The World Health Organization says global cooperation on reporting possible bird flu outbreaks in humans is crucial. A senior WHO official says it is possible a pandemic could be stopped, if detected and dealt with early enough.

A deadly strain of avian flu, also known as bird flu, has led to the deaths or slaughter of tens of millions of poultry, and has spread from Asia to Europe through migratory birds. The virus is blamed for the deaths of about 60 people, mostly in Asia, but health experts warn that it could spark a pandemic, if it mutates into a form that can spread easily among humans.

WHO official Michael Ryan says he believes it will take at least another six months to a year to ensure that there are adequate and responsive surveillance systems in developing countries.

"The reality is that, in many countries, surveillance systems are weak," he said. "We need to know when this pandemic virus emerges, and we need to know quickly. We need to know, to give the rest of the world lead time. We need to know, so we can get the virus itself, to [so we can] start producing the vaccines."

Mr. Ryan told the NBC television program, Meet the Press, that, with enough early warning and very rapid response, there is a small possibility of throwing a "fire blanket" on the virus that would smother it and keep it from spreading.

"Well, there is some evidence, and again, there are some uncertainties here, but there is some evidence that, if we were to detect the emergence of a pandemic strain early enough, some [study] models suggest that, with the application of social distancing, or quarantine-like measures, and the rapid distribution of anti-virals in that population, we may be able to significantly slow down, or stop the emergence of a pandemic strain," added Mr. Ryan.

The possibility that a pandemic will definitely occur is a topic for debate. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, acknowledged that it is not inevitable that the current H5N1 strain of bird flu will mutate into a virus that easily transmits from human-to-human. But, he said, it is still important to be prepared.

"We can't put a number on how probable that's going to be [that the virus mutates into a pandemic]. Likely, it's a low probability," he said. "But when you're dealing with preparing for something, in which the consequences are unimaginable, you must assume, a) the worst case scenario, and, b) it's going to happen."

The WHO's Dr. Ryan urged governments not to balk at what he described as the "large investment" they will have to make for a global health surveillance system, which could be used for other deadly viruses, as well.

"But the benefit of such an investment, even if the pandemic does not come, the benefit is we will have a stronger public health system to pick up the next SARS, to pick up the next Ebola, the next Marburg, or the next West Nile [virus]," he added.

Dr. Ryan said the possibility of an avian flu pandemic is serving as a warning to the world that, in terms of global health security, it is vulnerable. This, he added, is why he is calling for better developed global systems to detect and contain new viruses.