could make an H5N1 epidemic a more sweeping public health emergency than the world has ever faced.

Second, and perhaps more important, is the fact that “H5N1 is a wakeup call.” The H5N1 threat raises questions of how the virus has had the opportunity to spread globally as quickly as it has, how novel this threat may be, and what potential exists for other zoonotic diseases to emerge in the same way. Carroll presented a list of infectious diseases and pathogens that have emerged since 1973, shown in Figure 2-1, to demonstrate the scope of the potential threat posed by zoonotic diseases.

These newly identified diseases have emerged primarily as a result of significant changes in human activity, including population growth, increased demand for animal protein, increased wealth and rapid travel by people and their animals, changes to the environment, and human encroachment on farm land and previously undisturbed wildlife habitats. Other pathogens could follow a similar pathway. Thus, Carroll explained, it is very important for policy makers to understand the kind of surveillance and action that will be needed to protect the public and the benefits they provide, and it is up to the scientific and public health community to make this case. He suggested that the current status of global surveillance systems

FIGURE 2-1 Infectious diseases and pathogens newly identified from 1973–2004.

SOURCE: Carroll (2008).