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Thursday, June 23, 2011
Q&A with Jason Harris, MD
Jason Harris, MD, assistant professor of pediatrics at Harvard Medical School and a specialist in pediatric infectious disease at MassGeneral Hospital for Children, answers questions about the recent E. coli outbreak in Europe and explains what you can do to protect your family from food-borne illness.
Q: Why is the outbreak in Europe so large and why has it been so hard for health officials to identify the source?
A: Outbreaks of food-borne illness have gotten more complicated and it’s become difficult to identify the source in many cases because of the globalization of the food industry. The classic example of a food-borne illness outbreak is the church picnic where everybody eats the potato salad and gets sick. It’s pretty obvious what the culprit is in that case. But a lot of the outbreaks we’re seeing now originate from either a grower or a processor that distributes food across a wide region. In these cases, you’ve got a very wide geographic area that’s involved and the contaminated food may be a component of many other prepared foods.
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As an example, here in the U.S., there was an outbreak of hepatitis A that was traced to frozen strawberries produced in Mexico. Initially the outbreak was identified by a cluster of cases in one area, but when epidemiologists traced it back to the source, they were able to identify numerous other small outbreaks associated with the same frozen strawberry producers across several states.
Another example is the large outbreak of salmonellosis in the U.S., in 2008, which was associated with contaminated peanut butter processed at a plant in Georgia. This peanut butter was not sold as peanut butter per se, but was sold to food producers and incorporated into numerous other processed foods like peanut-butter cheese crackers, and these were distributed all over the country. This led to cases of salmonellosis in more than 40 states.
Q: Is this a new form of E. coli?
A: E. coli O 104 had been described as a rare cause of hemolytic uremic syndrome (HUS). HUS is a disorder caused when an infection in the digestive system releases toxins into the blood that cause kidney damage. There have only been a few sporadic cases of E. coli O 104:H4, nothing like the current outbreak in Europe. Also, the E. coli O 104:H4 strain has characteristics of multiple pathogens (a pathogen is a microbe that causes disease), and seems to combine the attributes of two different types of disease-causing E. coli. For that reason, it looks like an especially potent pathogen.
Q: Is there any danger in the United States?
A: From this specific outbreak, it doesn’t seem like there’s an immediate risk. There have been a handful of cases in people who’ve either traveled to Germany or had contact with people who were traveling in Germany who have developed the infection, but the outbreak has not really spread to other countries other than in these cases. It appears that the foods that were causing this were only distributed in Germany.
Q: Now that E. coli has changed in Europe should we be looking for a new form in the United States that might be more dangerous?
A: There’s always a concern that stronger strains will evolve. A large percentage of the hemolytic uremic syndrome cases in this country are caused by another E. coli strain, O 157:H7, but even here it seems that the number of cases due to the non-O157 strains is increasing. Although we have not had an epidemic reaching the magnitude of the one in Europe, I think it’s a concern and something to be vigilant about.
Q: Is meat still the main source of E. coli? Some recent outbreaks have been associated with vegetables.
A: Major E. coli outbreaks have been associated with undercooked meats and unpasteurized juice. An increasing proportion now, like the current outbreak in Germany, is associated with fresh fruits and vegetables. As these are not always cooked, washing your produce thoroughly is a very important thing to do.
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