BY Nick Triggle
BBC News health reporter
With 23,000 people dead and more than 1m made homeless by the South Asian earthquake, fears of disease have been raised.
Only two thirds of children are immunised against measles
Health officials and aid workers on the scene have warned unless fresh water and food are made available potentially-deadly diseases such as cholera, plague and diarrhoea-related illnesses will take hold.
Leyla Berlement, an International Committee of the Red Cross official based in Pakistan, said Saturday's 7.6 magnitude quake had cut whole towns and
"There will be no fresh water and no food. Our fear is that diseases such as cholera will take hold as people become desperate.
"The risk is that they will have to drink contaminated water. Medical help is needed if the situation is not going to get worse. But many of the areas are very difficult to reach."
And the World Health Organization said it was worried about malaria and measles, which is already endemic in the region.
A spokesman said with only two thirds of children protected, officials were preparing a mass immunisation programme.
But less than a week after the disaster, other diseases have already started taking hold.
Irfan Ahmed, a doctor with the British-based charity Plan, who has been helping people in Pakistan's Northwest Frontier Province, said gangrene and diarrhoea were spreading.
"People are getting gangrene as they are not getting medical help.
"And one problem is diarrhoea because the water supply has gone out and the people are drinking whatever they can."
This is not the first time outbreaks of disease have been warned about following natural disasters.
In the aftermath of the South Asia tsunami, experts predicted the death toll from disease could dwarf those killed by the wave.
Deaths on such a scale did not materialise, neither did they following Hurricane Katrina last month.
But some predict this time it will be different.
Dr Ron Behrens, a disease expert at the London School of Hygiene and Tropical Medicine, said: "In the case of the US people were, eventually, removed from the area so disease never took hold.
"With the tsunami, what is interesting is that while many people died initially, it did not damage the infrastructure such as water supply and sewage disposal to the scale this earthquake may have.
"The really important factor is this environmental health. Is there clean water to drink? Is sewage disposed off?
"I would expect there to be a lot of disruption to this infrastructure and that could lead to cholera and diarrhoea.
"Insects are also likely to thrive in this environment, although it maybe too cold for malaria to take off. Plague is also a concern.
"The key is getting clean water to people and getting rid of sewage, it will be a hard task."