The United Nations warned Wednesday that its programs to fight the coronavirus in war-torn Yemen might have to stop by the end the month unless they get an immediate injection of cash. The warning comes a day after a U.N. appeal for countries to fund emergency aid in the Arab world’s poorest nation fell a billion dollars short of what aid agencies needed — $2.41 billion — to cover essential activities from June to December. “This will severely handicap efforts to contain the outbreak, which is already spreading rapidly,” said Hayat Abu Saleh, a spokesperson for the U.N. Officer for the Coordination of Humanitarian Affairs.