Officials from the Branch-Hillsdale-St. Joseph Community Health Agency continue to investigate incidents of pertussis in St. Joseph County.
About 320 people have been treated with antibiotics in the past month, according to Val Newton, prevention services director. Occurrences began in June, then spread.
Newton said treatment has been confined to the Amish community, with one exception. The Amish family volunteered to set up space at its home for people to receive immunizations
To date, 34 people have received 60 vaccines, Newton said.
The infection, more commonly known as whooping cough, is most serious in babies. It typically starts with cold-like symptoms, mild cough or fever.