Coronavirus Disease 2019 (COVID-19) is a contagious illness caused by the SARS-CoV-2 virus. A common concern among the public revolves around the possibility of contracting COVID-19 by touching contaminated surfaces. While it is possible for the virus to spread this way, scientific understanding indicates that this route of transmission is less common compared to other primary modes.
How COVID-19 Spreads Through Surfaces
The transmission of SARS-CoV-2 through contaminated surfaces, known as fomite transmission, occurs when respiratory droplets containing the virus land on objects. If an infected individual coughs, sneezes, talks, or sings, these droplets can contaminate nearby surfaces. A person could then become infected if they touch these contaminated objects and subsequently touch their eyes, nose, or mouth before cleaning their hands.
The virus’s ability to survive on surfaces varies depending on the material and environmental conditions. On porous surfaces like fabrics and paper, viable virus typically becomes undetectable within minutes to hours, as droplets evaporate faster due to capillary action within the pores. Conversely, on non-porous surfaces such as stainless steel, plastic, and glass, the virus can remain viable for hours to several days, with some studies indicating survival for up to 28 days under specific laboratory conditions.
Factors such as temperature, relative humidity, and the presence of organic matter significantly influence how long the virus persists. Lower temperatures generally allow the virus to survive for longer periods, while warmer temperatures accelerate its inactivation. Humidity also plays a role, with some studies suggesting greater survival at very low or very high humidity levels compared to moderate humidity. Despite the virus’s potential to survive on surfaces, public health organizations like the CDC and WHO generally consider the risk of transmission through this route to be low, especially when compared to direct person-to-person spread.
The Primary Modes of COVID-19 Transmission
The SARS-CoV-2 virus primarily spreads between people through respiratory droplets and aerosols when an infected person breathes, coughs, sneezes, talks, or sings. These virus-laden fluid particles are expelled from the mouth and nose. The size of these particles determines their behavior in the air and their potential for transmission.
Respiratory droplets are generally larger particles, typically greater than 5-10 micrometers in diameter, which tend to fall to the ground rapidly within seconds or minutes near the infected person. Transmission through droplets occurs when these particles come into direct contact with another person’s mucous membranes, such as the eyes, nose, or mouth, usually within a close range.
Aerosols, on the other hand, are much smaller particles, typically less than 5-10 micrometers in diameter, which can remain suspended in the air for longer periods and travel over greater distances, particularly in indoor environments. Inhalation of these aerosols can lead to infection, even at distances greater than six feet from an infected individual, especially in poorly ventilated or crowded indoor settings. While both droplets and aerosols contribute to transmission, aerosols are particularly concerning due to their ability to linger and spread throughout a space.
Practical Steps to Reduce Surface Risk
Implementing practical hygiene measures can help reduce the potential risk of COVID-19 transmission from surfaces. Regularly washing hands with soap and water is a foundational practice in preventing the spread of germs, including SARS-CoV-2.
It is recommended to wet hands with running water, apply enough soap to cover all surfaces, and scrub thoroughly for at least 20 seconds, ensuring all parts of the hands, including between fingers and under nails, are cleaned. After scrubbing, hands should be rinsed well under running water and dried completely with a clean towel or air dryer.
When soap and water are not readily available, an alcohol-based hand sanitizer can serve as an effective alternative. For optimal effectiveness against SARS-CoV-2, the sanitizer should contain at least 60% alcohol (ethanol) or 70% isopropanol. Apply a sufficient amount to the palm of one hand and rub it over all surfaces of both hands until they are dry.
Cleaning and disinfecting frequently touched surfaces in homes and workplaces is another important step. High-touch surfaces include door handles, light switches, phones, faucets, and desks. Cleaning with soap and water first removes dirt and germs, while subsequent disinfection kills remaining pathogens. EPA-approved disinfectants effective against COVID-19 should be used according to product instructions, paying attention to contact time for the disinfectant to work. If commercial disinfectants are unavailable, a diluted bleach solution (e.g., 1/3 cup of bleach per gallon of water) can be used, ensuring proper ventilation and safety precautions.