COLDWATER, Mich. (AP) — A health official says cases of whooping cough are spreading among Amish residents in southwestern Michigan.

Val Newton, prevention services director for the Branch-Hillsdale-St. Joseph Community Health Agency, told the agency’s board Thursday that whooping cough, or pertussis, has struck up to 30 members of St. Joseph County’s Amish community.

The Daily Reporter of Coldwater reports that there is concern that the highly contagious bacterial infection could spread to Branch and Hillsdale counties.

Pertussis can be prevented with vaccines and treated with antibiotics. Newton says the first area family affected by whooping cough declined treatment. Doctors in the three counties are being contacted to suggest testing patients — especially young children.

Whooping cough is usually spread by coughing or sneezing. It causes a severe cough that can last for months.