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Symptoms and Signs of Salmonella

Doctor's Notes on Salmonella

Salmonella are a group of bacteria that cause diseases in humans (for example, salmonellosis, gastroenteritis, typhoid fever, and paratyphoid fever), animals, and birds. Salmonella are one of the major causes of gastroenteritis in the world and are considered to be the most common cause of food-borne disease (food poisoning) in the U.S.

Symptoms of Salmonella infection usually begin about 12-72 hours after ingestion of the bacteria and include diarrhea, nausea, abdominal cramps, and vomiting. Fever may occur but usually lasts only one to three days, and all symptoms usually resolve in about three to seven days. Some people infected may develop a slow heartbeat or slightly raised red or rose-colored spots (rose spots) on the chest and abdomen. Symptoms of Salmonella infection depend on the overall health of the infected person and the particular strain infecting the patient.

Medical Author: John P. Cunha, DO, FACOEP
Medically Reviewed on 3/11/2019

Salmonella Symptoms

  • The signs and symptoms of Salmonella infections depend on the overall health of the infected person (for example, normal or with a suppressed immune system) and the particular serovar infecting the patient.
  • Signs and symptoms usually begin about 12-72 hours after ingestion of the bacteria. In general, people contract S. spp (for example, serovars S. enteritidis, S. cholerasuis, or non-typhoidal types of the bacteria) that usually cause a self-limiting diarrhea, nausea, abdominal cramps, and vomiting termed salmonellosis or Salmonella gastroenteritis (Salmonella poisoning).
  • Fever may be present but usually lasts only one to three days, with all the signs and symptoms resolving in about three to seven days. This gastroenteritis is not always traced to the bacterial source and is sometimes simply termed "food poisoning," a term used to describe similar symptoms and signs caused by several different bacterial, parasitic, and viral organisms (for example, E. coli, Giardia, and rotavirus). Those with a suppressed immune system, the elderly, neonates, and young children may develop more severe symptoms (for example, bacteremia or sepsis).
  • Fever and the above-mentioned symptoms lasting over seven to 10 days suggest infection with the more virulent serovars, S. typhi or S. paratyphi. S. typhi causes typhoid fever, which includes symptoms of a high fever (104 F), abdominal pains, sweating, and confusion; some of those affected may develop swollen lymph nodes.
  • About half of patients develop a slow heartbeat (bradycardia), and some get slightly raised red or rose-colored spots (rose spots) on the chest and abdomen. S. paratyphi causes paratyphoid fever, a disease similar to but with less severe symptoms than typhoid fever.
  • Some untreated patients who become infected with S. typhi or S. paratyphi and are otherwise healthy will resolve the infection in about one month, but others can suffer complications (for example, becoming a carrier of the organism, developing organ infections, sepsis, and potentially death).

Salmonella Causes

The majority of Salmonella infections are due to ingestion of food or water, although direct contact with animals has become more common as a source of the organisms to cause infection. In people with normal gastrointestinal tracts and immune systems, researchers have estimated that about 1 million to 1 billion organisms need to be ingested to cause infection, because normal human stomach acid can kill large numbers of these bacteria. If some bacteria reach the intestine, the organisms can attach to intestinal cells where Salmonella toxins (cytotoxin and enterotoxin) can damage and kill cells. The intestinal cell damage results in the inability of the body to normally retain and adsorb fluids, so diarrhea results. In some people, the diarrhea can cause serious dehydration. However, the majority of Salmonella-caused infections are then eventually eliminated by the person's immune defenses. Some Salmonella are not eliminated; these bacteria survive the initial immune response by living inside cells (macrophages) of the immune system. The bacteria can sometimes spread to the blood (bacteremia). Some Salmonella (for example, S. typhi) can also enter the gallbladder and remain there. The patient can recover from the disease but still sheds bacteria through the gallbladder secretions (bile) into the feces. This person thus becomes a carrier of Salmonella and potentially can infect many others, especially if the person lives in unsanitary conditions or works in the food-processing industry.

Salmonella Food Poisoning, Salmonellosis, Treatment, Symptoms Slideshow

Salmonella Food Poisoning, Salmonellosis, Treatment, Symptoms Slideshow

Salmonella is an extremely common type of bacteria. These rod-shaped organisms can be found in both cold-blooded and warm-blooded animals across the world. They are also one of the most common causes of sickness in human beings.

Salmonella poisoning can infect people in one of two ways. It is most often spread from animals to people through the food supply. This is how the bacteria can cause the nauseating disease gastroenteritis. Typhoid-causing Salmonella, however, is usually spread from person to person.

In this article, you will learn all about Salmonella. You’ll find out how it can make you sick, how the bacteria are fighting back against antibiotic medicine and what we can do about it, how to keep your grub safe from these illness-causing organisms, and even what happens when Salmonella grows in space.


Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.