Authorities in the Houthi-held Yemeni capital Sanaa are sterilising water supplies at wells, distribution networks and houses to help stem the world's worst outbreak of cholera.

Key points: Cholera is a diarrheal disease spread through food and water, killing within hours

Cholera is a diarrheal disease spread through food and water, killing within hours WHO says cases are accelerating compared to 2018 averages

WHO says cases are accelerating compared to 2018 averages With 1.8 million children already malnourished, authorities fear fast outbreak

Nearly four years of war between a Saudi-led coalition and the Iranian-aligned Houthi group have crippled healthcare and sanitation systems in Yemen, where 1.2 million suspected cholera cases have been reported since 2017, with 2,515 deaths.

Cholera, which is spread by consuming contaminated food or water, is a diarrheal disease and can kill within hours.

The World Health Organisation (WHO) warned in October the outbreak was accelerating again with roughly 10,000 suspected cases now reported per week, double the average rate for the first eight months of 2018.

Most cases have been reported in areas held by the Houthi movement, which controls most population centres after ousting the internationally recognised government from Sanaa in 2014.

"We receive information of reported cases of cholera from the Ministry of Health, then the team sterilises the house and 20 houses around it," said Nabeel Abdullah al-Wazeer, the Houthis' diarrheal disease minister of water.

"We worked from house to house and on sterilising water wells. We also worked on bus-mounted tanks, which transport water in the private sector to the citizens, as well as sterilising local institutions which distribute water."

Adel Moawada, director general of technical affairs at Sanaa's main water sanitation plant, said there were 20 automated chlorination units installed in wells directly linked to the capital's water distribution network.

Malnutrition has weakened immunity to cholera

UNICEF estimates 1.8 million Yemeni children are malnourished. ( AP: Hani Mohammed )

While previous outbreaks may have helped build immunity in the population, other diseases and widespread malnutrition can weaken resilience.

The United Nations says about 14 million people, or half of Yemen's population, could soon face famine, while UNICEF estimated 1.8 million children were malnourished.

Children account for 30 per cent of cholera infections.

Pediatrician Mohammed Abdulmughni administers intravenous fluids to children in WHO tents in Sanaa.

Their beds rest on gravel and flies circle their faces.

"With winter's arrival we expected the numbers would decrease, yet the cases have been coming in at the same pace," he said.

"We expected positive [diagnoses] cases to decrease but the cases remain high."

If caught early, acute diarrhea can be treated with oral hydration salts, but more severe cases require intravenous fluids and antibiotics.

More than 250,000 cases of cholera have been recorded in Yemen since the beginning of 2018, with 358 associated deaths, reported UNICEF representative Meritxell Relano.

"We have prevented an outbreak at the scale of 2017," Ms Relano said. "But the risk is still there."

Reuters