There are concerns the bird flu virus could mutate

Thomson Prentice, editor of the WHO's annual report - speaks to the BBC about the nature of the problem and explains what needs to be done.

What is it about modern life that makes the international spread of disease such a risk?

With something like two billion passengers travelling last year, that works out at something like three million people every day flying from one city or one country or one continent to another. The potential, I think, is obvious for someone with an infectious disease unwittingly perhaps carrying it from one part of the world to another.

Can you give any specific examples of what countries need to be doing more of to improve rapid response to spreading disease?

It's certain that there will be, sooner or later, a flu pandemic - if it isn't flu, there's always going to be a new disease sooner or later that we don't know about Thomson Prentice World Health Report managing editor

One of the things they need to do is realise that they can't keep secrets any more. The idea that you might have an outbreak of an infectious disease that could be damaging to the image of the country, or to the tourism of the country, or to the country's economy, that cannot be kept quiet any more. So we're asking countries to recognise that nothing today travels faster than information, and if they don't report it someone else will, either officially or unofficially. And it's WHO's obligation to respond to information as promptly as it possibly can.

How big are the holes in international strategy currently?

The holes are largely to do with economics. The poorer countries of the world, largely in sub-Saharan Africa, also in many parts of Asia and elsewhere, those are where the real gaps are and what the international community has to do is to try to support those most in need. It's another side of the poverty argument - where poor countries need help is in building up their health systems, in order to deal with some of the threats to health that, first of all, endanger their population, but if they're not well controlled and dealt with, threaten populations elsewhere.

What is the worst case scenario? What could be the repercussions if countries don't implement sufficiently the regulations that the WHO is trying to put in place to contain diseases?

The worst case scenario is a pandemic of a disease such as influenza which spreads rapidly and out of control, going from person to person and from country to country with inadequate supplies of drugs or vaccines to deal with it, with a large number of deaths and a huge number of cases of illness, and beyond the human cost gigantic economic costs and disruption.

How likely is that?