How is COVID-19 transmitted?
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Understanding COVID-19 Transmission
Human-to-Human Transmission via Respiratory Droplets
COVID-19, caused by the SARS-CoV-2 virus, is primarily transmitted from person to person through respiratory droplets. These droplets are expelled when an infected person coughs, sneezes, or talks, and can be inhaled by individuals in close proximity, leading to infection1 2 8. This mode of transmission is well-documented and is considered the dominant route for the spread of the virus.
Aerosol Transmission in Indoor Environments
Aerosol transmission, where smaller virus-laden particles remain suspended in the air and can be inhaled, is another significant route of COVID-19 spread, especially in indoor settings. Studies have shown that aerosols can effectively transmit the virus in environments such as offices, classrooms, and social gatherings, particularly when ventilation is poor4 5. This mode of transmission underscores the importance of wearing masks and ensuring proper ventilation to reduce infection risk.
Direct Contact and Surface Transmission
Direct contact with infected individuals or contaminated surfaces can also lead to COVID-19 transmission. The virus can survive on surfaces for varying periods, and touching these surfaces followed by touching the face, especially the mouth, nose, or eyes, can result in infection1 8. Regular hand hygiene and disinfection of surfaces are critical preventive measures.
Potential Transmission via Ocular Surfaces
There is some evidence suggesting that the virus may enter the body through the eyes. Although the presence of the virus in conjunctival swabs is not consistently observed, the possibility of transmission through the ocular surface, particularly via the nasolacrimal ducts, cannot be entirely ruled out. Healthcare workers are advised to use eye protection to mitigate this risk3.
Vertical Transmission from Mother to Infant
The likelihood of vertical transmission, where the virus is passed from a pregnant mother to her baby, appears to be low. Studies indicate that only a small percentage of infants born to COVID-19 positive mothers test positive for the virus at birth. However, antibodies against SARS-CoV-2 have been detected in some infants, suggesting some level of natural passive immunity7.
Conclusion
COVID-19 is primarily transmitted through respiratory droplets and aerosols, with direct contact and surface transmission also playing roles. While the potential for ocular and vertical transmission exists, these routes are less common. Preventive measures such as mask-wearing, hand hygiene, surface disinfection, and proper ventilation are essential to curb the spread of the virus. Understanding these transmission mechanisms is crucial for developing effective public health strategies and protecting vulnerable populations.
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Most relevant research papers on this topic
COVID-19 infection: Origin, transmission, and characteristics of human coronaviruses
COVID-19 infection is highly transmistable and pathogenic, with bats as a potential primary reservoir, and no clinically approved antiviral drug or vaccine available.
Literature Review
Highly CitedAtypical modes of COVID-19 transmission: how likely are they?
There is currently no evidence to suggest that COVID-19 can be transmitted via atypical modes of transmission.
Literature Review
Rigorous JournalThe possibility of COVID‐19 transmission from eye to nose
Wearing eye safety goggles when in contact with COVID-19 patients is crucial to prevent transmission from eye to nose.
Rigorous JournalHighly CitedTransmission of Respiratory Viral Diseases to Health Care Workers: COVID-19 as an Example.
Aerosol transmission is likely dominant for COVID-19 among healthcare workers, highlighting the need for updated guidelines and regulations to protect them from infection.
Model Calculations of Aerosol Transmission and Infection Risk of COVID-19 in Indoor Environments
Aerosols from highly infective subjects can effectively transmit COVID-19 in indoor environments, and active room ventilation and face masks can significantly reduce the infection risk by a factor of five to ten.
Rigorous JournalHighly CitedPropagation analysis and prediction of the COVID-19
COVID-19 transmission analysis and prediction models accurately predict epidemic situations within 3% of official data, aiding decision-making for affected countries.
Highly CitedPossible vertical transmission and antibodies against SARS‐CoV‐2 among infants born to mothers with COVID‐19: A living systematic review
A low likelihood of vertical transmission of COVID-19 exists among infants born to mothers with COVID-19, and antibodies against SARS-CoV-2 were detected in 90% of those tested negative for the virus.
Systematic ReviewHighly CitedThe COVID-19 Cytokine Storm; What We Know So Far
Targeting cytokines during COVID-19 patient management could improve survival rates and reduce mortality.
Highly CitedTransmission of COVID-19 to Health Care Personnel During Exposures to a Hospitalized Patient — Solano County, California, February 2020
Early recognition and isolation of COVID-19 patients and use of recommended personal protective equipment can minimize high-risk exposures for healthcare workers.
Case ReportHighly CitedThe origin, transmission and clinical therapies on coronavirus disease 2019 (COVID-19) outbreak – an update on the status
COVID-19 is a novel coronavirus with bats as its natural host, spreads through the respiratory tract, and has caused 2977 deaths worldwide, with few specific antiviral strategies available.
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