A case of the deadly waterborne disease cholera has been confirmed in Pakistan’s flood-ravaged northwest, and aid workers expect there to be more, the U.N. said Saturday. The discovery came as new flood surges hit the south and the prime minister said the deluge has made 20 million people homeless.

The flooding disaster has battered Pakistan’s economy and undermined its political stability at a time when the United States needs its steadfast cooperation against Islamist extremism. The U.N. has appealed for an initial $460 million to provide relief to Pakistan but has said the country will need billions to rebuild once the flood recedes.

Because of the crisis, Pakistan canceled celebrations Saturday marking its creation and independence from Britain in 1947. President Asif Ali Zardari met with flood victims in the northwest, and U.N. Secretary-General Ban Ki-moon was expected to visit country soon, possibly over the weekend.

The floods have killed about 1,500 people, and aid workers have warned that diseases could raise that toll.

Bloomberg