A Kuwaiti health official says all 18 U.S. soldiers infected with swine flu have recovered and left this oil-rich U.S. ally. The official, Youssef Mandakar, said Sunday the soldiers entered Kuwait by air and didn't have any contact with the local population. He said their cases were ''mild'' and they have all left the country. He wouldn't say where they came from or their destination. Kuwait announced Saturday that a number of American soldiers passing through the country were infected, but it didn't say how many. The U.S. Embassy and the military also had declined to give any details other that they were being treated. Kuwait is a major ally of Washington and a logistics base for U.S. military personnel serving in Iraq.