COVID Virus Loads Peak Well After Symptoms Start

I know several people who have been sick recently, tested negative for COVID-19 when they started getting sick, and eventually recovered with the assumption that it wasn't COVID-19. If this study is correct, that may have been wrong as current variants seem to have a peak in viral load several days after the onset of symptoms.  

Of 348 newly-diagnosed SARS-CoV-2 PCR-positive individuals (65.5% women, median 39.2y), 317/348 (91.1%) had a history of vaccination, natural infection, or both. By both Ct value and antigen concentration measurements, median viral loads rose from the day of symptom onset and peaked on the fourth/fifth day. 

So if you get sick and test negative for COVID-19 at the onset, keep testing and take suitable precautions to protect others until at least the fourth day.