A hygiene specialist for UNICEF in Solomon Islands says the first cases of malaria, diahorrea and respiratory illness have been confirmed in evacation centres following last week's devastating floods.
At least 23 people have died and thousands of people have been displaced from their homes.
Donald Burgess says children are the most vulnerable to disease outbreaks.
He says providing clean water and sanitation in camps is a priority to avoid further casualities.
"A lot of people who are in the camps are having diahorrea, the reports are coming from there, and malaria. And if it is not being tackled speedily and urgently the situation may deteriorate further."
Donald Burgess says more help is needed to avoid a disease toll worse than the disaster itself and doctors have been seconded to some of the larger camps.