"Standing water can be just as deadly as moving water," said UNICEF Executive Director Carol Bellamy. "The floods have contaminated the water systems, leaving people with little choice but to use unclean surface water."
Although relief organizations have begun distributing medical supplies to prevent disease outbreak around the 11-country arc hit by the Indian Ocean tidal waves, the main focus is still on dealing with the wounded, said Jamie McGoldrick, an emergency relief coordinator of the U.N. Office for the Coordination of Humanitarian Affairs in Geneva.
"We're incredibly worried right now also about the water-borne diseases — things like malaria and cholera. That could make this emergency as it is even greater," CARE's Heather Simpson told CBS Radio News.
During a State Department briefing on Wednesday Lt. General James T. Conway told reporters that U.S. military personnel and supplies have been rerouted to the Indian Ocean with relief material including several ships that can purify water.
"Each ship can produce 90,000 gallons of fresh water a day and, of course, that will be extremely valuable as we have a number of requests already for fresh water supply," Conway said.
The most immediate need is also the most basic: clean drinking water, reports CBS News Correspondent Lee Cowan. Sources have either been contaminated with bacteria or massive amounts of seawater. The short-term fix is to send bottled water, but a long-term fix would be to send water purification systems. The components are available, but what is lacking is the money to ship it."
It is still impossible to visit some isolated islands off the northern coast of Sumatra and assessments can only be made from the air, OCHA's McGoldrick said.
"Populations we haven't reached yet may suffer from disease," he said.
With relief officials warning of possible cholera epidemics and malaria, Dr. David Nabarro, head of crisis operations for the World Health Organization, has said that "there is certainly a chance that we could have as many dying from communicable diseases as from the tsunami."
Nabarro said the main threat to life now is communicable diseases associated with a lack of clean water and sanitation.
"The initial terror associated with the tsunamis and the earthquake itself may be dwarfed by the longer term suffering of the affected communities," he warned.
Hospitals and health services already are overwhelmed and may not be able to cope with people who fall ill with disease, Nabarro said.
Worst hit have been Indonesia, Sri Lanka, India, Thailand and the Maldives. But Malaysia, Myanmar, Bangladesh, Somalia, Tanzania, Seychelles and Kenya have also reported deaths from the tidal wave that sped across the Indian Ocean Sunday morning.
The United Nations has sent disaster assessment teams to the affected countries and relief organizations are distributing supplies. The global body is also starting to put together an appeal for international aid.
Essential supplies are already arriving in the region, but "need to be properly coordinated so that those who most need help get it in these vital early hours and days after the disaster," Nabarro said.