Understanding COVID Quarantine Guidance

[russ_watters]

TL;DR Summary

CDC and WHO Guidance on COVID infection response (quarantine) doesn't include use of testing for determining quarantine length. Should it be considered?

Unfortunately this topic is relevant to me now....

CDC Guidance: https://www.cdc.gov/respiratory-viruses/guidance/respiratory-virus-guidance.html
https://www.cdc.gov/respiratory-viruses/guidance/faq.html

You can go back to your normal activities when, for at least 24 hours, both are true:

• Your symptoms are getting better overall, and
• You have not had a fever (and are not using fever-reducing medication).

When you go back to your normal activities, take added precaution over the next 5 days, such as taking additional steps for cleaner air, hygiene, masks, physical distancing, and/or testing when you will be around other people indoors.

• Keep in mind that you may still be able to spread the virus that made you sick, even if you are feeling better. You are likely to be less contagious at this time, depending on factors like how long you were sick or how sick you were.

The CDC has generalized its exposure control guidance to respiratory viruses, not separating/specifying separate criteria for COVID. Note that while it mentions testing, I don't actually see anything in the links (clicking through a few) on how to use it. It just points out that a positive antigen test indicates you are likely contagious.

My interpretation of their logic here is to generalize and simplify the guidance to cover multiple viruses while also conceding that most people aren't going to bother testing (the faq mentions some of this).

WHO Guidance: https://www.who.int/emergencies/diseases/novel-coronavirus-2019/advice-for-public

• If you develop symptoms or test positive for COVID-19, self-isolate until you recover.

[in a separate paragraph]

• Stay home and self-isolate for 10 days from symptom onset, plus three days after symptoms cease.

The WHO guidance is COVID-specific, more stringent (longer isolation) but also more simplistic. My practical concern is that symptoms tend to trail-off very gradually and don't necessarily have a clear-cut date when they "cease". It also doesn't mention use of testing.

Consider the following partly hypothetical case:
Day 0: Mild scratchy throat.
Day 1: Fever, increasing symptoms such as body aches, headache, low energy, runny nose, slight cough, etc. Positive COVID test.
Day 2: Fever breaks, symptoms peak.
Day 3-8: Decreasing symptoms.
Day 4: Positive test.
Day 7: Positive test.
Day 9: Negative test, no symptoms.

If I interpret correctly, CDC guidance would have this person resume normal activities (with masking) starting on Day 4, even with the positive test. WHO would have this person isolate through Day 12. Neither seem to factor-in the positive tests, unless we interpret the first WHO bullet to mean isolation until 3 days after the last positive test. But it also doesn't consider a negative test to be a trigger point.

I'm being fairly conservative and considerate (open/honest about my status), but my question is, specifically: how can one incorporate testing into a COVID isolation protocol, if at all?

[Note: I'll self-report this in case anyone feels it is afoul of our rules on medical advice.]