State health officials are investigating a puzzling outbreak of mumps in Latino communities in Boston, Chelsea, and Revere, and have advised health care providers to be alert for additional cases. The state Department of Public Health has recorded 12 mumps cases since the end of March. Previously in Massachusetts, mumps has been found chiefly among vaccinated college students and others connected to colleges and universities. But the dozen new cases involve people aged 20 to 41 with no known links to higher education.