Foodborne illness outbreaks are often a mystery. Oftentimes, it will be easy to link victims of foodborne illness to each other based on what bacteria made them ill. However, finding the source of the contamination can be difficult. In the wake of the Salmonella outbreak linked to Persian cucumbers announced by the Centers for Disease Control and Prevention (CDC) in December, another foodborne illness outbreak has been made public knowledge after the outbreak itself took place.

In January 2016, though, the PulseNet system maintained by health officials identified a series of connected cases of E. coli poisoning. This cluster of 10 cases of illness had near identical pulsed-field gel electrophoresis (PFGE) results. Upon further investigation, the original 10 illnesses were expanded to 13 cases of E. coli poisoning. These cases of illness began between December 6, 2015 and continued until February 9, 2016. The 13 cases of illness were found to be spread out over 9 states, including Wisconsin with 1 case, South Dakota with 1 case, New Jersey with 1 case, Nebraska with 1 case, North Carolina with 1 case, Minnesota with 5 cases, Kansas with 1 case, Illinois with 1 case, and Iowa with 1 case. More detailed information was able to be obtained from 12 of the cases of illness. From this information, health investigators were able to find that 8 people were hospitalized for their illness. Two people reported developing a serious syndrome caused by E. coli poisoning, hemolytic uremic syndrome (HUS). Nine people reported eating at a national restaurant chain referred to as “Restaurant A” by the CDC report. Out of these 9 people, 8 of them reported eating a specific dessert pizza. The last person reported eating bread sticks, and health investigators later discovered that both products were made with the same dough, which had been provided by Restaurant A. Samples were then taken from 5 different restaurant locations visited by ill people. The Minnesota Department of Agriculture found E. coli bacteria in 7 of the 17 samples that they took. The FDA then took 6 samples from dough found at the manufacturer’s facility and found E. coli in all 6 samples. The source was finally discovered.

The process of investigating an outbreak usually occurs after there is a spike in illnesses. Health officials have studied for years the average rate that specific pathogens cause illness, and are able to track when these background infections suddenly change. When a random spike in illnesses is detected, health officials can then investigate the outbreak, usually by taking samples and by conducting interviews. There is sometimes a correlation between interview answers, which can help investigators locate a source. Although interviews can help locate potential sources, the best way for health officials to learn more about an outbreak is through the testing of samples. When medical providers retrieve samples from ill people or from the environment, the samples undergo testing to learn more about them. This type of testing reveals the bacteria’s DNA fingerprint. This fingerprint, a solution of the process of PFGE, is unique to the bacteria and strain involved in the outbreak. However, in some cases, the process of PFGE is not enough to get a clear picture about the specific pathogen responsible for the illness. This usually occurs with pathogens that evolve quickly, or have a tendency to look similar to other strains or pathogens. The outbreak reported by the CDC represents an example of this. Because the specific strain of E. coli responsible for this outbreak is very common, causing about 40-50 cases to be reported to PulseNet each year, health officials chose to run more in-depth testing on the collected samples using the method of Multiple Locus Variable-Number Tandem Repeat Analysis (MLVA). MLVA is often used alongside PFGE tests to help scientists get a clearer picture of the pathogen responsible for the infection. This is mainly used for pathogens that evolve quickly, or have a tendency to look similar to other strains or pathogens. The process itself involves the passage of DNA strings through a gel environment. A set of lasers is typically run through the gel at the same time, in order to provide a detailed graph of the DNA strands called an electropherogram. The DNA fingerprint is then uploaded to the PulseNet system. The PulseNet system is a database of DNA fingerprints maintained by the CDC. If a saved sample matches another sample, there may be a connection between the two. When multiple samples match through the PulseNet system, it is another clue to investigators about the origin and size of the outbreak.

E. coli infections are one of the most common forms of foodborne illness. The CDC estimates that around 265,000 E. coli infections occur annually in the United States. When someone is exposed to pathogenic E. coli bacteria via contaminated food or water, they can expect to see symptoms within an average of 3 or 4 days. Most of the time, the bacteria produces symptoms as early as one day or as late as ten days after the initial exposure. Symptoms of E. coli poisoning can vary, but most of the time they include vomiting, fever, stomach cramps, and diarrhea. Doctors may test to confirm the presence of E. coli, but in most cases the best treatment for E. coli is rest and hydration. In a majority of instances, an E. coli infection will subside on its own within a week. However, some cases of E. coli infection can be life threatening. While E. coli infections can affect people from any age group and background, young children, the elderly, and those with suppressed immune systems are at an increased risk of developing a serious E. coli infection or even hemolytic uremic syndrome. In about 5 to 10 percent of E. coli poisoning cases, a complication called hemolytic uremic syndrome (HUS) arises. HUS is a complication that damages red blood cells. These damaged blood cells eventually travel to the kidneys, where they are filtered out of the bloodstream. Filtering these HUS-affected blood cells and removing them from the bloodstream can cause damage to the kidneys, and could even lead to kidney failure. HUS can cause other symptoms, including decreased frequency of urination, loss of color in the eyes and cheeks, and fatigue. Health officials with the Kansas Department of Agriculture have recommended that anyone who experienced diarrhea within ten days of attending the Louisburg Mill Ciderfest should contact them. If you or a loved one begins to show the symptoms of E. coli poisoning or HUS, contact a medical professional.

Sources:

https://www.cdc.gov/pulsenet/pathogens/mlva.html

https://www.cdc.gov/mmwr/volumes/66/wr/mm6603a6.htm?s_cid=mm6603a6_