I have COVID, for how long should I isolate?

If you wear at least an N95 respirator without a valve, there's no reason to isolate.

Frankly, I find it more than a little annoying that the burden of reducing transmission is not more widely shared with the non-infected. In other words, if high-risk people want to avoid getting covid even after they're fully vaxxed and boosted, they should just wear a respirator rather than relying on the kindness of strangers. Isolation might have made more sense when the PPE supply was limited, but that's no longer the case.

One thing you could do is use microCOVID to look at how risky various events are when the other person has covid, and use that as a baseline to make adjustments off of. For example:

• Outdoors, masked, and ~3 feet away from people for an hour is approximately 150 microcovids.
• Indoors and ~6 feet of distance is about 1,500 microcovids.
• Indoors, ~3 feet of distance and unmasked is about 35,000 microcovids.

From there you can make some educated guesses about how much the risk goes down on day N. Microcovid had a blog post a while ago, pre-delta, that has this image:

From what I remember about omicron, the infectiousness window is smaller. Ballparking it, I'll throw out some numbers and guess that on day 5 maybe you are 20% as infectious, and on day 10 you are 1% as infectious. Which would yield updated numbers of 30, 300 and 7,000 microcovids respectively for the above scenarious on day 5, and then 1.5, 15 and 350 microcovids for day 10.

So that gives you a sense of how much risk you'd be exposing others to in various situations, which can inform your conclusion on the broader question of how long and in what ways you should isolate for.

sniffles don't matter; 10 days after fever's end seems generous/considerate. allegedly positive nasal swab antigen tests will persist for days after it's impossible to lab-culture the virus from a snot sample but in any case such tests are definitely negative after 14 days of onset

If you wear a well-fitted n95 (consider sealing the edges to your skin with gentle surgical tape, if you're making do with poorly fitted ones) and keep it on for the entire time, I think any masked activity is acceptable. Then again, wearing a well-fitted n95/KN95/KF94 or better and actually keeping it on is above and beyond what a depressingly high percentage of the population are doing, including most of the healthcare workers I know.

I personally wouldn't consider it appropriate to share air with strangers until after a negative test, but then again, I go out of my way to avoid sharing air with strangers anyways these days and don't find it a major hardship, so I'm probably biased.

I think the major ethical issue of covid these days is making sure not to force anyone to breathe your germs if they don't want to. The argument in favor of doing the CDC-guidelines bare-minimum with respect to restaurants is that, if the restaurant offers a choice between takeaway and indoor seating, everyone who eats indoors is opting into the risk of breathing in what you're breathing out, and not being forced or coerced to be near you in the same way that economic circumstances often force people to shop at grocery stores or ride buses. Those who would rather not breathe strangers' germs, such as myself, get our food to go and eat at home, in a park, or anywhere else we can make ourselves comfortable with good airflow.

This says that 16% of people remain infections at day 7 and 5% of people remain infectious at day 10:

https://ukhsa.blog.gov.uk/2022/01/01/using-lateral-flow-tests-to-reduce-the-self-isolation-period/