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2016 Shigellosis Outbreak - Genesee and Saginaw Counties

This page contains information about the 2016 Shigellosis Outbreak in Genesee and Saginaw Counties, Michigan.

 Outbreak At-A-Glance

Since March 1, 2016
Total Cases: 180
Saginaw County: 51
Genesee County: 129


 Information Highlights

Outbreak of Shigella sonnei in Genesee and Saginaw counties

  • Genesee and Saginaw counties are experiencing an outbreak of diarrheal disease caused by a bacteria called Shigella.
  • At least 180 cases of Shigella infection have been reported throughout the two counties between March 1, 2016, and November 14, 2016. That is more cases than we’ve seen during the same period in previous years.
  • MDHHS is working with the Centers for Disease Control and Prevention (CDC) and the county health departments to learn more about how people may have gotten sick.
  • As a part of this investigation, public health officials are:
    • Contacting people in Saginaw and Genesee counties who got sick from Shigella to learn more about their illness.
    • Doing additional laboratory testing of samples collected from people who got sick from Shigella across Michigan.
    • Mapping where cases have occurred to see if there is a link between water quality issues and the people who got sick. Examples of possible water quality issues include water main breaks and areas that have low chlorine levels.
  • Although no cause has been identified for this outbreak, the information collected so far suggests the Shigella bacteria is spreading from person-to-person.
  • Update Letter to the Community - 12/15/2016
  • Interim Findings from the Shigellosis Outbreak Investigation (Presentation) - 12/15/2016
  • Update Letter to the Community - 11/17/2016
  • Update Letter to Healthcare Providers - 11/17/2016


 Outbreak Summary


State, local and federal public health officials, partner organizations, and community residents are collaborating to learn more about how people from Saginaw and Genesee counties may have gotten sick with Shigella bacteria.

Shigella outbreaks are not unusual. They occur across the United States, with around 25,000 infections reported each year and an average of 300 to 400 infections reported in Michigan each year.

MDHHS tracks cases of shigellosis illnesses based on reports submitted by healthcare providers. These reports showed increases in cases in Saginaw and Genesee counties beginning in June, and laboratory testing showed that the cases in both counties were caused by the same types of Shigella bacteria. MDHHS requested CDC assistance in investigating what might be causing people to get sick. 

One-hundred and eighty cases of Shigella infection were reported from Saginaw and Genesee counties between March 1, 2016, and November 14, 2016. The number of ill people identified in each county were as follows: Saginaw (51) and Genesee (129).

Sick people ranged in age from less than 1 to 86 years. Many of the people who got sick are children, and 60% of the people who got sick are female.

Investigation of the Outbreak

As part of this investigation, health officials are contacting the people who got sick to learn more about their illness and ask about different things that could contribute to the spread of Shigella infection. Health officials are mapping where cases have occurred to see if there is a link between water quality issues, like water main breaks and low chlorine levels, and the people who got sick. MDHHS is also working with CDC to look into Shigella infections that occurred in other parts of Michigan to see if they are connected to the outbreak in Saginaw and Genesee counties.

Current data suggest the shigellosis outbreak is being spread person-to-person and did not begin from a contaminated point source, like a drinking water system. Shigella infection outbreaks related to drinking water systems are rare, because Shigella bacteria are easily killed by chlorine. Previous Shigella-related drinking water outbreaks in the United States typically involved contamination of a private well by sewage. If this initial investigation shows any indication that water is a potential source of the outbreak, public health authorities will follow-up with additional, detailed investigations. Regular updates on the progress of the investigation will be provided at community meetings and with the healthcare community.

Graph of Shigella Cases in Saginaw & Genesee County


 General Information About Shigellosis

What is Shigella?

Shigella is a germ that causes a disease called shigellosis. People sick with shigellosis may have diarrhea and other symptoms, like stomach cramps and fever. In most cases, sick people will get better without medicine within 5 to 7 days. Some people, like people who are already sick with other diseases, may take longer to get better or may need antibiotics.

How Do People Get Sick from Shigella Bacteria?

It only takes a very small amount of Shigella germs – an amount so small it can’t be seen by the naked eye – to make someone sick. People usually get sick from Shigella 1–3 days after putting something in their mouth or swallowing something that has come into contact with the stool (poop) of someone else who is sick from Shigella bacteria. For example, people could get sick by:

  • Changing diapers of children who are infected with the germ.

  • Touching people who are sick that might have the germ on their hands or bodies.

  • Eating food that was prepared by someone who is sick with the germ.

How Can I Avoid Getting Sick from Shigella Bacteria?

Shigella germs can spread very easily from person to person, so the single best thing you can do to keep from getting sick is to wash your hands with soap and water— especially after using the bathroom, after changing a child’s diapers, and before preparing food.

If soap and water are not available, you can use an alcohol-based hand sanitizer with at least 60% alcohol. Hand sanitizer with at least 60% alcohol is effective in killing Shigella germs. But use soap and water as soon as possible afterwards because hand sanitizer does not kill all types of germs and may not be as effective if hands are visibly greasy or dirty. Other products like cleansing wipes (including baby wipes) do not completely remove germs and are not recommended for cleaning hands.

What Should I Do If I Think I am Sick with Shigella?

If you or one of your family members have the symptoms of shigellosis, such as diarrhea, fever, and a stomachache, visit your doctor and ask about testing for Shigella. Your doctor can order a test that will show whether you or one of your family members are sick from Shigella. It is also important to drink fluids to stay hydrated and wash hands often with soap and water to keep from spreading the sickness to others.


More Information/Resources

Below are links to more information and resources on Shigella and shigellosis.