https://blogs.scientificamerican.com/observations/why-social-media-are-crucial-for-frontline-physicians-in-the-fight-against-covid-19/

The first wave of patients in Brooklyn were what we call the worried well, who arrived at the emergency room with cough, fever and flulike symptoms, concerned they had coronavirus. We would perform a nasal swab, or not, depending on whether we had COVID-19 tests available that day, and send them home with isolation precautions and advice to come back to the ER if they had trouble breathing.

Many of them came back with trouble breathing. The first step for just about everyone short of breath is to provide oxygen through a simple nasal cannula or face mask. For many, that was enough—we performed the usual tests (blood work, chest X-ray) and admitted them to the hospital so that they could continue to receive oxygen until they recovered.