How Long Does the SARS-CoV-2 Live on Surfaces

How Long Does the SARS-CoV-2 Live on Surfaces

How stable is the presence of SARS-CoV-2 in the environment compared to SARS (Severe Acute Respiratory Syndrome) Virus? On March 10, local time, medRxiv, a medical preprint platform, published a study report on the survival stability of SARS-CoV-2 in aerosols versus on different object surfaces entitled "Aerosol and surface stability of HCoV-19 (SARS-CoV-2) compared to SARS-CoV-1".   The team found that the SARS-CoV-2 survived up to 3 hours in air aerosols with a half-life of 2.7 hours; 24 hours on paper materials, 4 hours on copper surfaces, and 2–3 days on plastic and stainless steel surfaces.   The researchers say the SARS-CoV-2 and SARS coronavirus are present in the environment for similar periods of time, and that the time for the SARS-CoV-2 to be active on aerosols and object surfaces may be associated with nosocomial infections and supertransmission events, and suggest that it is important to clean and disinfect various solid surfaces.   "Aerosol" refers to the particles suspended in the gas, such as small droplets in the air. In the "Pneumonia Diagnosis and Treatment Plan for SARS-CoV-2 Infection (Fifth Edition for Trial)" previously issued by the National Health Commission of China, the description of the virus transmission route was newly supplemented with "the transmission routes such as aerosol and digestive tract remain to be clarified". However, a number of experts also said that the current transmission route of the SARS-CoV-2 is still based on close respiratory droplet transmission and contact transmission.   The authors of the article are from the National Institute of Allergy and Infectious Diseases (NIAID), the National Institutes of Health, Princeton University, and the University of California, Los Angeles, and the corresponding authors are Neeltje van Doremalen and Trenton Bushmaker, heads of research at the NIAID Virology Laboratory, and Dylan H. Morris, from the Department of Ecological and Evolutionary Biology, Princeton University. The article has not been peer-reviewed.   The authors stated that airborne and vector-borne transmission (fomite transmission, i.e., virus transmission through object vectors) played an important role in previous SARS and MERS epidemics, so quantifying the stability of new coronary viruses in the environment was essential to analyze their virological characteristics.     In this study, the authors used the nCoV-WA1-2020 (MN985325.1) and the SARS coronavirus Tor2 (AY274119.3) for comparison.   The study used a liquid stomatal aerosol generator and a container called "Goldberg drum" to obtain live SARS-CoV-2, that is, to measure the activity of viral particles by atomizing them first by simulating coughing and sneezing in infected individuals and then allowing them to stay in the environment for a period of time. The authors also estimated the decay rate of viable viruses using a Bayesian regression model. The researchers collected samples at 0, 30, 60, 120, and 180 minutes after aerosolization of viral particles and performed a total of three replicates.   They found that live virus could survive for 3 hours in aerosols after nebulization, and the range of viral activity was similar to that of SARS coronavirus.   Through the distribution of virus decay rate, the researchers also calculated the half-life distribution of the SARS-CoV-2 and SARS virus (the time required for half of the virus to decay) under various conditions.   Both SARS-CoV-2 and SARS coronavirus showed similar half-lives in aerosols, with estimates of about 2.7 hours, and 95% confidence intervals of the half-life of SARS-CoV-2 were 1.65–7.24 hours; those of SARS virus were 1.81–5.45 hours.   The researchers also performed experiments on the surface of materials capable of representing a variety of home and hospital environments, including plastic (polypropylene), alloy stainless steel, copper, and cardboard.   The researchers deposited 50 μl of the virus on the surface of different materials and assessed the stability of the virus on this surface by wiping the surface recovery sample, which in turn was end-point titrated on Vero E6 cells to quantify viable virus in all samples. The authors note that the experimental limitation is that copper in undiluted samples may be toxic.   The researchers found that the SARS-CoV-2 was the most stable on plastic and stainless steel and survived for up to 72 hours, although the concentration of the three viruses had been greatly reduced. SARS coronavirus has similar stability, surviving up to 72 hours on polypropylene and 48 hours on stainless steel.   It is worth noting that from the half-life point of view, on the surface of this material, the half-life of the SARS-CoV-2 is significantly higher than that of the SARS virus, with a median value of 8.45 hours.   In addition, both coronaviruses showed significant survival on stainless steel and polypropylene than on other material surfaces: the median half-life of the SARS-CoV-2 was about 13 hours on steel and 16 hours on polypropylene.   The researchers say there is a remarkable feature of previous SARS outbreaks: the occurrence of superspreading events, in which a single case infects a large number of secondary cases, and outbreaks with a large basic number of infections (R0) can overwhelm hospitals and public health.   There have also been some reports on the hypothesis of "superspreading events" in the spread of SARS-CoV-2. Since the superspreading event of SARS virus is related to its aerosol transmission and vector-borne transmission, the researchers said, "We found that the viability of the new coronary virus in the environment is comparable to that of the SARS coronavirus, which also provides evidence for the hypothesis that there may be superspreading of the new coronary virus."   According to previous studies, the main transmission route of the SARS virus is a nosocomial transmission, and SARS coronavirus has been detected on various surfaces and objects in medical institutions.   Transmission of SARS-CoV-2 also occurs in many hospitals, with more than 3000 cases of nosocomial infections reported. These cases highlight the vulnerability of the medical environment to the prevention of entry and transmission of SARS-CoV-2.   In addition, in contrast to the SARS virus, most secondary transmission of superspreading also occurs in many places outside medical institutions, such as universal transmission in communities, families, workplaces, and group gatherings.   At the end of the article, the authors write, overall, the results suggest that it is "plausible" that the virus can survive for hours in aerosols and days on object surfaces through aerosol and material-borne transmission.   But at the same time, the authors also stated that compared with the SARS virus, the SARS-CoV-2 does not have stronger environmental viability. Therefore, the stronger transmission ability of the SARS-CoV-2 observed so far is unlikely to be due to its environmental viability.   There are a number of potential factors that may explain the ability of the virus to spread, for example, early indications that individuals infected with the virus may transmit the virus before they are symptomatic. Therefore, compared with the SARS virus, the characteristics reduce the efficacy of control measures such as isolation and contact tracing.   Other factors that may contribute to the ability of the virus to spread include the amount of virus needed to infect, the stability of the virus in the patient's mucus, and environmental factors such as temperature and relative humidity.   Researchers are conducting new experiments to study the viability of the virus in different matrices (e.g., nasal secretions, sputum, and feces) and under changing environmental conditions (e.g., temperature and relative humidity).   Julie Fischer, a professor of microbiology at Georgetown University, commented on the study. "What we need to do is wash our hands and not touch our faces, because the virus can contaminate the surface of objects."
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