Monday, December 22, 2008

Chile's Listeria Outbreak(s)

December 22, 2008

Chile, with a population of approximately 16.5 million, has recorded 138 lab-confirmed cases of listeriosis so far this year, including 5 deaths.

Fifty-six of the victims were infected with a single outbreak strain of Listeria monocytogenes. That same strain was recovered from samples of Brie Lescure cheese obtained from the refrigerators of two patients.

Chilean government investigators visited the manufacturing facility and reported on December 1st having recovered the outbreak strain from 24 cheese samples. The government immediately prohibited the distribution and sale of all dairy products made at the facility, including all varieties of Chevrita, Las Pircas and Lescure brands of Brie and Camembert cheeses.

Investigations are continuing into the origin of the contamination. Milk used in the production of the cheeses apparently has been ruled out as the source of the Listeria monocytogenes. Suspicion is falling on environmental contamination in the production facility.

The demographics of this outbreak are somewhat different from the recent major outbreak in Canada. The Canadian list of victims was skewed toward the elderly – much of the meat that was the source of the pathogen was distributed to nursing homes and seniors residents. The hardest-hit demographic group – 43% of the victims – in Chile consists of pregnant women. Not surprisingly, there are also a number of newborns and young infants who have been infected – 15% of the outbreak victims.

While the source of this present outbreak seems to have been identified, officials are still puzzling over the unusually large number of confirmed cases of listeriosis reported so far this year – more than five times as many as in either 2006 or 2007. 

The attorney for Chevrita, the manufacturer of the contaminated cheese, was quick to point out that the additional cases are, in his opinion, a clear indication that the problem of Listeria monocytogenes contamination is industry-wide and not specific to his client's production facility. 

Now that the implicated cheese is off the market, the number of new outbreak-related cases should start to diminish. But the long incubation period associated with Listeria monocytogenes means that it will be a couple of months before the Chilean Ministry of Health will be able to close the books on this outbreak.

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