By: James Peacock

Health officials from Seattle & King County Public Health have announced that they are now investigating an outbreak of foodborne illnesses caused by Salmonella bacteria. There have been six total cases of illness associated with this outbreak. The cases of illness were reported to Public Health between July 17 and July 24. The median age of people sickened in the outbreak is 21 years. No one has needed to be hospitalized. Out of the six people sickened, three cases are female and three are male. Health investigators are still searching for a source and will continue to update the public through the use of press releases as more information is discovered.

The process of investigating an outbreak usually involves the taking of samples and the conducting of interviews. There is sometimes a correlation between interview answers, which can help investigators find food or drink items common amongst affected individuals. These commonalities can aid in determining a source. Interviews can help locate potential sources, one of the best ways for health officials to confirm information 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 is the bacteria’s DNA fingerprint. This fingerprint, a solution of the process of pulsed field gel electrophoresis (PFGE), is unique to the bacteria and strain involved in the outbreak. Health investigators will also sometimes run a test called whole genome sequencing (WGS). This test will record the entire DNA sequence of a pathogen and will provide a more detailed report on the pathogen than a PFGE. By looking at clues like these, investigators can figure out what caused an outbreak and just how widespread the outbreak is. In the case of the current Salmonella outbreak in Seattle, tests done on the genetic makeup of the Salmonella revealed on July 26 and 27 that the six cases of illness were genetically related. These results point towards the cases of illness having a common source. Another factor that led to officials declaring an outbreak has to do with the number of cases of Salmonella Stanley that are reported each year. In the Seattle area, they only average between two and six cases of Salmonella Stanley poisoning each year.

The strain implicated in this Salmonellosis outbreak, serotype Stanley, is fairly rarely seen. There has only been one major outbreak caused by Salmonella Stanley in recent years. In 2013 and 2014, there was a Salmonella Stanley outbreak linked to raw cashew cheese that was investigated by the CDC. That outbreak sickened 17 people in three different states. California bore the brunt of the outbreak, reporting 15 of the 17 cases. Wyoming and Nevada both reported one case each. Three people were hospitalized as a result of the outbreak. Salmonella Stanley has also been linked to outbreaks that have impacted reptile communities. According to the CDC’s Salmonella Atlas, the majority of Salmonella Stanley infections occur as a result of contamination of poultry, pork, or reptiles.


Salmonella infections, commonly referred to as Salmonellosis, make up one of the most common forms of foodborne illness in the United States. The CDC estimates that up to 1.2 million cases of Salmonella poisoning occur each year. This estimate includes the fact that many Salmonella cases go unreported and undiagnosed. The tracking of Salmonellosis first took place in 1962, but scientists have been aware of the bacterium for at least the last 125 years. The work of Dr. Salmon and his assistant, Theobald Smith, allowed for the isolation of Salmonella bacteria just 30 years after the acceptance of germ theory. Since that time, the bacteria that make up the Salmonella enterica species have been found to have a variety of strains, or serotypes. These serotypes are based on the various antigens found on the surface and flagella of the bacteria. At the first usage of this method of categorization, 44 different serotypes had been identified. Today there are more than 2000 known serotypes of Salmonella bacteria, but most of them are uncommon sources of foodborne illnesses.  Salmonella infections are usually caused by Salmonella serotypes Enteritidis, Typhimurium, Newport, javiana, Heidelberg, I 4,[5], 12:i:-, Muenchen, Montevideo, and Saintpaul.

Out of the CDC estimated 1.2 million annual cases of illness, about 19,000 of them require hospitalization, and about 450 deaths occur annually. While there are actually two distinct types of illness that can be caused by Salmonella bacteria, nontyphoidal salmonellosis and typhoid fever, nontyphoidal salmonellosis is by far the more common type. In fact, there has not been an outbreak of typhoid fever caused by Salmonella since 1999. Salmonellosis will usually produce symptoms within a 6 to 72 hour window after exposure to the bacteria. The symptoms produced by salmonellosis will generally include headaches, fever, diarrhea, abdominal cramps, nausea, and vomiting. Recovery from a case of Salmonella poisoning will typically start after about a day, but symptoms can last for up to a week. There is a chance that the infection will worsen and cause one of several complications. The most common of these complications is dehydration. Severe dehydration can potentially be very serious, and will often cause hospitalization to be required. Other complications include reactive arthritis and septicemia, also known as blood poisoning. While both of these complications are very serious, they are much less common than dehydration. Those with certain risk factors, including the elderly, children, and others with suppressed immune systems are at an increased risk of developing a more serious case of Salmonellosis. These risk factors also heighten the chance that one of the many complications associated with Salmonella poisoning will occur. Salmonella bacteria can be found in a wide variety of foods and drinks, so it is important to practice proper food safety techniques in order to reduce the chance of infection. Salmonella has been known to cause outbreaks through meats, poultry, eggs, fish, yeast, shrimp, milk, dairy products, spices, coconut, raw egg, peanut butter, fruits, vegetables, and chocolate. If you or a loved one begins to show the symptoms of Salmonella poisoning, contact a medical professional.