Pakistan flood surge moving south

Emergency crews are still trying to assist people in flood-ravaged northwestern Pakistan, while officials are warning people in the south to brace for floods and an outbreak of disease that may follow.

The floods have already killed an estimated 1,500 people over the past week, and as many as four million people have been affected by the floods, which tore through villages, swallowed homes and destroyed crops.

"It is a catastrophe, there's really no other word for it," Joseph Prior, a field co-ordinator for Doctors Without Borders, told CBC News.

Much of the damage was concentrated in the country's northwest, which has not seen such devastating floods since 1929.

Aid workers and government officials have struggled to deliver aid as water and mud devastated local infrastructure.

Four U.S. army helicopters arrived in the area Thursday to help transport people who had been stranded by the floods. A U.S. Embassy spokesman told The Associated Press that 800 people were lifted out and relief goods distributed.

Manuel Bessler, the United Nations humanitarian chief in Pakistan, told reporters "we are facing a disaster of major proportions."

"Even a week after the disaster we don't have all the details. Roads are washed away. Bridges are destroyed. Whole areas are completely isolated and only accessible by air."