ADEN, Oct. 14 -- At the diarrhoea treatment centre in Aden's AlSadaqah Hospital, a mother sits beside her child's bed. The centre is supported by the World Health Organization and the Saudi aid agency KSrelief, and suspected cholera cases in Yemen have tripled in three weeks.

Suspected cholera cases rose from 217 in the week of Sept. 6 to 12 to 647 in the week of Sept. 27 to Oct. 3, the WHO said on Tuesday. Yemen has reported 8,034 suspected cases and 27 deaths this year, and a quarter of those cases came in the last four weeks.

The driver is displacement, and the need is money. Fighting that escalated on Aug. 6 has displaced more than 200,000 people across 10 governorates, many into camps with little safe water. Five south-western gove...