Strawberries sold at roadside and farmer’s markets last month in Oregon have been implicated in an outbreak of E. coli O157:H7 infection that has caused one death and sickened as many as 15 others, the Oregon Department of Public Health announced Monday.
The outbreak sent four people to the hospital and two suffered hemolytic uremic syndrome. One, an elderly woman from Washington County, died from kidney failure caused by the disease.
So far, health investigators think deer may be to blame for the E. coli contamination. Deer tracks and deer feces were observed in several strawberry fields at the suspect farm, according to health investigators.
Tracing the berries to that farm was no easy task. Between July 10 and 29, at least 10 and as many as 16 people fell ill in Oregon with E. coli O157:H7 infections. It was not until last week – when genetic fingerprinting revealed that 10 people had been infected with identical strains of E. coli bacteria – that epidemiologists knew they had an outbreak on their hands.
Interviewing case patients with what Oregon health investigators call their “shotgun questionnaire,” an exhaustive checklist that includes everything from spices to sunflower seeds to petting zoos, produced interesting and unusual results.
Nearly all the case patients recalled eating strawberries and said they had shopped at local farmer’s markets or fruit stands in the preceding weeks, according to state epidemiologist Katrina Hedberg.
Further questioning revealed that all the local strawberry vendors had a single supplier in common: Jaquith Strawberry Farm in Newberg.
But, as Hedberg explained to Food Safety News, pinpointing the farm was where things got more complicated, not easier. The farm sells its strawberries to a wide array of secondary vendors, who in turn sell them at local fruit stands. Once they’re there, there’s nothing to differentiate fruit from Farm A from that of Farm B.
“The traceback here is very difficult,” she says. “A lot of these berries are sold at roadside stands, so they’re really not labeled.”
For that reason, health department officials could not give consumers lot numbers or packaging details to look for, but instead have advised people not to eat strawberries purchased from Northwest Oregon farm stands in July. The strawberries were not sold in supermarkets.
The strawberry harvest in Oregon strawberries is now over, and the local berries have a shelf life of only about 2 days, according to Hedberg, so fresh strawberries no longer present a hazard.
However, residents of Northwest Oregon, specifically in Washington, Clatsop and Multnomah counties, are advised not to eat frozen strawberries or uncooked jams purchased from fresh fruits stands because those berries could still be carrying the bacteria.
The berries may also have been sold at “one or two farm stands in Clark County,” Hedberg says, although that possibility has not been confirmed.
The contaminated berries were likely limited to Oregon. “We don’t expect these cases to be any more widely distributed to any other states,” says Hedberg, “just because of the fragile nature of [the strawberries].”
In the meantime, the search for a source of E. coli O157:H7 on the farm continues. Hedberg says the leading hypothesis is that the bacteria originated in deer feces in one of the fields. Investigators are taking samples of soil, feces and plants to test for the outbreak strain of E. coli.
“If we could pinpoint it to a particular field, that would be extremely useful,” she added. Hedberg said the Jaquiths, long-time strawberry growers, are being “very cooperative … they really want to get to the bottom of this, too.”
Hedberg says the outbreak has been a blow to Oregon residents, who enjoy eating regional strawberries in the summer.
“It’s just unfortunate,” she says. “Everyone here in the [Public Health] office loves Oregon strawberries, so we feel really bad, but our job is to protect the health of local Oregonians.”
This is the first E. coli O157:H7 outbreak linked to strawberries, although the bacteria has been associated with many outbreaks involving fresh produce, as well as undercooked meat. In 2006, an outbreak caused by another Shiga toxin-producing strain of E. coli, O26, was linked to strawberries or blueberries in Massachusetts, according to the Foodborne Illness Outbreak Database.