Thirteen people from Arizona, California, and Nevada who ate beef tacos from a national fast-food restaurant chain in 1999 became infected with Escherichia coli, according to a study in the June 15 issue of Clinical Infectious Diseases, now available online.
Epidemiologists found that evidence pointed to the ground beef as the problem taco ingredient. A strain of E coli, which can cause people to suffer bloody diarrhea and renal problems, occurs in the manure of some healt hy cattle; any meat that comes into contact with that manure in slaughterhouses can become contaminated. In this study, a slaughterhouse in Idaho was the source of beef that was distributed to several Mexican-style restaurants in California and Nevada. The single Arizona restaurant affected by the outbreak may have been supplied with meat transferred from Nevada.
E coli can be killed by cooking ground meat to at least 160º F. When inspectors examined the restaurants' self-monitored temperature data after being notified of the potential exposure to E coli, the documents showed a flaw in only one of the restaurants' meat handling. However, that doesn't necessarily mean the other restaurants did everything correctly.
"The reality is that by time the illnesses are diagnosed, the reports are submitted to the health department, and the epidemiological study is completed, it could be weeks since the actual exposure to the contaminated food," said Dr. Michele Jay of the California Department of Health Services and lead author of the study. "Additionally, investigators are depending on written records from the food facilities that may be incomplete."
There are, however, potential solutions on the horizon to help combat E coli outbreaks. The U.S. Department of Agriculture's Animal and Plant Health Inspection Service plans to phase in a tracking system over the next five years that would enable the tracing of meat products back to their sources. Such a system would also allow epidemiologists to compare distribution of human illness cases with distribution of the food in question.
In the meantime, doctors need to watch patients for symptoms of E coli and other foodborne illness, which may include bloody or prolonged diarrhea, weight loss, fever, and vomiting, said Dr. Jay. Very old, very young, and immunocompromised patients are more susceptible to E coli, and physicians should be sure to ask about activities that could have put patients at risk for the infection, such as eating raw or undercooked food, drinking unpasteurized milk, coming into contact with farm animals, or visiting a farm.
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