A new study reports that coronavirus remains viable in aerosol for up to 3 hours, a finding that could help inform theories of contagion.
New data on the stability of SARS-CoV-2, which causes COVID-19, show that the virus can remain viable in aerosols for as long as 3 hours and on some surfaces for as long as 3 days. In a series of environmental simulations comparing viability of SARS-CoV-2 with predecessor SARS-CoV-1, NIH researchers found that the 2 viruses behaved similarly in most of the situations.SARS-CoV-1 infected more than 8,000 people globally in 2002 and 2003. According to the most recent update from WHO, there are now 179 111 confirmed cases of COVID-19 infection worldwide. If the durability profiles are similar, what explains why the current outbreak is so much larger?Click through this brief slide show that highlights the study results as well as the authors' thoughts at the end.
Study Methods - aerosols. Aerosols (<5 Î¼m) containing SARS-CoV-2 or SARS-CoV-1 were generated via nebulizer. Samples collected at 0, 30, 60, 120, 180 mins and tested for infectivity on Vero cells. All decay rates for SARS-CoV-2 and SARS-CoV-1 in the study were estimated using Bayesian regression model.
Study methods - surfaces. Virus viability was tested on 4 surfaces for up to 7 days. Ambient environments mimicked a “variety of household and hospital situations.” Viral exposure volumes were consistent with amounts found in upper/lower human respiratory tracts. All surface assays were replicated x3.
Viability in air - 3 hours. SARS-CoV-2 remained viable in aerosols throughout the 3h of the experiment; infectious titer reduction in was slight and was similar to that seen for SARS-CoV-1.
Viability on plastic - 2 to 3 days. SARS-CoV-2 was stable the longest on plastic & stainless steel (vs on copper & cardboard). Viable virus was detected up to 72h after application on both surfaces but viral load was reduced by 3 orders of magnitude (indicative of exponential decay). Similar results seen for SARS-CoV-1.
Viability on stainless steel - 2 to 3 days. Stainless steel and plastic were the most “hospitable” surfaces for both viruses. Median half-life of SARS-CoV-2 was ≈5.6h on stainless steel, and ≈6.8h on plastic. Overall differences in the half-lives were small except for those on cardboard (next slide).
Viability on cardboard - 24 hours. On cardboard, no viable SARS-CoV-2 was measured after 24 hours and no viable SARS-CoV-1 was measured after 8 hours. SARS-CoV-2 showed a considerably longer half-life than SARS-CoV-1 on this surface.
Viability on copper - 4 hours. On copper, no viable SARS-CoV-2 was measured after 4 hours and no viable SARS-CoV-1 was measured after 8 hours. Half-lives on copper were similar between the two viruses.
Authors' conclusions. Aerosol and fomite transmission of the novel virus are both viable-aerosol viability was found to persist for several hours and viability on surfaces to last for days. These similarities are shared with SARS-CoV-1.
Implications for COVID-19 Pandemic. Similarities in stability of SARS-CoV-2 and SARS-CoV-1 under the study conditions suggest that differences in the epidemiology of the 2 viruses are likely related to other factors, including high viral loads in the upper respiratory tract and the potential for shedding and transmission by infected yet asymptomatic persons.
Implications for COVID-19 Pandemic. Transmission of SARS-CoV-1 was associated with nosocomial spread and "superspreading" events (eg, among patients in close proximity in a hospital ED), findings the authors believe will prove valuable to guide current SARS-CoV-2 pandemic containment measures.
Source: N van Doremalen, et al. Aerosol and surface stability of HCoV-19 (SARS-CoV-2) compared to SARS-CoV-1. The New England Journal of Medicine. DOI: 10.1056/NEJMc2004973 (2020).
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