[EvaH (OP)]

Dermot says:

As a humanitarian aid worker, I notice that travel has changed significantly as we all need to have a PCR negative test before being able to fly pretty much anywhere. My organisation imposes a 14-day quarantine after arriving in the country even though the government does not. Is this really necessary as everyone on the plane has tested negative? If the risk is to be mitigated perhaps we could do a PCR negative test a day after arrival, but my colleagues seem to think that we need to wait the full 14 days. What do you think?

Any thoughts?

[evan_au]

There are various windows where you may still be infected:
- Due to the time to process the test, you need to have the test perhaps 2-3 days before the flight, or the results may not arrive in time.
- The PCR test is negative for a couple of days after initial infection, as you aren't shedding enough virus.
- You may be infected on the plane, or in the airport terminal on arrival
- So that is up to 6 days where you may become infected, and not show up in the PCR test

It is thought that the incubation period is < 14 days (for 99.9% of patients), so if you are going to come down with COVID-19, it should show its ugly head within that period. And if you are asymptomatic, the infection should be cleared by then.

If the organization does not want to have an internal outbreak (or spread virus among the people it is trying to help), then an abundance of caution is warranted.
- An outbreak of cholera in a Caribbean disaster area was traced to an international organisation that was there to help them...

[alancalverd]

PCR is a gold standard laboratory test, but the "field" results are strongly dependent on operator skill. The safest assumption  is that the passengers on your plane are representative of the population they are drawn from. UK-wide, that's 1 known infection in 60; US-wide, 1 in 30. You can probably double the incidence for health workers.

So if there are say 30 people on your company plane, regardless of their pre-flight test status there is at least a 50% probability that one will be infectious. This is not a good risk for the receiving nation which presumably has even fewer facilities for isolated treatment than your home country.