In a new review study, researchers found that COVID-19 is spread most often through respiratory droplets or aerosols and little evidence exists supporting transmission through surfaces.
As such, social distance and proper ventilation are key determinants of transmission risk.
The research was conducted by a team from the Hospital of the University of Pennsylvania and elsewhere.
The team studied scientific articles published between January and September 2020, as well as relevant articles and institutional or governmental reports, to determine the viral, host, and environmental factors that contribute to the transmission of COVID-19.
They found that although several experimental studies suggest that virus particles could live for hours after inoculation in aerosols or on surfaces, the real-world studies that detect viral RNA in the environment report very low levels on surfaces, and few have isolated viable virus.
Strong evidence indicates that respiratory transmission is dominant, with proximity and ventilation being key determinants of transmission risk.
In the few cases where direct contact or transmission from materials or surfaces was presumed, the respiratory transmission could still not be ruled out.
The researchers also found patterns in virus transmission. The evidence showed that the COVID-19 virus peaks around a day before symptom onset and declines within a week of symptom onset.
All transmissions occur early on and none have ever been documented after a patient has had symptoms for about a week.
Most people do not transmit the virus, whereas some cause many secondary cases in transmission clusters called “superspreading events.”
According to the authors, these findings should help to inform evidence-based policies and practices to help educate the public and slow the spread of this virus.
One author of the study is Eric A. Meyerowitz, MD.
The study is published in the Annals of Internal Medicine.
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