With a whirlwind of mosquitoes around his head, Aamir Hussain stands on the roof of his house in southern Pakistan, observing the foul-smelling floodwaters all around.

Four months after record monsoon rains hit the country, the standing water has thickened into a deadly soup breeding cholera, malaria, and dengue.

Warnings of a "second wave" catastrophe have been spread by the UN, including the risk of deaths due to water-borne disease and malnutrition which will overcome the number of those who drowned or died as a result of electric shock in the initial floods.

Read: UN expects situation to worsen in Pakistan due to floods

Hussein lives in the submerged village in Dadu district in Sindh province, where bugs appear in the night and fears grow that they might infect his wife and two children.

He shares his home with his brother, who has ventured off the roof and has been treating his sick children at the hospital with money he had borrowed.

"Some of our nets are torn now so we are worried," Hussein told AFP, whose baby has fallen ill.

Sindh has been the worst hit by the deadly flooding which put a third of Pakistan underwater, displaced eight million individuals, damaged two million houses, crippled 1,500 hospitals, and clinics, and caused damages valued at an estimated $28 billion.

"Urgent medical services" are needed for those eight million displaced, according to Zahida Mallah who just cannot cope anymore with the situation.

The 35-year-old said she was mourning her twin two-month-old sons, who were killed by "colds" after they had to sleep out in the open. The tent she was offered was not helpful, as it came too late. "We just keep floundering," she lamented.

Nearby, the city of Johi is filled with water and is only accessible by a ramshackle flotilla of canoes. However, the city cannot keep the disease away. In a desperately rundown emergency clinic, a doctor treats 7-year-old Kashaf on dirty sheets. The patient is unresponsive and is suspected to have malaria.

"From early evening until dawn, throughout the whole night, the mosquitoes are overwhelming," said 19-year-old Kashaf's mother, Bashiran Mastoi.

"When the night approaches we start to worry." "Life at the camp is immensely miserable," she said in a vigil on her child's sickbed.

Medic Manzoor Shahani said there has been a "surge" in malaria, gastro illnesses, and dengue, while "most of the patients are children and pregnant women".