Viruses can spread from human contact with animals. Scientists think MERS started in camels, according to the WHO. With SARS, scientists suspected civet cats were to blame. Officials do not yet know what animal may have caused the current outbreak in Wuhan. When it comes to human-to-human transmission of the viruses, often it happens when someone comes into contact with an infected person's secretions, such as droplets in a cough. Depending on how virulent the virus is, a cough, sneeze or handshake could cause exposure. The virus can also be transmitted by touching something an infected person has touched and then touching your mouth, nose or eyes. Caregivers can sometimes be exposed by handling a patient's waste, according to the CDC. Human-to-human transmission has been confirmed for the Wuhan coronavirus, but experts are now trying to understand who is transmitting it most, who is at most risk and whether transmission is occurring mostly in hospitals or in the community. SARS and MERS were largely transmitted inside hospitals, Horby said. Some people are also considered to be "superspreaders."