: Are COVID-19 patients infectious even if test results are negative? With Covid-19, are people infectious in the first days after infection before they test positive on a Covid test? I have learned that Covid-19 tests are

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Are COVID-19 patients infectious even if test results are negative?
With Covid-19, are people infectious in the first days after infection before they test positive on a Covid test?
I have learned that Covid-19 tests are ineffective in the first few days after being infected: in those first few days, you'll likely test negative even though you have the virus. As I understand it, it takes time for the viral load to grow high enough for the test to detect it, so someone who is infected will be likely to test negative in the first few days after being infected. For instance, one study reports a 67% false negative rate 4 days after infection and 20% after 8 days [1].
Could people be infectious during those days before testing positive? I know that people can be infectious before they show any symptoms; does this mean that people might be infectious 4-8 days before they tested positive? Or does it mean that the viral load in the first few days is so low that during the time window when Covid tests are negative, people are unlikely to infect others precisely because their viral load is low? I know the CDC recommends quarantining for 14 days after you might have been exposed, even if you test negative, but I don't know if this recommendation is primarily out of an abundance of caution [2].
I'm wondering about the implications for very frequent testing: e.g., daily Covid-19 testing. Does the delay in testing positive mean that daily Covid-19 testing is insufficient to prevent outbreaks, because people who get infected can still spread the virus for several days before they test positive? Or is it that in the first few days after infection, people are likely to test negative but are also unlikely to infect others?
[1] Variation in False-Negative Rate of Reverse Transcriptase Polymerase Chain Reaction–Based SARS-CoV-2 Tests by Time Since Exposure.
Lauren M. Kucirka, Stephen A. Lauer, Oliver Laeyendecker, Denali Boon, Justin Lessler. Annals of Internal Medicine, 18 August 2020. www.acpjournals.org/doi/10.7326/M20-1495#s1-M201495 [2] www.cdc.gov/coronavirus/2019-ncov/if-you-are-sick/quarantine.html

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