A fomite is an object or surface that can become contaminated with infectious pathogens and serve as a vehicle for their transmission. At the onset of the COVID-19 pandemic, this concept generated widespread concern. Public health messaging emphasized contracting SARS-CoV-2 by touching a contaminated surface, leading to a global surge in intensive cleaning protocols and disinfectant sales. This initial response was driven by an abundance of caution in the face of a novel virus.
Virus Viability on Surfaces
Initial laboratory research fueled concerns over fomite transmission by demonstrating the virus’s ability to persist on various materials. An influential early study found SARS-CoV-2 could be detected for up to 72 hours on plastic and 48 hours on stainless steel under controlled lab conditions. On porous surfaces like cardboard, the virus was not detectable after 24 hours, while on copper, it was gone in four hours. These findings, generated in ideal lab environments, shaped public perception.
A distinction exists between detecting viral RNA and a live, infectious virus. Viral RNA is the genetic material of the virus, which can be detected long after the virus is damaged and no longer capable of infecting a human cell. Many early studies detected this genetic material, not a viable virus, meaning the presence of RNA does not necessarily indicate a risk of transmission.
The survival of the virus on any surface is also influenced by environmental factors. Factors such as temperature, humidity, and exposure to ultraviolet (UV) light from the sun can significantly shorten the lifespan of SARS-CoV-2. The virus degrades much faster at higher temperatures and humidity levels. This is important, as lab settings do not accurately reflect the variable conditions of real-world surfaces.
The Reality of Fomite Transmission Risk
Despite the virus’s capacity to survive on surfaces in a lab, the real-world risk of transmission through fomites is now understood to be low. The U.S. Centers for Disease Control and Prevention (CDC) states that the chances of infection from touching a contaminated surface are less than 1 in 10,000. This conclusion is based on risk assessments that consider the full sequence of events required for infection.
For fomite transmission to be successful, a specific chain of events must unfold. First, an infected person must deposit a sufficient amount of infectious virus on a surface. The virus must then survive long enough for another person to touch that spot. That person must then transfer an adequate amount of the virus to their mouth, nose, or eyes before it is washed off or becomes non-viable. The inefficiency of this multi-step process is a primary reason why fomite transmission is rare.
This low probability contrasts with the primary mode of transmission for SARS-CoV-2: the inhalation of respiratory droplets and aerosols. When an infected person breathes, talks, or coughs, they release virus-containing particles that can be directly inhaled by others nearby. This method is a more direct and efficient route for the virus to enter the respiratory system compared to the journey via a fomite.
Effective Disinfection and Prevention
Simple, targeted measures are the most effective ways to prevent fomite transmission. The primary action an individual can take is consistent hand hygiene. Washing hands with soap and water for at least 20 seconds or using an alcohol-based hand sanitizer with at least 60% alcohol effectively removes or inactivates the virus.
Rather than engaging in exhaustive disinfection, a more measured approach is recommended. Routine cleaning of high-touch surfaces with standard household detergents or soaps is sufficient to further reduce the already low risk. These surfaces include items frequently handled by multiple people, such as doorknobs, light switches, faucets, and countertops.
The intensive, large-scale disinfection efforts seen earlier in the pandemic are now often called “hygiene theater.” This term describes visible cleaning practices that create a sense of security but do little to reduce the actual risk of an airborne virus. While well-intentioned, practices like fogging entire rooms or constant deep cleaning are not an efficient use of resources for preventing COVID-19. The focus has since shifted to personal hygiene and improving indoor air ventilation.