Floodwater destroyed houses and swept away property and vehicles as the capital Freetown, an overcrowded coastal city of 1.2 million mainly poor inhabitants, was pounded by torrential rain on Wednesday last week.
The official toll has risen to 10, according to government officials coordinating the clean-up, while an estimated 9,000 survivors were sheltering in tents in the national stadium and another smaller sports arena.
At least 20 neighbourhoods were flooded by the five-hour storm, according to a statement from the presidency, while the city's main hospital was inundated.
It rains six months of the year in Freetown, one of the world's wettest cities, and putrid water from its populated slopes inundate its coastal slums every summer.
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The Ministry of Health warned of the heightened risk of waterborne disease such as cholera that would come with the flooding, vowing to provide 24-hour free healthcare for the sick.
The flooding came with Sierra Leone close to eradicating an epidemic of the tropical Ebola fever which has killed more than 11,000 in west Africa since December 2013.
"So far, there is no scare and nobody has shown any signs and symptoms of Ebola," said NERC spokesman James Bangura.
"However, since many of the people are from slum areas where Ebola was prevalent... We are monitoring the situation closely."
Freetown residents said they had never experienced rain as heavy as last week's downpours.