Island physicians and residents are being urged to be especially wary of possible measles infections and to keep up with the recommended immunizations. The state Department of Health reported yesterday that nine cases have been identified in Hawai`i so far this year, compared to zero cases at this time in 2002. "We're concerned about these locally-acquired cases because measles is such a highly contagious disease," said state epidemiologist Dr. Paul Effler. "The best defense against measles is vaccination."