All medical experts agree: Social distancing is a critical tool in the fight against the coronavirus, or COVID-19. But how far is far enough away? How long can the virus live in air or on surfaces?
We asked epidemiologist and physician Pedro Kremer, a former family doctor who has experience working with governments and was involved in the management of two outbreaks in Latin America, including the 2009 Severe Acute Respiratory Syndrome, or SARS, outbreak.
First, Dr. Kremer provided a few basic facts about the virus. COVID-19 is a clinical syndrome caused by a novel type of virus within an entire family of viruses. That family is called coronavirus. There are many different kinds, and some cause disease and some do not. SARS was also a type of coronavirus.
COVID-19 is transferred inside little drops sprayed out of the respiratory system as someone coughs, sneezes or talks (usually called ‘respiratory droplets’) which infect people by getting in their eyes, mouth or nose, Kremer explained.
This can happen because the droplets land on or are inhaled by another person standing nearby, usually within 6 feet or so: hence the recommendation of six-feet distance as part of social distancing. (When doctors mention ‘aerosol’ in the context of coronavirus, they mean that the virus is dispersed in air, like say a cough or sneeze, just like other substances are released in air or gas from an aerosol can).
The virus can only live for a matter of seconds –up to a few minutes at most –in air, depending on how moist or hot the air is, Dr. Kremer said. “The information we have so far, most of it says less than three minutes, and some of it mentions as much as ten minutes in certain contexts of heat and humidity,” he said. “It’s not like hours, or days –that’s not true, in any case.”
Kremer is aware of a study cited by the National Institute of Health (NIH) that seemed to show that the virus can survive for hours in air. That study was conducted under very particular conditions, inside a 10-a-half gallon sealed metal drum used to isolate the virus. Kremer said that other studies of the virus in more natural air conditions, such as hospital rooms, showed much shorter survival periods of seconds to minutes.
Because the virus comes out in droplets, it is heavier than most air, and falls onto things, one reason why lengthy airborne survival is unlikely, he added. But people might be also getting the virus by touching things on which the droplets have landed, or surfaces infected by droplets when someone with unwashed hands touched them, Kremer said.
Exactly how long the virus can live on surfaces depends on the type of material. It could vary from minutes to hours, he said. Scientists have made estimates using other strains of coronavirus:
Chart: Survival of Coronaviruses on Surfaces at Room Temperature (68-72°F)
|Type of Coronavirus||Length of Survival|
|Aluminum||Human Coronavirus (HCoV)||2 to 8 hours|
|Latex gloves||(HCoV)||Up to 8 hours|
|Steel||Middle Eastern Respiratory Syndrome (MERS)||48 hours|
|Paper||Severe Acute Respiratory Syndrome (SARS)||24 hours to 5 days|
|Plastic||HCoV||Up to 6 days|
Source: G. Kampf et al. Persistence of Coronaviruses on Inanimate Surfaces, Journal of Hospital Infection 104 (2020): 247/Pedro Kremer
Kremer said that most people do not need to disinfect their entire home. Cleaning takes time, he said, and you’ll want to use that time wisely. “It’s better to be rational,” Kremer said. Clean objects and surfaces that are frequently touched, such as light switches or door handles or with soap and water where possible. Don’t forget that clothing, fabric, hair and skin (and even pets!) can act as surfaces.
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You can use gel and spray sanitizers where soap and water are impossible, like on your phone or remote controls. Read the label before you buy, Kremer said. A bottle that says ‘kills 99.99% of germs’ is not necessarily sufficient to kill the virus. Look for active agents like ethanol (not less than 62 and not more than 95 percent) or sodium hypochlorite bleach (concentrated between .001 to .21 percent; 5 tablespoons per gallon should do it). The Center for Disease Control (CDC) has detailed guidance.
But, Kremer said, the most effective step is still to WASH YOUR HANDS.
The key recommendations to prevent COVID-19 transmission remain the same: stay home if you are sick. Cover your mouth when you cough or sneeze with your elbow or a tissue. Avoid touching your face, especially your eyes, nose and mouth. Sanitize frequently touched objects and surfaces. People without risk factors or pre-existing conditions should call the doctor if you have symptoms of coronavirus BEFORE you go in to an office, unless you are experiencing difficulty breathing or blueness in the face or lips. Finally, and critically: Wash your hands frequently, before and after eating or using the bathroom and after sneezing, coughing or handling objects from outside your home.
Get the latest on COVID-19 from the Centers for Disease Control (CDC) at https://www.cdc.gov/coronavirus/2019-ncov/, and from the DC Department of Health at https://coronavirus.dc.gov/
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