UNICEF in Solomon Islands says more help is needed to avoid further casualties from disease, as the first cases of malaria, diarrhoea and respiratory illness are confirmed in evacuation centres following last week's devastating floods.
At least 23 people died in the floods and thousands have been displaced from their homes.
Hygiene specialist Donald Burgess told Radio New Zealand International a lot of people in the camps had either diarrhoea or malaria.
He said these illnesses needed to be addressed quickly. "And if it is not being tackled speedily and urgently the situation may deteriorate further."
Damage to main water reservoir
Solomon Islands authorities say damage to a main water reservoir following the flooding means they are having to look for alternative sources.
National Disaster Management Office director Loti Yates said donor agencies were hiring water tanks and delivering them to communities around the capital Honiara.
He said the Solomon Islands Water Authority was working on improving the water systems but its assessment has revealed problems.
Mr Yates said some damage to the main source in one of the reservoirs had been found and they wanted to make emergency repairs to water supply sources and to look at alternative water sources.
He said water was currently being taken from functioning reservoirs and then taken to areas in need.
Funerals still taking place
Funerals are still taking place after the flash floods that killed at least 23 people.
The ABC reports floods swept away entire residential districts, leaving thousands of people homeless. Work has begun to repair key bridges.
Uniting Church minister Cliff Bird said almost half of those killed in flash floods were children and many people were still traumatised.
He said local church groups had been helping to feed about 9000 people in camps and he said more homeless people were staying with friends and families.
Queen Elizabeth II has sent condolences to the government and people of Solomon Islands.
In a message to the Governor-General, Sir Frank Kabui, the Queen said she was deeply saddened to learn of the floods.
She said Prince Philip joined her in sending heartfelt condolences to the friends and families of those who died and good wishes to all those involved in the emergency response and the reconstruction process.
World Vision staff distributing clean water. Photo: AFP / WORLD VISION / Rachel Skeate
