Fears that the Indian Ocean tsunami could unleash epidemics that would double the death toll are fading as access to clean water improves, the World Health Organisation (WHO) said on Thursday.

Over 158,000 were killed, most of them in northern Indonesia and Sri Lanka, by huge waves sent crashing across the ocean after an undersea earthquake on Dec. 26.

The U.N. health agency warned last week a similar number could succumb to diseases.

But the biggest global relief effort seen in peacetime is reducing the health threat, particularly from water-borne disease, although there is a need for continued vigilance, WHO spokesman Iain Simpson told Reuters.

“The risk of large numbers of fatalities from disease is beginning to fade ... I do not think we are looking at potential death from disease to match the tsunami,” he said.

Most people in the affected area, which stretches from Indonesia to Somalia on the Horn of Africa, had access either to clean water or to water purification tablets.

“The threat of water-borne diseases is easing, even if it has not disappeared entirely, and that was something that we pointed out as a concern in the early days,” he said.

But sicknesses spread by mosquitoes such as malaria were still a worry, as was the overall health situation of tens of thousands of people in outlying areas of the Indonesian province of Aceh where information was scarce, Simpson added.

Malaria already exists in Indonesia and Sri Lanka and the WHO has launched a campaign with local health authorities to prevent any major outbreaks, he said.

The disease is not so widespread as in Africa, where it is a major killer, because many more people use bed nets, one of the most effective means of prevention.

But the mosquito nets have gone along with the houses destroyed by the earthquake and tsunami, Simpson said.

The United Nations has already raised some 70 percent of the near $1.0 billion that it has sought to feed, clothe and provide medicine for people in stricken areas over the next six months.

The WHO has received $35-40 million of the $67 million it requested as part of the U.N. appeal, Simpson said, adding this was enough to finance immediate operations.