Many infectious diseases have originated as animal diseases that are transmitted to humans. For some diseases, the nature of the disease-causing organism may lead to widespread transmission in humans and cause a global disease outbreak, or pandemic, resulting in many deaths.

The United States is concerned that the ongoing outbreaks of H5N1 avian influenza in birds, or bird flu, have the potential to turn into a human influenza pandemic. Whenever or wherever a pandemic begins, everyone around the world will be at risk.

To fuel a pandemic, a virus must be able to easily spread from person to person. And although currently the H5N1 virus does not spread easily from human to human, its mortality rate in humans is so high-over 60 percent-that we cannot take the chance that it will not do so in the future. Several influenza pandemics have occurred during the last century. The pandemic in 1918-1919 spread to every continent, and caused at least 40 million deaths world wide.

The effects of a pandemic can be lessened if preparations are made ahead of time. Working through the International Partnership on Avian and Pandemic Influenza, the U.S. Government and others in the international community have developed national and international programs to prevent, detect, and limit the spread of the avian flu virus.

Central to that effort is building infrastructure, including laboratory capacity and international rapid response mechanisms; a global surveillance and warning system; a coordinated plan of intervention; and of course, the development of vaccines. The U.S. has pledged $ 949 million in support of these efforts.

Preparing for a pandemic is difficult but necessary. "We need to maintain our sense of urgency with respect to the pandemic threat if the momentum of preparedness and capacity building is to be maintained," says Ambassador John Lange, Special Representative on Avian and Pandemic Influenza for the U.S. Department of State.

"Capacity building doesn't garner headlines, but the threat persists and large-scale injections of resources and energy are still needed to prepare for and respond to a potential pandemic."