In addition, SARS-CoV-2 could not be cultured after incubation with various disinfectants, confirming experimentally the effectiveness of cleaning procedures. The same study found that the virus was highly stable at low temperatures but sensitive to heat, with inactivation of the virus in 5 minutes at 70 ☌. Viral RNA decayed steadily over time in all conditions, although viable virus was isolated for up to 3 hours from aerosols and up to 72 hours from various surfaces the longest reported viability was on plastics and stainless steel, with half-lives around 6 hours ( 1).Ī similar experiment found that infectious virus could be isolated from various surfaces after inoculation with a much larger amount of virus (7 to 8 log units TCID 50/mL) ( 2). Cycle thresholds correlate inversely to viral load, so higher cycle thresholds indicate lower viral loads ( 1). In experimental conditions, viable SARS-CoV-2 was cultured from aerosols (fine particles suspended in the air) and various surfaces after inoculation with 10 5.25 50% tissue culture infectious dose per milliliter (TCID 50/mL) for aerosols and 10 5 TCID 50/mL for surfaces, correlating to a reverse transcriptase polymerase chain reaction cycle threshold of 22 to 24, a typical value obtained from a nasopharyngeal sample of a person with COVID-19. 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. 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. In the few cases where direct contact or fomite transmission is presumed, respiratory transmission has not been completely excluded. Strong evidence from case and cluster reports indicates that respiratory transmission is dominant, with proximity and ventilation being key determinants of transmission risk. 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. This article presents a comprehensive review of the evidence on transmission of this virus. Substantial evidence now supports preliminary conclusions about transmission that can inform rational, evidence-based policies and reduce misinformation on this critical topic. Severe 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. Sax.Ĭollection and assembly of data: E.A. Sax.Ĭritical revision of the article for important intellectual content: E.A.
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Gandhi.Īnalysis and interpretation of the data: E.A. Sax: Division of Infectious Diseases, Department of Medicine, Brigham and Women's Hospital, 15 Francis Street, Boston, MA 02115.Īuthor Contributions: Conception and design: E.A. Gandhi: Division of Infectious Diseases, Department of Medicine, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114.ĭr.
Richterman: Division of Infectious Diseases, Department of Medicine, Hospital of the University of Pennsylvania, 3400 Spruce Street, Philadelphia, PA 19104.ĭr. Meyerowitz: Division of Infectious Diseases, Department of Medicine, Montefiore Medical Center, 111 East 210th Street, Bronx, NY 10467.ĭr. Meyerowitz, MD, Division of Infectious Diseases, Department of Medicine, Montefiore Medical Center, 111 East 210th Street, Bronx, NY 10467 e-mail, Author Addresses: Dr. Disclosures: Disclosures can be viewed at Corresponding Author: Eric A.