Three weeks into the worst natural disaster in Pakistan's history, people were still desperate to escape as a second wave of monsoon floodwaters surged southward. More than 1,500 people have died and 20 million lives have been disrupted. Authorities advised the entire population to evacuate.

Floodwaters are expected to recede in the next few days as the last surges in the Indus River flow into the Arabian Sea. But the suffering is sure to continue. Health officials fear that the human toll will get a lot worse as people are forced to wade through unsanitary water while clean drinking water is scarce.

More than 200 health facilities have been damaged or destroyed, according to the World Health Organization, greatly reducing the available health care for millions of survivors in filthy conditions. At least 4 million people are homeless.

Dr. Guido Sabatinelli of the World Health Organization said reports of diarrhea have increased 30 percent. WHO said waterborne, airborne and contagious diseases, including acute watery diarrhea, measles, malaria and acute respiratory infections, are threats due to overcrowding, lack of hygiene and breakage in waterlines.

United Nations officials have appealed for US$460 million over the next three months to help the roughly 20 million people in need of shelter, food and emergency care.