Yemen's rainy season may trigger another wave of cholera, putting millions at risk in the war-torn country that is still reeling from one of the world's worst outbreaks of the killer disease, scientists warned on Thursday.
More than a million suspected cases of cholera have been reported in Yemen since 2016, and more than 2,000 deaths.The United Nations says 22 million of Yemen's 25 million population need humanitarian assistance.
"We expect to see a surge of cases during the rainy season," said Anton Camacho, lead author of a study on the epidemic published in The Lancet Global Health journal.
"If something is going to happen it will happen now so everyone should be aware and respond quickly. The risk is high," he told the Thomson Reuters Foundation.
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Health authorities should "immediately" boost measures to mitigate risk, an international team urged in The Lancet Global Health.
These could include vaccination, distributing equipment for filtering and disinfecting water, and repairing crumbling sanitation infrastructure.
Based on data from previous outbreaks, the team calculated that 54 percent of districts in Yemen could be affected by an epidemic flare-up in 2018, "totalling a population at risk of more than 13.8 million."
"We thus make an urgent call for action on the part of local officials, donors and international partners, to mitigate the risk of a new cholera epidemic wave in Yemen, which would certainly further weaken a highly vulnerable population."
The rainy season runs from mid-April to the end of August.
The daily number of cholera cases increased 100-fold in the first four weeks of last year's rainy season, leading to the disease spreading across the whole country, the study said.
The authors suggested contamination of water sources during the rainy season and changing levels of zooplankton and iron in water, which help cholera bacteria survive, may have contributed to the explosion of cases.
Cholera, which is spread by consuming contaminated food or water, is a diarrheal disease that can kill within hours.
Yemen's epidemic has been exacerbated by years of conflict, which has damaged health services and water supplies, uprooted more than 2 million people and driven the country to the brink of famine.
The research, which mapped the outbreak and analysed rainfall patterns, has helped health officials and the World Health Organization to identify where to distribute cholera vaccinations.
The scientists said their data also showed a rise in cases after Ramadan, when people often gather for large shared evening meals and also eat more frequently from street vendors.
"We do not want people to think Ramadan brings cholera – that's not the case," said Camacho. "But small behavioural changes in a situation where you have a lot of cholera … can have a huge effect."
Yemen, one of the Arab world's poorest countries, is embroiled in a proxy war between the Houthi armed movement, aligned with Iran, and a US-backed military coalition headed by Saudi Arabia.