Hundreds of millions of eggs are being recalled because they may be contaminated with the foodborne bacterium salmonella which causes diarrhea, vomiting, and nausea among those unfortunate enough to become infected. It is estimated that as many 1.4 million Americans become infected each year and perhaps as many as 500 die of the disease. So how bad is the current outbreak? The U.S. Centers for Disease Control and Prevention (CDC) has just released data that suggests that the outbreak rose to four times the normal rate—from about 55 cases to about 220 reported cases per week in June.
Number of Salmonella Enteritidis cases matching PFGE pattern JEGX01.0004 reported to PulseNet, United States, 2010
*Date of isolation by week.
In May 2010, CDC identified a nationwide increase in the number of Salmonella Enteritidis isolates with PFGE pattern JEGX01.0004 uploaded to PulseNet, the national subtyping network made up of state and local public health laboratories and federal food regulatory laboratories that performs molecular surveillance of foodborne infections. This increase is evident in the epidemic curve, or epi curve. During May 1 to July 31, 2010, a total of 1,953 illnesses were reported. However, some of these cases may not be related to this outbreak. Based on the previous 5 years of reports to PulseNet, we would expect approximately 700 illnesses during this same period.
To put this outbreak in perspective, it bucks a decade long trend toward lower reported incidence for most foodborne illness according to data from the CDC's FoodNet reporting system:
In comparison with the 1996–1998 period, rates of infection in 2009 were lower for Shigella (55% decrease), Yersinia (53% decrease), STEC O157 (41% decrease), Campylobacter (30% decrease), Listeria (26% decrease), and Salmonella (10% decrease); rates were higher for Vibrio (85% increase).