"Outbreak" means the occurrence of more cases of a disease than would normally be expected in a specific place (e.g., linked by institution, affiliation, exposure, small geographic area), group of people (e.g., long-term care residents, students, and over a specific time period (e.g., within 2 weeks).

Example 1: One classroom in a school having 14 out of 20 students out sick with influenza (flu) during the second week of December. We expect to see some flu in a school during flu season, but having one classroom with more cases than expected would potentially indicate an outbreak.

Example 2: 15 cases of Shiga toxin-producing E. coli that occurred among individuals who all stopped at the same restaurant to eat dinner in the same week. We are seeing cases linked to a common source, a common time period, and a common space.

• Any person, including but not limited to a physician, dentist, nurse, medical examiner, other healthcare practitioner, administrator of a health care facility or laboratory, public or private school administrator, day care facility or youth camp personnel, or laboratory professional who knows or has reason to suspect that a case or outbreak exists of a reportable disease or condition defined in ARM 37.114.203.
• Any setting in which a group of unrelated persons reside, meet, or gather either for a limited or extended period of time in close physical proximity. This includes correctional facilities, day care facilities and other early childhood education facilities, detention centers, group homes, health care facilities as defined in 50-5-101, MCA, schools, and youth camps.

• Any condition listed in ARM 37.14.203.
  • Click here for a printable list of reportable conditions in Montana.
• An outbreak of any communicable disease listed in the "Control of Communicable Diseases Manual" that occurs in an institutional or congregate setting. This includes outbreaks of illnesses such as hand, food, and mouth disease, norovirus, and RSV, as well as outbreaks with an unknown cause (e.g., multiple people with a respiratory infection or stomach illness).
  • Definition of "institutional or congregate setting": means a setting in which a group of unrelated persons reside, meet, or gather either for a limited or extended period of time in close physical proximity. The term includes (but is not limited to) correctional facilities, day care facilities and other early childhood education facilities, detention centers, group homes, health care facilities as defined in 50-5-101, MCA, schools, and youth camps.

Collecting information below about outbreaks allows public health to mitigate outbreaks in a timely manner.

• Important Dates
  • Date that the first person associated with the outbreak became ill
  • Date that the outbreak was first identified
  • Date that the last person associated with the outbreak became ill
• Facility Details
  • Facility name and location
  • Facility type (e.g., hospital, day care, food establishment)
  • Number of ill residents, employees, attendees, etc.
  • Number of exposed residents, employees, attendees, etc.
• Cause of Illness (e.g., COVID-19, norovirus, HFMD)
• Contact Tracing
  • Vaccination history
  • Identifying individuals at risk for severe illness
• Exposure History (e.g., foods eaten recently, places traveled, water exposures, animal exposures)
• Any Hospitalizations or Deaths Associated with the Outbreak

• If you suspect that your facility is experiencing an outbreak of a communicable disease or condition, contact your local or tribal health department immediately for resources, guidance, and next steps.
• If your local or tribal health department are not available, contact the Communicable Disease Epidemiology Section at (406) 444-0273.