How do I count the days to figure out when I should take a COVID test, as it relates to travel? I left the airport around noon on Monday, which was my last contact with the public. I don't have any symptoms or specific known exposure, except that I was traveling.

The recommendation in my area is to take a COVID test 3-5 days after travel and self-quarantine for 7 days after travel or until a negative test. Obviously I can always safely err on the side of a longer quarantine, but how should I count days to get the most accurate test results? How about the fastest reasonably accurate results?

(Lest anyone fret, this was not a pleasure trip. It involved a house that could have been on Hoarders and I'm the next-of-kin.)

  • Maybe take a test only when you have symptoms unless it is mandatory by local authorities – Aak Mar 2 at 14:39
  • @Aak What do you mean "maybe"? Under what circumstances shouldn't I take a test? It is recommended (but not mandatory) to take one in my area after traveling--due to the high number of asymptomatic COVID cases. In particular, I'm under 40, female, and in good health so I'm more likely to have an asymptomatic case if I did contract COVID. I will certainly feel much more comfortable re-integrating into my family after receiving a COVID-negative test result. – user3067860 Mar 2 at 14:46
  • @user3067850 the incubation period could be around 10 days so you may get a positive test on Day 9-10, so self-isolate for 10 days and then take a test to be sure if you want. – Aak Mar 2 at 15:33
  • 1
    @Aak Do you have a citation for 10 days as being the safe number? If so, can you please post an answer. – user3067860 Mar 2 at 16:37
  • Is the asker based in the US? The above looks like US CDC advice but that isn't clear from the question. – Jacob Horbulyk Mar 2 at 19:25

Nothing related to a disease is an exact process where you will always test positive exactly some amount of hours after transmission. In the case where a test is a mandatory requirement, the requirements vary by country, and hopefully the local authorities will have precise instructions in such circumstances, but it's impossible to give a global view of the subject.

In the case where the test is a recommendation rather than a requirement, I'd go with the plain meaning of "after": if you arrive on a Monday, one day after is a Tuesday, so three days after is a Thursday and five days is a Saturday. Getting the test between Thursday and Saturday, then, seems to comply with the suggestion you describe in your post.


You should consult the medical authorities and guidelines issued by the local government but generally, it can take up to 10 days for coronavirus symptoms to appear. Here is an excerpt from guidelines shared by UK government for inbound travelers.

The quarantine period starts the day you arrive in England and ends 10 days after the day you arrived. This period is necessary because it can take up to 10 days for coronavirus symptoms to appear.

Reference - https://www.gov.uk/guidance/how-to-quarantine-when-you-arrive-in-england

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