The San Diego Union-Tribune said Hawaiian Airlines flight 15 from San Diego to Hawaii last Saturday included a infant who contracted the illness in a San Diego medical clinic. The child is being treated on a military base in Hawaii.

Dr. Wilma Wooten, San Diego County's public health officer, said officials are most concerned about children who have not been immunized.

The outbreak began when a 7-year-old returned to San Diego from a family vacation in Switzerland Jan. 15 infected with measles, the newspaper said. The 7-year-old set off a chain reaction that has infected two siblings and at least one classmate.

San Diego County health officials said they've confirmed measles in five patients and investigating five suspected cases.