E. coli outbreak only the latest to be traced to produce from California

WASHINGTON — Federal health officials told California farmers to improve produce safety in a pointed warning letter last November, nearly a year before the multistate E. coli outbreak linked to spinach.

In fact, the current food-poisoning episode is the 20th since 1995 linked to spinach or lettuce, the Food and Drug Administration said.

Though state and federal officials have traced the current outbreak to a California company's fresh spinach, they haven't pinpointed the source of the bacteria that have killed one person and sickened at least 113 others.

The regulatory agency does not consider the contamination deliberate.

"There is always a question in the back of our mind whether it may have been a deliberate attack on the food supply. Currently, there is nothing in the epidemiology to consider this deliberate," said Dr. David Acheson of the FDA's Center for Food Safety and Applied Nutrition.

That leaves a broad range of other possible sources, including contaminated irrigation water that's been a problem in California's Salinas Valley. The area on California's central coast produces much of the U.S. spinach crop.

There have been 19 other outbreaks of Escherichia coli O157:H7 linked to lettuce and spinach since 1995, according to the FDA. At least eight were traced to the Salinas Valley. The outbreaks involved more than 400 cases of sickness and two deaths.

In 2004 and again in 2005, the FDA's top food-safety official warned California farmers they needed to do more to increase the safety of their fresh leafy greens.

"In light of continuing outbreaks, it is clear that more needs to be done," the FDA's Robert Brackett wrote in a Nov. 4, 2005, letter.

Suggested actions included discarding produce that comes into contact with floodwaters. Rivers and creeks in the Salinas watershed are known to be periodically contaminated with E. coli, Brackett said.

Yet whatever precautionary measures are in place, industry watchers say you can only do so much to control nature.

"You can have a field out in the middle of nowhere grown with filtered water and filtered soil and be completely clean, and have a flock of birds fly over, and birds do what birds do, and the field then becomes contaminated," said Rochell Dornatt, spokeswoman for Rep. Sam Farr, D-Calif., whose district is home to the area dubbed the "salad bowl of the world."

On its way to supermarket shelves, bagged spinach passes from field to packing plant to store, with several opportunities along the journey for it to become contaminated with deadly E. coli bacteria.

This complex chain is making it hard to identify the precise source of the outbreak. The strain of E. coli involved in the current outbreak is the same one that caused high-profile outbreaks associated with Jack-in-the-Box hamburgers that killed four children in Washington state in 1993 and one child who drank Odwalla apple juice in 1996.

The bacteria can live in the intestines of humans and other animals and make a toxin that can cause diarrhea, anemia and, in 2 percent to 7 percent of cases, kidney failure.

Centers for Disease Control and Prevention officials estimate the bacteria cause 73,000 infections and 61 deaths a year.

Produce can also become contaminated by animal wastes or unsanitary water, and outbreaks have been caused by sprouts, lettuce and unpasteurized fruit juice or cider.

Raw milk and unpasteurized cheese can also spread the bacteria. Outbreaks have been linked to petting zoos where children touched farm animals that carried the bacteria.

Produce need only be contaminated with a small quantity of E. coli for a person to fall ill.

Various produce growers' associations worked with the FDA to publish new guidelines for the safe handling of spinach and other leafy greens in April after the agency reiterated its concerns.

A food-safety analyst said the Salinas Valley was developing a reputation for food-safety problems connected to leafy greens.

"Even the biggest companies have become vulnerable," said Trevor Suslow, a microbial-food-safety researcher at the University of California, Davis.

Though health and agricultural officials have spent years trying to trace the precise source of contamination — whether it be tainted water or infected animals or workers — it remains a mystery.

Trace-backs, as they are called, are complicated by the fact that it can be weeks before an infected person is properly diagnosed and even longer before public-health officials determine there is an outbreak. By the time investigators find the original farm, the field is likely plowed under for a new crop.

One hypothesis: Birds and other wildlife might be feeding on cow manure and leaving their droppings in streams that flood nearby fields. One bird's droppings also might contaminate a single head of lettuce, chopped into multiple bags, growers and officials said.

Other potential risk factors include contaminated workers, tainted dust from a nearby cattle field, and compost with manure in it.

"The best guess we can come up with [is] there are a group of circumstances that come together that allow it," said Brackett, director of the FDA's Center for Food Safety and Nutrition.

In a 2005 state report, officials said E. coli had been found in the sediment of a creek bordering a flood-prone field that had been implicated in three separate outbreaks. But the E. coli found in the creek did not match any of the outbreak strains.

In January, California public-health officer Mark Horton wrote a letter to the Western Growers Association saying he had ordered his staff to consider reassessing manure-composting rules, as well as regulations on septic-tank systems that may leak into canals bordering fields.

In addition, they are mulling whether growers should be advised not to grow ready-to-eat crops in fields prone to flooding and assessing the enforcement of rules regarding workers' access to portable toilets and hand-washing facilities.