Betacoronavirus , Coronavirus Infections/epidemiology , Pandemics , Pneumonia, Viral/epidemiology , Coronavirus Infections/diagnosis , Coronavirus Infections/history , Coronavirus Infections/transmission , Fear , History, 20th Century , History, 21st Century , History, Ancient , History, Medieval , Humans , Influenza, Human/epidemiology , Influenza, Human/history , Pandemics/history , Plague/epidemiology , Plague/history , Pneumonia, Viral/diagnosis , Pneumonia, Viral/history , Pneumonia, Viral/transmission , Quarantine/history , Social Media , Symptom Assessment , Time Factors