Coronaviruses are a type of virus that can infect humans and cause respiratory disease. The multiple crown-like spikes on the surface of the virus give it the name "corona." Coronaviruses that cause sickness in humans include SARS, Middle East respiratory syndrome (MERS), and the common cold. Hosts' immune systems can aid in the battle against illness. Mammalian hosts have an innate, usually inflammatory, response to infections, which is followed by an adaptive response. The branch of medicine that deals with infections is known as infectious disease. COVID-19 is still a mystery to scientists. What is known is that people who are infected with COVID-19 can disseminate the virus to others before they develop symptoms (when they are still "asymptomatic"). If you do develop symptoms, the CDC states that you are no longer contagious 10 days following the onset of your symptoms.