The World Health Organization is seeking clarity from China.

After 15,000 more infections were recorded on Wednesday, 254 more deaths have been confirmed as more than double the previous daily record.

Almost all of them are in Hu Bei province.

Almost 60,000 people in China are now known to be infected on the number of those killed stands at more than 1300.

Also, officials in Vietnam have placed the town of 10,000 people under quarantine following five cases off virus infection there.

Vietnam declared a public health emergency over the epidemic at the beginning of this month.

On in Japan, a cruise ship the Diamond Prince says remains quarantined in Yokohama after an outbreak of the virus on board.

It's now thought 218 passengers and crew members are among those infected.

Our correspondent Rupert Wingfield Hayes is in the port, so the number of infections onboard the Diamond princess behind me here in Yokohama has again jumped today.

44 new cases confirmed today that followed 39 cases yesterday and that brings the total number of infections from the ship to a 218 on that means as we know now, this is now the single biggest outbreak off the cove in 19 virus anywhere outside mainland China.

The Japanese government has made a small concession to the criticism that has bean building off.

It's the way that it's handling this outbreak.

They've said that very elderly people over the age of 80 will be allowed to disembark if they have underlying health conditions or if they're in one of those inside cabins that don't have any outside windows or balcony.

So expect to see that start happening maybe tonight or on Friday.

But there are many questions that remain.

First of all, obviously is.

Are infections still taking place?

Is the virus still circulating around the ship?

No one really knows.

On the other big question is why.

Still, has the Japanese government not managed to test all of the passengers and crew on board?

Well, let's get you some real expertise now.

David Heyman is a professor of infectious disease epidemiology at the London School of Hygiene and Tropical Medicine.

David previously directed the World Health Organization response to the SARS outbreak in 2003.

David First, I want to talk to about the mortality rate the reports were seeing.

I put the mortality rate of this virus at about 2%.

That's right, and that would be at the level of influence seasonal influencing each year they're about when the 2% of people who die unfortunately.

But what's happened in China is the case definition that is, the way they define a disease has included pneumonia, and so they're missing all the less severe cases of disease and only looking at those that are most severe.

So, of course, the mortality is higher among those people.

So the case definition recently has been changed in China, and they're now including less severe symptoms as well in their diagnosis.

On something that's important now is the way they're testing.

It has been to do with these lab kits beforehand on what's been the problem with those Well, they've been using test kits that detect nuclear kassid.

The problem with them is that it takes a long time to get a result longer than they want takes sometimes a day for them to get a result.

Does it something that doesn't require some expertise to administer and and to read absolutely requires both expertise and skill and and making sure that there isn't contamination from the laboratory around it.

So what they've done recently is two things.

They've developed a more rapid point of use test for nucleic acid, which they rolled out.

It's not clear how effective this is, but they're using it.

And in addition, they've changed the way they diagnose.

And in some instances, they're just diagnosing based on symptoms and an X ray, which means there's no nuclear kassid diagnosis.

So does that mean the number off diagnoses?

The number of confirmed cases is bound to jump?

Absolutely.

Because not only are they finding cases of Corona virus, but they're finding other diseases that also other infections.

Rather, it also caused pneumonia, so they're seeing an increase in the number of cases and a decrease in what we call the specificity of diagnosis.

So what in in kind of real world terms, David, what does this mean?

Does it mean that just that the clinicians able to spot Corona virus better or that we should be alarmed at the way in which it is spreading on the rate at which it's spreading well.

Certainly it's spread throughout China, and China is making every effort they can in the way that they do best to stop the disease.

What's important, though, is those 24 sites outside of China and also the cruise ships.

That's where the information about how severe the diseases we really come from, because the patients here are being monitored very closely, as are their contacts.

And we're learning a lot as we see what happens in these situations, which hopefully will lock down the disease in these countries and not permitted to spread further.

Is there an issue here and that China's obviously Communist Party state controlled in a commanding control to a certain extent for other countries, not the case.

And it might be that there's there's less grip on the way centers of run, the ability to build the medical facilities as well.

Well, clearly, in the SARS outbreak, China had the same type of a lock down, and the rapidly got rid of the infection in other countries where there was a different approach.

It sometimes Rickard after they thought they had it controlled.

So there are benefits of authoritarianism, but they're also disadvantages.

And the disadvantages, of course, are an infringement on human rights.

How would you describe your level of concern about the Corona virus outbreak?

I think we're all concerned about what we don't know, right.

We know so far what's happening and what we can see.

But what we don't know is the real potential of this virus, whether or not this eventually could become a disease endemic in humans like TB, influenza or others.

Because influenza also comes from animals into humans and it sometimes becomes a permanent resident.

David Heyman really appreciate you coming in today, Thank you very much.