From this Guardian story, writer Declan Walsh gives us the latest update from Pakistan.
Aid agency Plan International worries the figure will surpass 2m. "The most vulnerable are women and children," said its Pakistan director, Haider Yaqub.
The malaria threat is part of a wider health emergency, with more than 20 million people affected by the floods struggling to cope as the winter approaches.
Last night the UN reported 881,000 cases of diarrhoea, 840,000 cases of skin diseases and almost 1m cases of respiratory disorders. Dr Dana van Alphen of the WHO said: "There are no epidemics yet – it's not Goma in 1994. But we have to be very careful."
Increasing UK aid to £134m recently, the international development secretary, Andrew Mitchell, warned of extremely serious public health dangers.
The floods have devastated Pakistan's flimsy public health system. More than 500 clinics have been damaged, while the government estimates that 30,000 "lady health workers" – a programme that is the backbone of the community health system – have been made homeless.
Pregnant woman are a particular concern. An estimated 50,000 flood-affected woman will give birth in the coming month, 7,500 of whom will require surgery for pregnancy-related complications.