The U.S. department of agriculture put out a statement in February 2021 in which they wished to underscore that at the time there is no epidemiologic or scientific information that COVID-19 spreads via food or food packaging.

The press release continues to state "that COVID-19 is a respiratory illness that is spread from person to person". Which stuck with me.

Why are touch surfaces even considered potentially contagious when Covid-19 is a respiratory disease contracted by breathing in virus particles?

  • 2
    $\begingroup$ I do think this sort of question is better posted on SE Medical Sciences than here, as it does not involve any basic biological principle. Anyone answering this sort of question here is unlikely to be a specialist and is more likely to be repeating what they have read recently in the scientific literature. There was an piece on this topic in a recent issue of Nature, which you could try searching for yourself. $\endgroup$
    – David
    Feb 23 at 17:46
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    $\begingroup$ skeptics.stackexchange.com/a/47225/29579 $\endgroup$
    – Fizz
    Feb 23 at 18:50

Transmission through inanimate objects is referred to as "fomite" transmission. It's really hard to know exactly how important fomites are for a particular illness. There is, however, strong evidence that respiratory viruses can spread via this method. Generally, the emphasis is on how contact with hands can lead to infection when someone touches their hand to their mouth, nose, or eyes.

The review by Boone & Gerba, 2007 touches on several issues of fomite transmission. In general, it is easiest to demonstrate evidence of the potential rather than the actual rate of fomite transmission, by looking at viability of viruses on surfaces and how well they transfer to other objects and the hands. However, they also write about epidemiological evidence:

Several epidemiological studies have supported laboratory studies by indicating environmental contamination as a potential vehicle for virus transmission. During an outbreak in a Honolulu nursing home, it was determined that staff hands or fomites (e.g., towels, medical cart items, etc.) spread influenza virus (51). An outbreak of coronavirus (SARS) in a Hong Kong apartment complex may have resulted from fecal-oral transmission combined with environmental contamination (62).

When natural rhinovirus colds were studied, rhinovirus was found on 39% of symptomatic individuals' hands (35). Additionally, volunteers touching contaminated objects and/or the fingers of symptomatic individuals had a higher attack rate of colds if they inoculated their own eyes or nose (35).

They also refer to studies of disinfection/hygiene intervention. The only practical way for these methods to interfere with transmission is by preventing fomite transmission, so if cleaning surfaces and washing hands reduces infections, you can infer that these are contributing routes of infection:

In addition, a review article by Barker et al. cited over 15 research studies that indicated a decrease in viral contamination and viral infection when hand washing was used regularly as an intervention (7). Subsequently, disinfection and hygiene intervention studies, which have cited a reduction in nonspecific illnesses, only support interruption of disease transmission.

I've also attached the reference from that Barker et al paper, which is a simple, informative read.

Barker, J., Stevens, D., & Bloomfield, S. F. (2001). Spread and prevention of some common viral infections in community facilities and domestic homes. Journal of Applied Microbiology, 91(1), 7-21.

Boone, S. A., & Gerba, C. P. (2007). Significance of fomites in the spread of respiratory and enteric viral disease. Applied and environmental microbiology, 73(6), 1687-1696.


In addition to the first answer that was posted, I would point out that, like many other coronaviruses, SARS-COV-2 is also an enteric pathogen, capable of primary infection in various GI tissues. To my knowledge, there's no conclusive evidence that an orally transmitted GI infection can cause severe respiratory symptoms (or even occur in the absence of respiratory infection). But it was something that was worth considering at the start of this pandemic, and is still being investigated as a potential risk for certain medical procedures (like fecal microbiota transplantation).


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