It is challenging to know at early stages when you are infected by the  novel coronavirus  that causes the COVID-19 disease. There is a most common and rare symptom loss of smell that could signal you must be tested. According to Harvard T.H. Chan School of Public Health epidemiologist  Marc Lipsitch , the virus could ultimately infect between 40% and 70% of the population worldwide. Some people might show no symptoms at all   but many of those cases would be mild, while the prospect of being infected with a new virus can be devastating. The most symptoms, as per the Centre for Disease Control and Prevention (CDC), are fever, coughing and shortness of breath. These symptoms usually appear between two days and two weeks of exposure to the virus. Doctors recently added "loss of smell" as a potential symptom that may show up alone without any other symptoms,  Live Science reported .  As per the  Journal of the American Medical Association , as m...