The quarantine for Covid-19 has been 14 days, not 40.
This magic number, 14, is being fiercely debated in the academic world. One example HERE.
"While the World Health Organization (WHO) estimates the incubation period of COVID-19 could be up to 14 days, this upper limit was actually observed for a small proportion of cases of SARS."
"In the context of an accelerating COVID-19 epidemic and growing uncertainty, a higher upper limit (possibly 21 days) for the incubation period seems reasonable and warranted in the interest of adequately protecting the public."
"One study from China reported an upper limit of 24 days for the COVID-19 incubation period, but the WHO commented that this "can reflect a double exposure" or "outliers," and that the "outlying observation" of 24 days "needs to be taken seriously" but in the "context of all of the other studies."
Note that the 14 day number is based on a small number of patients with different corona virus (SARS vs. Covid-19)
In a different paper, it was claimed that
The first section of the new paper focuses on how long coronaviruses can survive on inanimate surfaces, such as tables and door handles. The authors show that, depending on the material and the conditions, human coronaviruses can remain infectious from 2 hours to 9 days.
At temperatures of around 4°C or 39.2oF, certain versions of the coronavirus could remain viable for up to 28 days.
For giggles, lets consider a high-midrange of the 2 hours-to-9 day range. Pulling a number out of my rectum, let's say seven days for the shady side of the door knob or the bottom of a seat bun. Then add any number you want. Personally, I vote for the 24 days because the speculative dismissal 'could have been double exposure' is a slender reed to justify the risk to billions of potential, down-stream patients.
So, 7+24 give 31 or more than twice the quarantine that is currently being bandied about as bullet-proof. And once you sucked it up and accept 31 days as a defensible duration, why not eliminate all doubt and go the full 40?
28 second recap of Quarantine to-date
I would love to be wrong but the entire response has been a Keystone Cops cartoon.