Cholera cases in Yemen could quadruple in the next month to 300,000, the regional director of Unicef said Friday, calling the spread of the disease in the war-ravaged country “incredibly dire.”

Speaking by phone after visiting Yemen, the agency’s regional director, Geert Cappelaere, said he had never seen a cholera outbreak of that size in the country, which already is contending with the risk of a famine and a collapse of the health care system because of the war.

Half the cholera cases in Yemen belong to children, Mr. Cappelaere said, and parents have little recourse because many hospitals and clinics are closed or lack supplies.

Mr. Cappelaere, who was named Unicef’s director for the Middle East and North Africa last year, worked for the agency in Yemen from 2009 to 2012. This was his first trip since then back to the country, poorest in the Arab world.