Shahdadkot, Pakistan (CNN) -- The misery of Pakistan's flooding, which has already displaced millions, is showing up in the form of communicable illnesses, the United Nations said Monday.
Up to 1.5 million flood victims in Pakistan were being treated for a variety of ailments and conditions, including acute respiratory infections, diarrhea and skin infections, according to Maurizio Giuliano with the U.N. Office for the Coordination of Humanitarian Affairs.
Prime Minister Yousaf Raza Gilani has called a Tuesday meeting of senior Pakistani health officials, local officials, U.N. agencies and other international group to look into the emerging health crisis, state-run TV reported.
The World Health Organization announced Sunday that cases of acute diarrhea have topped 204,000. The number of skin diseases -- such as scabies -- has topped 263,300.
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More than 204,600 Pakistanis have reported acute respiratory infections as filthy waters surround homeless flood victims, WHO said.
Thousands have cases of suspected malaria.
"Strong water and sanitation interventions, such as providing clean drinking water supply and addressing environmental hazards, are urgently needed to prevent outbreaks of waterborne diseases in" Charsadda, Nowshera and Peshawar, WHO said.
Meanwhile, the half-million residents of Shahdadkot frantically tried to flee their homes over the weekend as a wall of water threatened to burst mud berms and drown the entire city in Pakistan's Sindh province.
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.
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.
"The depth of suffering is incalculable as risks escalate of diarrhea, acute respiratory infection, malaria and other communicable diseases," said Dr. Guido Sabatinelli of the World Health Organization. "It is crucial that all humanitarian health providers, local and national, coordinate their relief efforts closely to save lives, reduce suffering and deliver the most effective response."
WHO said waterborne, airborne and vector-borne diseases, including acute watery diarrhea, measles, malaria and acute respiratory infections, are threats due to overcrowding, lack of hygiene and breakage in waterlines.
The focus is now turning to heading off more disease, particularly among young children, WHO said.
More than 100,000 children have been given polio shots in Charsadda and Peshawar regions in the first three days of a new vaccination program.
United Nations officials have appealed for $460 million over the next three months to help the roughly 20 million people in need of shelter, food and emergency care.
Meanwhile, International Monetary Fund officials said they will meet with members of the Pakistani government in Washington next week to discuss the economic impact of the massive floods that have ravaged the country.
"The floods, which have hit Pakistan in recent weeks and brought suffering to millions of people, will also pose a massive economic challenge to the people and government of Pakistan," said Masood Ahmed, director of IMF's Middle East and Central Asia Department.
Ahmed says the meeting will be an opportunity to evaluate the economic impact of the floods, assess what Pakistan's government is doing to respond to it and "discuss ways in which the IMF can assist Pakistan at this difficult juncture."
