Everyone can do the math. With 100 contacts to contaminated surfaces the chance of infection grows to 0.01. If the chance to become infected per contact are just 1/2000 with 100 contacts the chances of getting infected are now 40%.
It makes perfect sense to maintain surface hygiene since those contacts accumulate statistically.
Mind you, this 1 in 10k risk is an estimate, and for safety reasons, a maximum estimate.
Actual risk is likely much lower, as you have to touch contaminated surface, then transfer the virus to nose, mouth or eyes.
For public areas, properly worn masks help prevent part of the transfer too, by making it mechanically less likely, and giving more time for evaporation to inactivate the virus (e.g. by airflow)
Fomite infection risk would be higher if a contaminated surface is brought to a presumed clean area, with low ventillation, with no additional precautions taken by people.
To think about it another way, if the chance to get infected per touch is 1/10, and you touch a surface 20 times, is your chance of infection 200%? No, that doesn't make sense. It's 1 - ((1 - 1/10) ^ 20) =~ 87.8%.
That's the problem with statistics -- "everyone can do the math", but it's pretty easy to mix it up and reach the wrong conclusions and spread misinformation.
> the chance to become infected per contact are just 1/5000 with 100 contacts
This sounds like gamblers fallacy to me. The number of trials doesn’t change the probability of individual trials in this case because each trial is statistically independent, I saw no mention of e.g. accumulating viral load via successive surface contacts.
From the article, emphasis mine:
> each contact with a contaminated surface has less than a 1 in 10,000 chance of causing an infection
That thought, that "the number of trials doesn’t change the probability of individual trials in this case because each trial is statistically independent" is based on a false assumption that the mathematical statement, observed alone, is all we know about the issue.
And it isn't. We know that the infection happens when enough active viruses appear on the mucosa cells of the host. We know that there are a lot of viruses in every droplet from somebody's nose or mouth. Imagine how much viruses somebody leaves on the surface if he wipes his nose with a hand, for example, and then uses that hand to handle some item.
Finally, we know how much time it takes for half of the viruses to become non functioning (half life) -- something like three days, it is, they remain in the similar numbers for quite a while on the surface. Multiple touches of the same surface on which there is certain number of viruses is nothing like a series of "independent trials."
You missed the if at the start of the sentence. They're not saying that the 100 contacts increases the odds, they're worrying about the effects of 100 contacts if the odds are were underestimated.
If you took all the money spent on sanitising things and instead spent it on buying higher quality masks you'd see a much bigger effect. And this works from the individual, private enterprise or public health perspective.
Everyone can do the math. With 100 contacts to contaminated surfaces the chance of infection grows to 0.01. If the chance to become infected per contact are just 1/2000 with 100 contacts the chances of getting infected are now 40%.
It makes perfect sense to maintain surface hygiene since those contacts accumulate statistically.