Disease could double the death toll from the tsunami that hit the Indian Ocean region at the weekend, a top World Health Organization (WHO) official said on Tuesday.

Dr David Nabarro told a news conference it was vital to rush medical treatments and fresh water to the worst-hit countries in order to prevent a further catastrophe.

“There is certainly a chance that we could have as many dying from communicable diseases as from the tsunami,” Nabarro said.

The death toll from the tsunami that was triggered by a massive earthquake has passed 59,000, but is still rising. The worst affected countries are Sri Lanka, Indonesia, India and Thailand.

Nabarro, head of the Geneva-based U.N. agency’s heath crisis team, said it was essential to get health systems back up and running and send in medical teams from abroad where needed.

“The immediate terror of the tsunami may be dwarfed by long-term suffering in the affected countries where the risk of widespread disease is very high,” he said. “The main thing we have to worry about is the lack of clean drinking water or the contamination of what water there is through leakage of sewage into distribution systems.”

There was a serious risk of an explosion of malaria and dengue fever, already endemic in southeast Asia. Respiratory infections like pneumonia could also spread fast among homeless people crowded into temporary shelters.

“So our focus has to be on saving lives, preventing disease and doing all we can to ensure the rapid recovery of public health systems,” Nabarro said.

RECORD APPEAL

Speaking at the same news conference, Yvette Stevens of the U.N. Office for Coordination of Humanitarian Affairs (OCHA) said she expected a global appeal for funds to be the world body’s biggest.

The previous largest sum requested for disaster relief was $350 million after the Bam earthquake in Iran that struck on Dec. 26, 2003, exactly a year before the Indian Ocean catastrophe, and killed some 30,000 people.

U.N. officials say the tsunami is the biggest natural disaster it has faced in its 60 years.

Giant waves roared across the Indian Ocean, wiping out entire communities on islands in the Bay of Bengal and Indonesia’s Aceh province and killing people as far away as Somalia and Kenya.

Stevens, who heads OCHA’s Geneva office, said an initial appeal was expected in the next two or three days when assessment teams had reported back, with a more detailed funding program to be launched by mid-January.

A list of offers pledged so far by donor countries showed at least $80 million was already in the pipeline.