Source of E.coli spread remains mystery

Federal and state health officials are still investigating the source of E.coli spread that killed three people and sickened almost 200 others nationwide.

Investigators pinpointed cattle feces as a possible source, but they still don't know how the lethal bacteria spread to the fields and tainted so much food, officials said on Saturday.

Experts need to figure out the mechanism of transport to the spinach fields. They said if it's a short distance, wind can transport the bacteria, so can floods and rain. The bacteria can be also transported by people walking from one side to another.

Federal and state investigators announced on Thursday that they have matched E. coli O157:H7 in feces from an unidentified cattle ranch in California to the bacteria found in sick people as well as bagged spinach they ate.

Experts said spinach fields are close to cattle ranches, leading to speculation that cattle manure taints spinach. But experts still cannot find answers to the many mysteries.

Until the mysteries are solved, the safety of the region's leafy greens cannot be assured, experts said.

They raised several questions:

-- how did the pathogen move from cows to crops? Large numbers of wild pigs frequent the ranch and might have fed on manure and excreted it in fields or tracked it there;

-- How did the manure spread to so much spinach? Runoff or spring flooding could have transported feces from the ranch, but the suspect cattle pastures are downhill from spinach fields; and

-- Are there other sources? There have been eight previous outbreaks that have been traced back to other lettuce in California's Salina Valley and spinach fields over the last decade.

Kevin Reilly, deputy director of the state Department of Health Services' prevention services division, said 13 people from his agency and the Federal and Drug Administration were taking samples in four fields Friday, focusing on the cattle ranch and trying to find out "precisely how the contamination could have reached the actual spinach on the fields."

"We're talking about detective work ... We don't have that definitive evidence yet but we have a number of clues," he said.

Food experts have long known that leafy vegetables are susceptible to pathogens, hosting more fecal bacteria than other produce. In laboratories, pathogens live for weeks on leafy greens, thriving even as the vegetables wilt. And in soil, they survive for months.

Source: Xinhua