Re that “holding your breath for 10 sec” deal, I came across this (no idea if this is legitimate or not):
From member of the Stanford hospital board. This is their feedback for now on Corona virus: The new Coronavirus may not show sign of infection for many days. How can one know if he/she is infected? By the time they have fever and/or cough and go to the hospital, the lung is usually 50% Fibrosis and it's too late. Taiwan experts provide a simple self-check that we can do every morning. Take a deep breath and hold your breath for more than 10 seconds. If you complete it successfully without coughing, without discomfort, stiffness or tightness, etc., it proves there is no Fibrosis in the lungs, basically indicates no infection. In critical time, please self-check every morning in an environment with clean air. Serious excellent advice by Japanese doctors treating COVID-19 cases: Everyone should ensure your mouth & throat are moist, never dry. Take a few sips of water every 15 minutes at least. Why? Even if the virus gets into your mouth, drinking water or other liquids will wash them down through your throat and into the stomach. Once there, your stomach acid will kill all the virus. If you don't drink enough water more regularly, the virus can enter your windpipe and into the lungs. That's very dangerous. Please send and share this with family and friends. Take care everyone and may the world recover from this Coronavirus soon."
To the extent the above is accurate, it sounds like the pneumonia phase happens several days after the fever breaks and in part involves an immune response run amok where antibodies confuse lung tissue with virus and cause fibrosis. This doesn’t happen to everyone but is a main contributing reason people are hospitalized and need ventilation. So it stands to reason a lot of people WILL get and have Covid-19, but not the complicated pneumonia as demonstrated by passing the lung inhalation test. So don’t be misled and be in a position to potentially spread it. At least that’s how I read it. It could be the lung test fails earlier in the onset when fever starts, don’t know.