The consequences from severe flooding in Kenya could last beyond the current heavy rains, with environmental damage raising the risks of contamination and disease.
"Many water sources are polluted and the risk of epidemics spreading throughout the country is increasing," said Camilla Schynoll, emergency relief coordinator for the German aid agency Welthungerhilfe.
"It's a race against time," said Schynoll. "The poorest and already vulnerable families in particular urgently need safe shelter and access to basic services such as clean water, food and health clinics."
The floods are currently causing a fourth cholera outbreak, she said.
As of Wednesday, 257 people had died in Kenya during the rainy season storms alone, while the search continues for more than 70 missing persons.
Kenyan President William Ruto has declared Friday a national holiday to commemorate the victims of the floods.
Last year, the El Niño weather phenomenon also triggered flooding and destroyed houses, roads and agricultural land with heavy rainfall, particularly in regions that are usually characterized by drought.
"The destruction caused by the last floods has not yet been fully repaired and many people have not yet been able to completely rebuild their homes. And now the next tragedy is occurring and there is no end to the rainfall in sight," said Schynoll.
"This time, the urban areas are badly affected, where many people already live in cramped conditions and in very poor conditions," said Schynoll about the rains, which were extreme in the greater Nairobi area.
The floods were particularly tough on low-wage workers who could not evacuate, as they depend on meagre incomes for their subsistence: "Many of the slum dwellers are day labourers and live hand to mouth."
There is a continued risk of further landslides, especially in hilly areas, due to soil softened by the heavy rains.