bnsf railway. and by the bill and melinda gates foundation, dedicated to the idea that all people deserve the chance to live a healthy, productive life. and with the ongoing support of these institutions and foundations. and this program was made possible by the corporation for public broadcasting and by contributions to your pbs station from viewers like you. thank you. >> brown: victims of the great flood in pakistan protested today over lack of aid. they blocked a main highway in the south, even as fresh flood warnings were issued along the indus river. meanwhile disease began spreading among refugees in makeshift camps. we start with a report from special correspondent in pakistan. >> this is a disaster of an unimaginable scale. mile after mile all you can see is water and the devastation it has caused. so powerful that it took people, livestock, roads, bridges and entire villages with it. one million , about 28 million liters per second is making its unforgiving way to the southern part of pak