Coronaviruses are common, and typically cause mild respiratory conditions, such as a cough or runny nose.
But some are more serious – such as the deadly Sars (Severe Acute Respiratory Syndrome) and Middle East Respiratory Syndrome (Mers).
This outbreak – known as novel coronavirus (nCoV) – is a new strain that has not been previously identified in humans.
It seems to start with a fever, followed by a dry cough and then, after a week, leads to shortness of breath.
But in more severe cases, infection can cause pneumonia, severe acute respiratory syndrome, kidney failure and even death.
Most victims have been elderly people, suffering from other chronic diseases including Parkinson’s and diabetes.