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SARS-CoV-2 Transmission: Viral, Host, and Environmental Factors
TAKE-HOME MESSAGE
- The authors conducted a literature review of the data on various modes of SARS-CoV-2 transmission. Live virus has been cultured from aerosols and environmental surfaces hours after inoculation in several experimental studies, but the real-world studies that detected viral RNA in the environment reported very low levels, and few isolated viable viruses. Strong evidence indicates that respiratory transmission is the dominant transmission mode and that proximity and ventilation are key factors. In the few cases where transmission via fomites or direct contact was presumed, respiratory transmission was not definitively excluded.
- Infectiousness appears to peak about 1 day before the individual experiences symptoms and to decline within a week of symptom onset. Although most people do not transmit the virus, "superspreader" transmission clusters may result in many secondary cases.
– Michael Allen, MD
abstract
This abstract is available on the publisher's site.
Access this abstract nowSevere acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the etiologic agent of coronavirus disease 2019 (COVID-19), has spread globally in a few short months. Substantial evidence now supports preliminary conclusions about transmission that can inform rational, evidence-based policies and reduce misinformation on this critical topic. This article presents a comprehensive review of the evidence on transmission of this virus. Although several experimental studies have cultured live virus from aerosols and surfaces hours after inoculation, the real-world studies that detect viral RNA in the environment report very low levels, and few have isolated viable virus. Strong evidence from case and cluster reports indicates that respiratory transmission is dominant, with proximity and ventilation being key determinants of transmission risk. In the few cases where direct contact or fomite transmission is presumed, respiratory transmission has not been completely excluded. Infectiousness peaks around a day before symptom onset and declines within a week of symptom onset, and no late linked transmissions (after a patient has had symptoms for about a week) have been documented. The virus has heterogeneous transmission dynamics: Most persons do not transmit virus, whereas some cause many secondary cases in transmission clusters called “superspreading events.” Evidence-based policies and practices should incorporate the accumulating knowledge about transmission of SARS-CoV-2 to help educate the public and slow the spread of this virus.
Additional Info
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Transmission of SARS-CoV-2: A Review of Viral, Host, and Environmental Factors
Ann. Intern. Med 2020 Sep 17;[EPub Ahead of Print], EA Meyerowitz, A Richterman, RT Gandhi, PE SaxFrom MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
Somedays it feels like an eternity, but is has been just nine months since the first case of SARS-CoV-2 was detected in the U.S. on January 19, 2020.[1] Despite this rather short timeframe, there has been an avalanche of medical literature dealing with COVID-19; my PubMed query on “COVID-19” or “SARS-CoV-2” today returned an impressive 63,481 articles. The challenge for clinicians, public health practitioners, and policymakers is simply keeping up. Well-constructed reviews of recent literature can help.
The recent offering in Annals of Internal Medicine by Meyerowitz and colleagues provides a needed overview of the current thinking on SARS-CoV-2 transmission.[2] Five central topics are approached and summarized below:
My take home from this review: distancing, masking, hand hygiene, surface decontamination, ventilation, isolation of those testing positive for 10 days after symptom onset, and quarantining if exposed continue to be good practices to prevent the spread of SARS-CoV-2.
References