Environmental persistence refers to the length of time a pathogen, like SARS-CoV-2, is capable of surviving outside of the human body; the longer it survives, the more likely it is to cause an infection. The persistence of viruses can be affected by both the type of environment (e.g. surface, water, wastewater) as well as the physical and chemical properties of the environment (e.g. temperature, pH, humidity, sunlight exposure). Enveloped viruses, like SARS-CoV-2, are less likely to persist in the environment than non-enveloped viruses, such as norovirus and rotavirus.
Faeces: SARS-CoV-1, a related coronavirus and the virus that causes Severe Acute Respiratory Syndrome (SARS), can survive for hours to days in faeces depending on the source (baby versus adult) and characteristics (diarrhoeal vs non-diarrhoeal) of the faeces (Study 1, Study 2).
Surfaces: SARS-CoV-2 can survive for 2 hours to 9 days under laboratory conditions on different surfaces but is susceptible to surface disinfection. Please refer to the Surfaces section for more information.
Water: SARS-CoV-2 genetic material, but not infectious virus, has been detected in surface water directly impacted by untreated or inadequately wastewater or subject to combined sewer overflows (Study 1, Study 2). Currently, no data are available on the survival of SARS-CoV-2 in water although related viruses can survive in untreated water for days to weeks (Study 1, Study 2, Study 3), with longer survival times observed in colder waters. Conventional filtration and disinfection processes at water treatment facilities should effectively remove or inactivate SARS-CoV-2. The WHO states that there is no indication that SARS-CoV-2 can persist in treated drinking water.
Wastewater: SARS-CoV-2 genetic material has been detected in untreated wastewater (Study 1, Study 2, Study 3, Study 4) but there are no reports of the detection or persistence of viable, infectious SARS-CoV-2 in wastewater. Similar viruses can remain infectious for days to weeks in untreated wastewater (Study 1, Study 2, Study 3). Conventional wastewater treatment processes should reduce risk posed by SARS-CoV-2 in wastewater.
Temperature: SARS-CoV-2 is sensitive to heat and will be quickly inactivated (killed) at high temperatures. For example, at temperatures of 70°C or higher, the virus will survive for five minutes or less. At 4°C, the virus is stable and is able to persist for weeks with little reduction in concentration.
pH: Many pathogens are sensitive to large fluctuations in pH (a measure of how acidic or basic an environment or substance is). One study has found that SARS-CoV-2 can survive in a wide range of pH values (pH 3-10).
Humidity: The coronaviruses that cause SARS and Middle East Respiratory Syndrome (MERS), as well as other coronaviruses, seem to survive longer at lower relative humidity though the effect of humidity on virus survival may also depend on temperature.
Sunlight exposure: SARS-CoV-2 may be less persistent in environments exposed to sunlight due to increased temperature (see above) as well as exposure to solar ultraviolet (UV) radiation. Similar to other coronaviruses, SARS-CoV-2 is predicted to be sensitive to UV rays and is estimated to survive for only minutes during midday summer sun and up to a day during the winter in most regions. No data are currently available on the effectiveness of solar irradiation on inactivating SARS-CoV-2 specifically.