WHO now acknowledges the possibility of airborne transmission, which is caused by smaller and lighter 'droplet nuclei' (residuals of respiratory droplets from infected people) that can remain in the air for longer periods of time and remain infectious over long distances.
Experts are looking at previous data from China to see whether the virus may spread through the air or through vents via airborne transmission. While a few lab-based studies have found that the virus can be present in the air for up to three hours, these studies did not assess if the virus is viable to infect anyone else. Recently, a research study published in Nature found viral contamination in air samples from patients isolated at a medical center, which supports the use of airborne isolation precautions in caring for COVID-19 cases. A few studies have also looked into how airborne transmission may have played a role in certain outbreaks, such as the one in the Diamond Princess cruise ship. One of these studies in pre-print found that it was likely that a combination of both close-range (respiratory droplet) transmission and long-range (airborne) transmission contributed similarly to disease progression aboard the ship.
Thus far, the WHO still claims that evidence points to close person-to-person respiratory droplet transmission as the primary mode of COVID-19 transmission. However, experts warn that there is significant reason to believe airborne transmission is happening. The U.S. Centers for Disease Control and Prevention (CDC) now provides infection control recommendations for airborne transmission as well as respiratory droplet transmission. Definitive studies may take a long time to alter the body of evidence in the coming weeks and months, but proactive prevention measures such as universal use of masks (the U.S. CDC recommends wearing a cloth mask over a surgical mask for increased protection) could save lives in the meantime.
According to the World Health Organization (WHO), the virus that causes COVID-19 is primarily spread through respiratory droplets (little spit droplets that fly out when a person sneezes, coughs or talks). Respiratory droplets can infect other people who are nearby, or indirectly infect others when they touch a surface contaminated with infected droplets. After an open letter by scientists in July 2020, the WHO now acknowledges the possibility of airborne transmission, which is caused by smaller and lighter 'droplet nuclei' (residuals of respiratory droplets from infected people) that can remain in the air for longer periods of time and remain infectious over long distances.
Experts are looking at previous data from China to see whether the virus may spread through the air or through vents via airborne transmission. While a few lab-based studies have found that the virus can be present in the air for up to three hours, these studies did not assess if the virus is viable to infect anyone else. Recently, a research study published in Nature found viral contamination in air samples from patients isolated at a medical center, which supports the use of airborne isolation precautions in caring for COVID-19 cases. A few studies have also looked into how airborne transmission may have played a role in certain outbreaks, such as the one in the Diamond Princess cruise ship. One of these studies in pre-print found that it was likely that a combination of both close-range (respiratory droplet) transmission and long-range (airborne) transmission contributed similarly to disease progression aboard the ship.
Thus far, the WHO still claims that evidence points to close person-to-person respiratory droplet transmission as the primary mode of COVID-19 transmission. However, experts warn that there is significant reason to believe airborne transmission is happening. The U.S. Centers for Disease Control and Prevention (CDC) now provides infection control recommendations for airborne transmission as well as respiratory droplet transmission. Definitive studies may take a long time to alter the body of evidence in the coming weeks and months, but proactive prevention measures such as universal use of masks (the U.S. CDC recommends wearing a cloth mask over a surgical mask for increased protection) could save lives in the meantime.
Context and background
Respiratory droplets are little beads of liquids that fly out when a person sneezes, coughs, or uses their mouth. The World Health Organization (WHO) has stated that COVID-19 mainly spreads from person to person through these droplets when people come in close contact with one another. Airborne particles tend to be lighter than respiratory droplets and can stay in the air for longer periods of time, which makes airborne viruses even easier to spread. Some studies have shown that COVID-19 could potentially be spread through the air in enclosed spaces with poor ventilation. The evidence on this mode of transmission is still evolving.
Airborne transmission of COVID-19 is trending in the news, in part because 239 scientists signed an open letter on July 6, 2020 urging the WHO to update its COVID-19 guidance in response to growing evidence that airborne transmission is possible, ranging from case reports to epidemiological studies. The WHO has since acknowledged the emerging evidence for airborne transmission in "crowded, closed, poorly ventilated settings," while cautioning that the evidence is preliminary and should be assessed further. If airborne transmission of COVID-19 is significant, this has major implications for containment efforts (ex. masks may be needed indoors and in socially-distant settings, ventilation systems may need to minimize recirculating air and find ways to filter or disinfect contaminated air, etc.).
Respiratory droplets are little beads of liquids that fly out when a person sneezes, coughs, or uses their mouth. The World Health Organization (WHO) has stated that COVID-19 mainly spreads from person to person through these droplets when people come in close contact with one another. Airborne particles tend to be lighter than respiratory droplets and can stay in the air for longer periods of time, which makes airborne viruses even easier to spread. Some studies have shown that COVID-19 could potentially be spread through the air in enclosed spaces with poor ventilation. The evidence on this mode of transmission is still evolving.
Airborne transmission of COVID-19 is trending in the news, in part because 239 scientists signed an open letter on July 6, 2020 urging the WHO to update its COVID-19 guidance in response to growing evidence that airborne transmission is possible, ranging from case reports to epidemiological studies. The WHO has since acknowledged the emerging evidence for airborne transmission in "crowded, closed, poorly ventilated settings," while cautioning that the evidence is preliminary and should be assessed further. If airborne transmission of COVID-19 is significant, this has major implications for containment efforts (ex. masks may be needed indoors and in socially-distant settings, ventilation systems may need to minimize recirculating air and find ways to filter or disinfect contaminated air, etc.).
Resources
- Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1 (NEJM)
- Turbulent Gas Clouds and Respiratory Pathogen Emissions: Potential Implications for Reducing Transmission of COVID-19 (JAMA)
- Aerodynamic analysis of SARS-CoV-2 in two Wuhan hospitals (unedited but accepted for publication) (Nature)
- High SARS-CoV-2 Attack Rate Following Exposure at a Choir Practice — Skagit County, Washington, March 2020 (U.S. CDC)
- Detection of air and surface contamination by SARS-CoV-2 in hospital rooms of infected patients (Nature)
- Aerosol and surface contamination of SARS-CoV-2 observed in quarantine and isolation care (Nature)
- Mechanistic Transmission Modeling of COVID-19 on the Diamond Princess Cruise Ship Demonstrates the Importance of Aerosol Transmission (medRxiv)
- Airborne Transmission of SARS-CoV-2: Theoretical Considerations and Available Evidence (JAMA)
- Open Letter: It is Time to Address Airborne Transmission of COVID-19 (Clinical Infectious Diseases)
- Coronavirus: WHO rethinking how Covid-19 spreads in air (BBC)
- Modes of transmission of virus causing COVID-19: implications for IPC precaution recommendations (WHO)
- Transmission of SARS-CoV-2: implications for infection prevention precautions (WHO)
- Interim Infection Prevention and Control Recommendations for Healthcare Personnel During the Coronavirus Disease 2019 (COVID-19) Pandemic (U.S. CDC)
- Maximizing Fit for Cloth and Medical Procedure Masks to Improve Performance and Reduce SARS-CoV-2 Transmission and Exposure, 2021 (U.S. CDC)
- Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1 (NEJM)
- Turbulent Gas Clouds and Respiratory Pathogen Emissions: Potential Implications for Reducing Transmission of COVID-19 (JAMA)
- Aerodynamic analysis of SARS-CoV-2 in two Wuhan hospitals (unedited but accepted for publication) (Nature)
- High SARS-CoV-2 Attack Rate Following Exposure at a Choir Practice — Skagit County, Washington, March 2020 (U.S. CDC)
- Detection of air and surface contamination by SARS-CoV-2 in hospital rooms of infected patients (Nature)
- Aerosol and surface contamination of SARS-CoV-2 observed in quarantine and isolation care (Nature)
- Mechanistic Transmission Modeling of COVID-19 on the Diamond Princess Cruise Ship Demonstrates the Importance of Aerosol Transmission (medRxiv)
- Airborne Transmission of SARS-CoV-2: Theoretical Considerations and Available Evidence (JAMA)
- Open Letter: It is Time to Address Airborne Transmission of COVID-19 (Clinical Infectious Diseases)
- Coronavirus: WHO rethinking how Covid-19 spreads in air (BBC)
- Modes of transmission of virus causing COVID-19: implications for IPC precaution recommendations (WHO)
- Transmission of SARS-CoV-2: implications for infection prevention precautions (WHO)
- Interim Infection Prevention and Control Recommendations for Healthcare Personnel During the Coronavirus Disease 2019 (COVID-19) Pandemic (U.S. CDC)
- Maximizing Fit for Cloth and Medical Procedure Masks to Improve Performance and Reduce SARS-CoV-2 Transmission and Exposure, 2021 (U.S. CDC)
