Four of 10 areas sampled at the Northwest Fairgrounds in Lynden, WA, match the outbreak strain of E. coli O157:H7 that has now sickened 25 people in Whatcom County, WA.

The Lynden fairgrounds was the site of the April 21-23 Milk Makers Fest attended by more than 1,300 children from locals schools. Among the features presented there was a farm animal petting zoo. All of those sickened in this outbreak attended the dairy event, helped set it up, or are relatives or close contacts of people who were there. environmental test results were reported Friday afternoon in the latest update from the Washington State Department of Health (DOH).

The on-site investigative team, including health officials from the U.S. Centers for Disease Control and Prevention (CDC), DOH and Whatcom County, has not announced any specific source(s) of the infections but appears to be narrowing down the focus.

DOH also announced Friday that the latest confirmed case count is now at 25 people, with nine of those considered secondary cases, meaning that those particular individuals didn’t attend the fairgrounds event but had close contact with someone who did. There are also several other people whose illnesses are under investigation as possibly being connected to the outbreak, according to the DOH update.

No one has died in the outbreak, although 10 people have been hospitalized and four of them developed hemolytic uremic syndrome (HUS), a kidney disease associated with E. coli infections.

DOH is not revealing where the positive test samples have been taken out of concern that the information could influence people being interviewed in connection with the outbreak.

Donn Moyer, DOH media relations manager, told Food Safety News that the investigative team had done some recollecting of environmental samples and that his department does its own DNA fingerprinting at its certified lab.

He said the four-person CDC team is expected to be on the scene a while longer. DOH and county officials had asked CDC to help with data collection, case definition, and other outbreak investigation work, and the federal officials have been in Washington state working on the outbreak since May 11.

DOH advises anyone who attended the Milk Makers Fest, or has close contact with someone ill who did, and has signs or symptoms of E. coli infection to see a doctor. People usually get sick from E. coli 2-8 days (average of 3-4 days) after exposure to the bacteria. Only people who have symptoms should see a doctor in relation to this outbreak.

Symptoms of E. coli infection include diarrhea (often bloody) and abdominal cramps, and most people recover within a week. Some illnesses last longer and can be more severe.

DOH provided the following precautions for those infected with E. coli or those with a family member infected with E. coli:

  • 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 from CDC on E. coli O157:H7 is available here.