A Final Investigation Summary released Wednesday by the Whatcom County Health Department in Bellingham, WA, indicates that the source of the recent Shiga toxin-producing E. coli O157:H7 outbreak, which sickened 25 people and hospitalized 10 of them, was probably the Dairy Barn at the Northwest Washington Fairgrounds in Lynden, WA.

http://www.dreamstime.com/stock-photography-dairy-cows-feeding-stable-eating-image52152472All of those who became ill either attended the Milk Makers Fest held April 21-23 at the fairgrounds, helped to set up and/or during the event, or were close contacts of people associated with the event. However, the summary notes that the E. coli contamination “most likely occurred” before the Milk Makers Fest.

Most of those sickened were children, including older ones who helped with the dairy festival. More than 1,000 children from elementary schools in the area attended the Milk Makers Fest.

(The investigation summary also includes information on the final case counts, epidemiologic investigation findings, recommendations for event organizers, and recommendations for the public, which is provided below.)

The investigative team, including county health officials and experts from the Washington State Department of Health and the Centers for Disease Control and Prevention, took multiple environmental samples from the fairgrounds on two different days (April 30 and May 13) and had them tested, the summary states.

“The samples indicated that several areas of the north end of the Dairy Barn at the Northwest Washington Fairgrounds were contaminated with the same strain of E. coli that made people ill. Negative results do not rule out contamination in other parts of the barn.

“The outbreak strain of E. coli O157:H7 was identified in the following areas of the Dairy Barn:

  • Manure bunker
  • Hay maze area
  • Bleachers by east wall
  • Bleachers by west wall

Contamination of the environment most likely occurred before the Milk Makers Fest. Any environment where animals have been kept, such as barns, should be considered contaminated. E.coli 0157 can survive in the environment up to 42 weeks (Varma, 2003 JAMA).”

In a statement posted Wednesday, the Whatcom County Dairy Women, which sponsored the Milk Makers Fest, said the group’s concern has always been with those who became ill and their families.

“Our hearts are broken because of their illnesses and learning about the source does not change our concern or prayers for their complete recovery,” the group stated. “We want to express our deep appreciation to those who worked so hard to identify the source. We were committed from the very beginning to fully support their investigation. Only by identifying a cause can we and all others involved in the important task of agriculture education learn from this and improve the already careful prevention measures.”

The fair manager also released a statement on Wednesday noting that officials there would be doing whatever they could to make events held at the fairgrounds safer for participants.

“The reality is that any time groups host events in proximity to livestock, there is always a heightened chance of coming in contact with bacteria, including E. coli,” Jim Baron told the Bellingham Herald. “What we do know is that the most effective way to prevent contamination is through common-sense steps, including appropriate hand-washing and sanitization.”

In addition to thanking the Whatcom County Dairy Women, the investigative team members said they appreciated the time and support of many people in the community who made the work possible, including the Whatcom County schools, teachers, parents, students, the fair, and clinical and lab providers.

Final case counts

According to the county’s investigation summary, disease investigators calculated case counts based only on lab-confirmed infection with E. coli 0157:H7 or physician-diagnosed hemolytic uremic syndrome (HUS), a type of kidney failure.

  • 25 people were confirmed cases. Nine of these were considered secondary cases (the ill person didn’t attend the Milk Makers Fest but had close contact with someone who did attend).
  • No one died.
  • 10 people were hospitalized.
  • Six people developed HUS.

Epidemiologic investigation findings

As part of the investigation, officials interviewed many of the confirmed cases to find out what they did during the event before they were sickened. Officials also interviewed “controls,” meaning people who attended the Milk Makers Fest but did not get ill to find out what they might have done differently.

The results of analyzing the data collected during the interviews are not final, but a few preliminary findings stand out:

  • Event attendees who reported washing or sanitizing their hands before eating lunch were less likely to become ill.
  • Children who reported always biting their nails were more likely to become ill.
  • Leaving animal areas without washing hands might have contributed to an increased risk of transmission.
  • Eating in animal areas might have contributed to an increased risk of transmission.

Recommendations for event organizers

  • Evaluate and update plans for cleaning and disinfection before, during, and after events, particularly surfaces with high levels of hand contact (such as seats, door or fence handles, and hand railings).
  • Evaluate and update measures to restrict access to areas more likely to be contaminated with animal manure.
  • This is especially important for people at higher risk for severe illness. These people include young children, pregnant women, adults older than 65, and people with weakened immune systems.
  • Ensure access to hand-washing facilities with soap, running water, and disposable towels.
  • Display signs and use other reminders to attendees to wash hands when leaving animal areas.
  • Store, prepare, or serve food and beverages only in non-animal areas.

Recommendations for the public

  • Consider any environment where animals have been kept, such as barns, to be contaminated with bacteria or viruses that can make people ill.
  • Hands should always be washed immediately when exiting animal areas, after removing dirty clothing or shoes, and before eating or drinking.
  • Hand-washing with soap, running water, and disposable towels is the most effective method.
  • Adults should always supervise young children while they wash their hands.
  • Food and beverages should be consumed in non-animal areas and only after washing hands first.
  • Be aware that objects such as clothing, shoes, and stroller wheels can become soiled and serve as a source of germs after leaving an animal area.
  • Nine secondary cases were reported during this outbreak. It’s important for people infected with E. coli or those with a family member infected with E. coli to follow these precautions to prevent secondary infection:
  • Wash your hands thoroughly with soap and water immediately after using the restroom or changing a child’s diaper.
  • Wash your hands before and after preparing food for yourself and others.
  • Stay home from school or work while diarrhea persists. Most people can return to work or school when they no longer have diarrhea. Special precautions are needed for food handlers, health care workers, and child care providers and attendees. Check with your employer before returning to work, and check with your child’s child care center before resuming child care.

More information on E. coli is available from CDC here.