Thursday, September 15, 2011


This has not been a good few weeks for Americans at high risk for Listeriosis - that potentially life-threatening disease caused by Listeria bacteria, usually in food. Such people include pregnant women (because of risks to the fetus), and older or sicker adults. Death occurs in some 16-20% of serious cases. This makes Listeriosis one of the most deadly foodborne illnesses we know.

Incidence of Listeriosis goes up and down, but generally seems to be on the increase. That is the case in several European countries, England, Wales, and, in the US. In the United States, there is also seasonal variation - worse during summer months.

L. monocytogenes can be present in soil and water, and can crop up in whole raw vegetables (such as the recent incidence in whole cantaloupes from Colorado). It can also turn up in raw dairy foods and meat products. But more frequently, this bacteria is found in processed or lightly-processed foods, such as ready-to-eat washed and cut up produce, deli meats, prepared salads, cheeses, and so on. One example is the recently recalled frozen avaocado pulp, imported from Peru. This bacteria withstands freezing very well.

What happens is that the bacteria usually get in during the preparation process, often from the workers handling the food. Why? Because a high percentage of them are carriers, although they may not be ill. How high a percentage? Estimates vary - probably somewhere between 5% and 30%, which is a very broad range. Unfortunately, the evidence suggests that such numbers are increasing - and so is Listeria contamination in our food.

Of course, the fact that we are eating more and more of those time-saving ready-to eat convenience foods, adds to our increasing risk. Avoid them as much as you can!

To your good health,

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