. tonight an unseen enemy has potential to unleash a global health crisis. there's a growing threat from infectious diseases and a deadly pandemic. take a look. >> the last three decades there have been about 30 newly emerging diseases that had the potential to be pan democratics. if we do nothing, it's not a matter of if there will be a global pan democrat irk, it's just a matter of when. which virus, and how bad. >> the world changes around us at increasing speed. we caused a lot of that change. migrating to cities, stripping the earth of its resources, and