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Salmonellosis, or salmonella, is one of the most common foodborne diseases. According to the Centers for Disease Control and Prevention, salmonella causes approximately 1.2 million illnesses in the United States, with 19,000 hospitalizations and 380 deaths.

Salmonella may occur in small, contained outbreaks in the general population or in large outbreaks in hospitals, restaurants, or institutions for children or the elderly.

Children are the most likely to get salmonellosis. The elderly, infants, and those with compromised immune systems are more likely to have a severe illness. People with AIDS are particularly vulnerable, often suffering from recurring episodes.​


Many types of Salmonella bacteria cause salmonellosis in animals and people. While the occurrence of different types of Salmonella varies from country to country, S. typhimurium and S. enteritidis are the two most commonly found in the United States.

Some strains of Salmonella have become resistant to several antibiotics normally used to treat people with salmonella disease, posing a serious public health threat.


Salmonella bacteria can be found in food products such as raw poultry, eggs, and beef, and sometimes on unwashed fruit. Food prepared on surfaces that previously were in contact with raw meat or meat products can, in turn, become contaminated with the bacteria. This is called cross-contamination.

In recent years, the Centers for the Disease Control and Prevention has received reports of several cases of salmonella from eating raw alfalfa sprouts grown in contaminated soil. You also can get salmonella after handling pets, particularly reptiles like snakes, turtles, and lizards.

Salmonella can become a chronic infection even if you do not have symptoms. In addition, though you may have no symptoms, you can spread the disease by not washing your hands before preparing food for others. In fact, if you know you have salmonella, health care experts recommend you do not prepare food or pour water for others until laboratory tests show you no longer carry Salmonella bacteria.


The following symptoms usually begin from 12 hours to 3 days after you are infected:

  • Diarrhea
  • Fever
  • Abdominal cramps
  • Headache

These symptoms, along with possible nausea, loss of appetite, and vomiting, usually last for four to seven days.

Symptoms are most severe in the elderly, infants, and people with chronic conditions such as diabetes or HIV infection.


The Centers for Disease Control and Prevention has ways you can prevent salmonellosis.


Your healthcare provider can use lab tests that will identify Salmonella in your stool if you are infected.


Salmonella infections usually resolve in five to seven days and most do not require treatment other than oral fluids. Those with severe diarrhea, however, may need intravenous fluids. If the disease spreads from the intestines into the bloodstream, healthcare providers can treat it with antibiotics. Some strains of Salmonella have become resistant to several antibiotics normally used to treat people with salmonella disease, posing a serious public health threat.


Reiter’s Syndrome

While most people recover successfully from salmonella, a few may develop a chronic condition called Reiter’s syndrome. This syndrome can last for months or years and can lead to arthritis. Its symptoms are painful joints, irritated eyes, and painful urination.

Unless treated properly, Salmonella bacteria can escape from the intestine and spread by blood to other organs, sometimes leading to death.

Typhoid Fever

S. typhi bacteria can cause typhoid fever, a more serious disease. This disease, which can be fatal if untreated, is not common in the United States. Typhoid fever frequently occurs in developing countries, where it affects about 21.5 million persons each year, typically through contaminated water. According to the Centers for Disease Control and Prevention, it is estimated that about 5,700 cases occur annually, approximately 75 percent of which are acquired while traveling internationally.

Appropriate antibiotics usually are effective for treating typhoid fever, although the number of cases of antibiotic-resistant S. typhi are increasing in some parts of the world.

Currently, two vaccines are available in the United States that are 50 to 80 percent effective in preventing S. typhi. The Typhoid Vaccine Live Oral Ty21a is given orally in several doses to immunize adults and children older than 6 years of age. The Vi capsular polysaccharide vaccine (or ViCPS) is an injected vaccine used in adults and in children over 2 years of age.

Health experts do not recommend routine vaccination with either vaccine in the United States. Vaccination is recommended for travelers visiting areas where there is a risk of getting of S. typhi infection.

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Basic research is helping scientists to better understand how microbes spread by contaminated food or water cause disease in humans.

NIAID-supported researchers are studying the bacterial genes that help pathogens (germs) establish themselves in the human body and cause disease. For example, scientists have identified genes that appear to be involved in signaling certain immune system cells to cause inflammation and may contribute to the development of diarrhea. The genetic characteristics of outbreak strains are also being investigated.

Recently, a NIAID-funded study on the gut inflammation caused by Salmonella typhimurium was named the top paper of 2010 by The Scientist Faculty of 1000. This study found that the infecting bacterium benefits from the host’s immune response, gaining energy from it. Other infectious bacteria may soon be found to behave the same way.

Other NIAID-sponsored research focuses on methods by which the organism grows and interacts in cells. Scientists have discovered that some intestinal bacteria recognize when they are in a human and respond by activating a particular set of powerful genes that enable the organism to live in the body and cause disease. Future studies will define new ways to intervene, whether by prevention or treatment, in the disease process.

Scientists have determined the complete genome (genetic blueprint) sequences for Salmonella typhi, Salmonella typhimurium, Escherichia coli O157:H7, Shigella flexneri, Yersinia enterocolitica,and . Sequencing studies are underway for other harmful strains of these bacteria. Scientists hope this new information will speed the discovery of new targets for treatments and vaccines against foodborne pathogens.

NIAID is also supporting the Systems Biology for EnteroPathogens program, established to deepen researchers’ fundamental understanding of the complex processes of microbes and their interactions with the host. The systems approach involves the use of advanced technologies to analyze, identify, quantify, model, and ultimately predict the overall molecular processes involved in the pathogenesis of Salmonella.

NIAID has awarded four grants to establish the Enteric Research Investigational Network (ERIN), which is designed to bridge gaps between basic and clinical research on bacteria and viruses that gain access to the host via the gastrointestinal tract to cause a variety of diseases.

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Last Updated February 06, 2015

Last Reviewed February 06, 2015