A rare strain of E. coli O157:H7 never before seen in the national PulseNet database is responsible for the 25 illnesses preliminarily linked to cheese sold or offered in taste samples at Costco, according to the Centers for Disease Control and Prevention.

PulseNet is the network of state and local public health laboratories and federal food regulatory laboratories that uses molecular surveillance to track foodborne infections.  It helps epidemiologists connect cases and recognize outbreaks by comparing DNA fingerprints of the bacteria that cause illness.

In its first investigative summary of the outbreak, the CDC says preliminary laboratory testing was conducted on an opened package of Bravo Farms Dutch Style Raw Milk Gouda Cheese, taken from an outbreak patient’s home.  The patient had purchased the cheese at a Costco Warehouse.  The tests indicated the presence of E. coli O157:H7 matching the PulseNet-identified outbreak strain.  Additional lab testing is being done to confirm the result.

The Bravo Farms Dutch Style Gouda Cheese was featured in a “cheese road show” promotion at Costco between Oct. 5 and Nov. 1, the investigative summary said.

According to the Bravo Farms website, its gouda-style cheese is made from raw whole milk aged for 2 months.  Costco has recalled the product.


The CDC said the 25 people infected with the outbreak strain of E. coli   range in age from 2 to 81 years.  The median age is 14 years.  Eleven of the people live in Arizona, eight in Colorado, three in New Mexico, two in Nevada and one in California.

The California patient was a 6-year-old girl from San Diego County, according to the San Diego County Health and Human Services Agency.

“The girl is doing well now and did not need to be hospitalized,” said Dr. Dean Sidelinger, the county deputy public health officer, in a news release.

New Mexico’s cases involved a 41-year-old man and 7-year-old girl from Bernalillo County and a 4-year-old boy from Valencia County.  All three are recovering, according to the New Mexico Department of Health. No one in New Mexico was hospitalized, the department said in a news release.

Of the eight cases in Colorado, four people were from Douglas County, three from Arapahoe and one from Boulder, the Colorado Department of Public Health and Environment reported in a statement.

The Tri-County Health Department in Colorado, which covers Adams, Arapahoe and Douglas counties, has had the highest number of cases in the state.  It says it played a key role in linking the illnesses with the cheese served and sold at Costco, according to the agency’s executive director, Dr. Richard Vogt.

In the first report on the outbreak, health authorities said nine people had been hospitalized and there was one possible case of hemolytic uremic syndrome (HUS).

The onset of the illnesses ranged from Oct. 16 through Oct. 24, 2010.  But illnesses that occurred after Oct. 18 might not yet be reported, the CDC said, because it can typically take 2 to 3 weeks from the time a person becomes ill to when the illness is reported.

The CDC said it is working with public health officials in the affected states as well as the Food and Drug Administration (FDA), and the Food Safety and Inspection Service (FSIS) to investigate the outbreak.

That investigation includes:

•Conducting surveillance for additional illnesses that could be related to the outbreak.

•Conducting epidemiologic studies that include collecting detailed information from ill persons (cases) and from healthy persons (controls) about foods recently eaten and other exposures.

•Gathering and testing food products that are suspected as possible sources of infection to see if they are contaminated with bacteria.

•Following epidemiologic leads gathered from interviews with patients, food purchase information, or from patterns of processing, production and/or distribution of suspected products.

•Investigating where in the distribution chain the point of contamination could have occurred.

Graphic of outbreak incidence from the Centers for Disease Control and Prevention.