Effects of Air Temperature and Relative Humidity on Coronavirus Survival on Surfaces

Abstract

Assessment of the risks posed by severe acute respiratory syndrome (SARS) coronavirus (SARS-CoV) on surfaces requires data on survival of this virus on environmental surfaces and on how survival is affected by environmental variables, such as air temperature (AT) and relative humidity (RH). The use of surrogate viruses has the potential to overcome the challenges of working with SARS-CoV and to increase the available data on coronavirus survival on surfaces. Two potential surrogates were evaluated in this study; transmissible gastroenteritis virus (TGEV) and mouse hepatitis virus (MHV) were used to determine effects of AT and RH on the survival of coronaviruses on stainless steel. At 4°C, infectious virus persisted for as long as 28 days, and the lowest level of inactivation occurred at 20% RH. Inactivation was more rapid at 20°C than at 4°C at all humidity levels; the viruses persisted for 5 to 28 days, and the slowest inactivation occurred at low RH. Both viruses were inactivated more rapidly at 40°C than at 20°C. The relationship between inactivation and RH was not monotonic, and there was greater survival or a greater protective effect at low RH (20%) and high RH (80%) than at moderate RH (50%). There was also evidence of an interaction between AT and RH. The results show that when high numbers of viruses are deposited, TGEV and MHV may survive for days on surfaces at ATs and RHs typical of indoor environments. TGEV and MHV could serve as conservative surrogates for modeling exposure, the risk of transmission, and control measures for pathogenic enveloped viruses, such as SARS-CoV and influenza virus, on health care surfaces.Environmental surfaces have been recognized as likely contributors to the transmission of nosocomial viral infections (25). The question of whether hospital surfaces play a role in the spread of nosocomial viral infection took on particular urgency during the worldwide outbreak of severe acute respiratory syndrome (SARS). SARS was a novel coronavirus infection, and local and institutional outbreaks were driven in part by nosocomial spread; cases of SARS were documented in health care workers, patients, and visitors in health care facilities (20). During outbreaks in health care facilities, surface sampling for SARS coronavirus (SARS-CoV) revealed SARS-CoV nucleic acids on surfaces and inanimate objects (6, 10). This suggests that surfaces could be sources of virus transmission. Assessment of the risk posed by SARS-CoV on surfaces requires data on the survival of the virus on environmental surfaces and data on how this survival is affected by environmental variables, such as air temperature (AT) and relative humidity (RH).Because working with SARS-CoV requires specially trained personnel working under biosafety level 3 (BSL-3) laboratory containment conditions, there are significant challenges in studying this virus, and only limited data on its survival and response to environmental stressors are available. The use of surrogate coronaviruses has the potential to overcome these challenges...

Emerging infectious diseases: Focus on infection control issues for novel coronaviruses (Severe Acute Respiratory Syndrome-CoV and Middle East Respiratory Syndrome-CoV), hemorrhagic fever viruses (Lassa and Ebola), and highly pathogenic avian influenza viruses, A(H5N1) and A(H7N9)

“…This study, studies on SARS-CoV (discussed previously), and studies on other coronaviruses suggest that they survive on environmental surfaces for a sufficient time to allow fomite transmission. 102 Studies on inactivation of SARS-CoV (previously discussed) and other coronaviruses are inactivated within 1 minute by phenolics (1.3-2.0 log10 reduction) and 70% ethanol (3.2-3.9 log10 reduction). 103 Hypochlorite with a 1:00 dilution, had a 1 minute decrease of <1 log10.…”

Transmission of SARS and MERS coronaviruses and influenza virus in healthcare settings: the possible role of dry surface contamination

“…16 Since other human coronaviruses do not share the unusual survival properties of SARS-CoV, TGEV and mouse hepatitis virus (MHV) are often used as surrogates. 26,43,45 No study has tested more than one strain of SARS-CoV or MERS-CoV. However, some studies have tested more than one strain of influenza, highlighting considerable strain variation.…”

“…32,33,39 In all studies that tested varying temperature and RH, lower temperature and RH favoured the survival of both coronaviruses and influenza. 16e18, 26,35,36,38 Different methods have been applied to detect virus e most often cell culture assays but also RNA detection using polymerase chain reaction (PCR) or indirect methods such as fluorescence or haemagglutinin assays. 27,33,34,37,40 Intact viral RNA appears to remain detectable on surfaces for longer than viruses that retain the ability to infect cells.…”

New and emerging infectious diseases (Ebola, Middle Eastern respiratory syndrome coronavirus, carbapenem-resistant Enterobacteriaceae, Candida auris): Focus on environmental survival and germicide susceptibility

“…Multiple studies on CoVs other than MERS-CoV have demonstrated that these viruses can remain viable for days to weeks on environmental surfaces. 88,89 Survival is enhanced at low temperatures (ie, 4°C vs 20°C). 89…”