One of severe symptoms of COVID-19 is extremely low blood oxygen level, or hypoxia, which causes blood clotting. In most cases of lung diseases, like pneumonia, low oxygen saturation in blood results to fluid-filled or stiff lungs, increased level of carbon dioxide, and shortness of breath. However, many COVID-19 patients with hypoxia didn't actually show any of these signs in the early stage of infection. Doctors reported that these patients live their lives normally and generally describe themselves as comfortable.
On the onset of COVID-19 pandemic, many of us were forced to stay in our houses. Even so, we still have to go out every now and then to either buy food, medicine, or just simply go to work. This made a lot of us to be fearful that we may have been in contact with someone who has the virus while we're outside and that we may have also contracted the disease.