How deadly is new coronavirus? It's still too early to tell

Scientists can't tell yet how deadly the new virus that's spreading around the globe really is and deepening the mystery, the fatality rate differs even within China.

As infections of the virus that causes COVID-19 surge in other countries, even a low fatality rate can add up to lots of victims, and understanding why one place fares better than another becomes critical to unravel.

"You could have bad outcomes with this initially until you really get the hang of how to manage" it, Dr Bruce Aylward, the World Health Organisation envoy who led a team of scientists just back from China, warned on Tuesday.

In the central China city of Wuhan, where the new coronavirus first exploded, 2 per cent to 4 per cent of patients have died, according to WHO. But in the rest of hard-hit China, the death rate was strikingly lower, 0.7 per cent.

There's nothing different about the virus from one place to another. Instead, the never-before-seen strain of coronavirus struck Wuhan fast before anyone knew what the illness was and overwhelmed health facilities. As is usual at the beginning of an outbreak, the first patients were severely ill before they sought care, Aylward said.

By the time people were getting sick in other parts of China, authorities were better able to spot milder cases meaning there were more known infections for each death counted.

And while there are no specific treatments for COVID-19, earlier supportive care may help, too. China went from about 15 days between onset of symptoms and hospitalization early in the outbreak, to about three days more recently.

Still, Aylward expressed frustration at people saying: "'Oh, the mortality rate's not so bad because there's way more mild cases.' Sorry, the same number of people that were dying, still die."