How long does the coronavirus survive in the air, on pavement, steel, cardboard, plastic? Is its viral load sustained or does it diminish?

There are still many questions about how COVID-19 has spread so rapidly in Italy and in other countries. We still have no definite answers. On one thing we can be sure; the fastest and most effective means of transmission is that of contagion among humans. However, researchers are also studying the ability of the virus to survive on surfaces. Let’s consider a few examples.


The massive street-sanitization began in China and then spread to some Italian cities. However, there’s no scientific evidence that the sanitization of pavement is advantageous; on the contrary, since a diluted solution of sodium hypochlorite is used, there is a risk of environmental pollution as various researchers have suggested. At the moment, this practice seems to have been suspended throughout Italy.

In addition, Dr. Pregliasco, a virologist at the State University of Milan, points out that “it’s true that the virus can survive a few days outdoors. The dirt creates a biofilm that acts as a protective barrier to the virus, but it’s quite unlikely that infected droplets are stepped on and then someone touches their shoe’s sole, and then puts their hands in their mouth or fingers in their nose“.


It basically means that the infected droplets remain in the air, suspended. Very recent studies estimate the time-of-stay to be up to three hours.

But under which conditions? Inside an elevator, it’s likely to be a reliable estimate and also an additional reason to climb stairs. Meanwhile outdoors, there are many other factors that come into play; first of all, the wind that can disperse the droplets; even a slight breeze that we barely can perceive easily transports microgram droplets. In addition, UV rays rapidly degrade viruses.

Copper, cardboard, steel and plastic

  • On copper, COVID-19 seems to last at most four hours. Copper is known to degrade microorganisms rapidly.
  • On cardboard, the virus has an estimated survival time of 24 hours.
  • On plastic and steel, the estimated survival time is two-to-three days.

This data comes from several studies performed in the past and repeated (recently), because of the epidemic we’re all experiencing. The most up-to-date study was published by researchers at the National Institute of Allergy and Infectious Diseases of Montana and the University of California Los Angeles (UCLA), together with Princeton University. The article was published in “The New England Journal of Medicine“, an authoritative and highly-respected scientific journal.

The study highlights the risk that may exist, and the role that contaminated surfaces may play in the spread of COVID-19. However, one very important factor must be stressed, in order to prevent the spread of fear of touching any surface. That is, even if the virus is detected on the surfaces listed above, it must be taken into account what the viral load may (still) be.

Other studies done and experiences also with SARS between 2002 and 2003, suggest strongly that the viral load quickly halves, due to exposure to the sun and other atmospheric agents — but more certain data still have to be both collected and communicated.


Should we now go to the grocery store, or do we have our groceries delivered to our homes and ask ourselves the question: do I really have to disinfect everything? How?

To be realistic, we also have to consider it’s quite unlikely that someone has coughed or sneezed on it (i.e. “everything”). However, the rule here also applies as for all other surfaces (that is, that after opening the ham packaging or spaghetti box, I’ll wash my hands thoroughly).

As for vegetables that are not in a bag, you’ll have to wash them well with soap and water, and it would be better to cook them until this emergency is over — and also peel the fruit!

Pollution and very fine dust

A study by the Italian Society of Environmental Medicine (SIMA) was published very recently, linking the effect of air particulate pollution (particulate matter) and the spread of viruses throughout the general population.

Starting from previously known scientific data (i.e. that atmospheric particulate matter can function as a virus transport vector), researchers have related the concentration of particulate matter in certain Italian provinces to the spread of COVID-19. The study suggests that there is a relationship between exceedances of the legal limits of fine dust concentrations recorded in the period between February 10th and 29th — and the number of infected cases was COVID-19 revised-upward on March 3rd.

As is well known, the Po Valley is the area of Italy where the fine dust concentration thresholds are most frequently exceeded, and in fact, it’s also the area where the most cases have been recorded.

The researchers have concluded that very fine dust may have acted as a carrier of the coronavirus and indeed had expanded the area of contagion.

Although it remains to be seen what residual viral load the COVID-19 may have carried via the very fine dust, it seems quite clear that pollution has played a role (and not in our favor), as always — quite the opposite. An additional reason to reflect on the damage we’re doing to the environment, and which is affecting all of us.

Watch this video of NBC New York about coronavirus and surfaces

This post is also available in: Italiano


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