It's actually a very evolving proportion, because, as you can imagine, at the beginning of any outbreak, it is the people who have the most severe symptoms who present. Many of the teams in China are currently unpacking the mild symptoms that are the underside of the iceberg, if you like. The tip of the iceberg is the severe cases. Right now, just proportionately, approximately 20% of cases are considered serious. That means that 80% have some other symptomatology that is less serious. That is the fluctuating proportion based on current data.
On February 5th, 2020. See this statement in context.