In less than a year, there have been two country wide salmonella outbreaks in the US. The first outbreak of Salmonella Saintpaul occurred last summer of 2008, and infected as many as 1,442 persons over five months. The origin has still not been confirmed however tomatoes and peppers have been linked to the illnesses. The second and current outbreak of Salmonella Typhimurium began in November 2008 and as of February 18th 2009 infected as many as 654 persons. This outbreak is linked to peanut butter from the Peanut Corporation of America. On January 28th, 2009, the PCA recalled all peanut products from the Blakely, Georgia plant and on February 12th, 2009 they were forced to recall all products from the Plainview, Texas plant. The FDA has an updated list of recalled products.

As a geographer, the question of how salmonella spread spatially throughout the U.S. is an interesting one. During the Salmonella Saintpaul outbreak, I did a blog showing the distribution of Salmonella cases by state over time.

It is likely that the origin of the Salmonella Saintpaul was in Mexico, and one can clearly see the concentration of cases in the Texas/New Mexico area and then spread in a fan like shape outward to surrounding states. Below is a similar series of maps showing the spread of Salmonella Typhimurium from January 9th to January 15th 2009.

The nature of the current outbreak is quite different. Because the contamination was in a food ingredient used in many processed products, the spread of the outbreak is much more random and well… less geographic. See the maps below comparing the two outbreaks. One would have to map out the supply chain of products from the plant in order to explain why California and Ohio have had the most cases meanwhile, the states of origin have had relatively few.

You can see the dataset for Salmonella Saintpaul here and for Salmonella Typhimurium here.

While over five months, the Saintpaul outbreak contributed to more than twice as many cases as did the current outbreak in four months, the current strain seems to be much more dangerous. The peanut butter related outbreak may have already caused nine deaths while the outbreak over the summer was only contributed to two deaths. Luckily, because the source of the current outbreak has been identified and because the distribution of processed products may be easier to trace than fresh produce, contaminated products have been identified. The current outbreak may linger longer however, since it affects packaged products with a long shelf live that may be continued to be eaten by people not aware of the recalled products.

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