The United Nations voiced concern on Wednesday after dozens of cases of cholera were reported in flood-stricken Kenya.

The World Health Organization (WHO) said 44 cases of the disease have been reported in Tana River County in eastern Kenya, one of the areas hardest hit in weeks of destructive rains and flooding.

"I believe that between government and national and international partners, we'll be able to contain it," the UN's resident coordinator in Kenya, Stephen Jackson, said in an interview with Citizen TV.

"We've contained cholera before, but it's a significant concern," he added.

Cholera is an acute intestinal infection that spreads through contaminated food and water and typically causes severe diarrhoea, vomiting and muscle cramps.

It can be especially dangerous for young children.

"WHO will continue to support the health emergency response and remain vigilant for disease outbreaks that can easily spread if not quickly contained," Abdourahmane Diallo, WHO representative in Kenya, said in a statement issued by the UN's health agency on Tuesday about the 44 cases.

"We must be agile and ready to respond, led by government and along with the partners, to bring relief to hundreds and thousands of affected people," Diallo said.

- Schools to reopen -

The flooding in Kenya has killed 238 people since March, according to latest government figures published by the local media, while 75 are still missing.

Across the country more than 235,000 people have been displaced as floodwaters and mudslides engulfed homes, roads and bridges.

But President William Ruto announced on Wednesday that schools would reopen next Monday after a two-week delay, saying the rains had now subsided and it was safe for children to return to class.

He also declared that Friday would be a public holiday to remember those lost in the floods and to kickstart an extensive tree-planting programme in the country.

Ruto, who has positioned himself at the forefront of African efforts to combat climate change, has blamed the region's calamitous cycle of drought and floods on a failure to protect the environment.

- 'Alarm' over looming drought -

Overall, the heavier than usual seasonal rains, compounded by the El Nino weather phenomenon, have claimed the lives of more than 400 people in East Africa, a largely poor region highly vulnerable to climate change.

Late last year, more than 300 people died in rains and floods in Ethiopia, Kenya and Somalia, just as the region was trying to recover from its worst drought in four decades that left millions of people hungry.

And the UN's Jackson warned that there was a "significant risk" of another drought, according to long-range forecasts.

"So it's a point of alarm. It's not yet a certainty. What is a certainty is, given the climate crisis, that there will be a drought along again this year or next year or the year after," he said.

"We know that these are coming harder and harder and faster and faster."

Meanwhile, all residents of a five-storey apartment block on the edge of the Kenyan capital that collapsed on Tuesday night are safe, a local official said.

"All tenants are accounted for, including the four missing persons initially reported," Nairobi's chief officer for disaster management, Bramwel Simiyu, said in a statement.