Salmonella or salmonellosis is an illness of the gastrointestinal tract caused by Salmonella bacteria. It is one of the most common types of food poisoning, which people usually contract by consuming contaminated food or water. The bacteria are common in meat, eggs, and poultry, and some pets carry Salmonella and pass it to their owners. Over one million people each year develop salmonellosis. Serious complications are relatively rare, but salmonella causes approximately 450 deaths annually in the United States. S. typhimurium is a type of salmonella that causes typhoid fever.

Symptom Onset

Most people who contract a salmonella infection do not become ill. If they are affected, their symptoms will begin six to 96 hours after exposure. The combined symptoms of a salmonella infection cause gastroenteritis or inflammation of the gastrointestinal tract, which typically lasts four to seven days. Most people recover without medical intervention, but sometimes the infection causes complications, particularly if the individual has a compromised immune system or underlying illness.

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Nausea is the first and most common symptom of salmonella infection. The body starts fighting infections as soon as it identifies harmful bacteria. Stomach acid production increases to kill the bacteria. The immune system sends phagocytes to attack the invading bacteria as well. These processes occur in the stomach and digestive tract and cause nausea.

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Vomiting occurs shortly after nausea begins, as the body works to expel the invading bacteria, due in part to the increase in stomach acid prompted by the infection. Doctors usually advise people to let vomiting run its course rather than suppressing it with medication. The symptom is a natural reaction that can reduce the duration and severity of salmonellosis if the body successfully expels bacteria before the infection reaches the intestines. However, repeated vomiting and diarrhea can lead to dehydration. If these symptoms persist or dizziness or lightheadedness develop, it is important to seek medical care.

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Salmonella bacteria infect and kill epithelium cells that line the inner surface of the intestines. The dead and damaged cells cause inflammation in the intestines and disturb the normal, healthy bacteria in the intestinal tract. This damage triggers diarrhea that may contain mucus or blood. This process is part of the bacterium's life cycle. The body expels Salmonella bacterium along with loose and watery stools. It is essential to practice good hygiene when infected, as the bacteria in contaminated stool can infect other people or animals.

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Fevers occur during salmonellosis as a part of the body's immune response to harmful bacteria. Fevers elevate body temperature by two to seven degrees Fahrenheit. This inhibits bacterial growth and makes the body a less favorable environment for bacteria overall. Fevers also enhance the ability of certain immune cells to fight invading bacteria and contain the infection.

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Dehydration is a secondary symptom of salmonellosis; it is not caused by the bacterium directly. The body loses fluids and electrolytes through diarrhea and vomiting. Additionally, people frequently avoid eating and drinking when they feel nauseous, and it is difficult to drink enough to stay hydrated when the body violently loses fluids for multiple days.

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Abdominal Pain

Mild to severe abdominal pain is a common symptom of salmonella, caused by inflammation in the intestines and loose stools. Increased bile production and excessive stomach acid triggered by bacteria in the stomach may cause stomach pain or acid reflux. Frequent vomiting and diarrhea can lead to strained muscles or spasms in the abdomen and lower back.

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Headaches and Muscle Aches

Headaches and muscle aches are secondary symptoms of salmonellosis, often caused by dehydration and fever. Low blood sugar from nausea and vomiting or general fatigue can also cause headaches, and the bacteria sometimes produce toxins that contribute to muscle pain. Muscle soreness can also result from diarrhea, vomiting, and bacteria-produced toxins.

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Reactive Arthritis

Reactive arthritis is a rare complication that occurs in six to 30% of all Salmonella infections. The reactive arthritis "triad" includes arthritis, conjunctivitis, and urethritis, which lead to inflammation in the joints, eye irritation, and burning during urination. Symptoms of reactive arthritis appear weeks to months after exposure to the bacteria. The cause of this complication is not entirely understood, but it is associated with foodborne bacterial infections. Some experts theorize that reactive arthritis is an autoimmune disorder triggered by an excessive immune response to food poisoning.

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Sepsis is a systemic infection that affects the entire body. The strains of Salmonella responsible for typhoid fever are the most likely to cause sepsis, but systemic infection can occur with other strains too. Sepsis as a result of salmonellosis is most likely to develop in people with compromised immune systems. The bacteria can also escape the gastrointestinal tract if severe inflammation in the intestines causes a bowel perforation.

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