Overview

Salmonella infection (salmonellosis) is a common bacterial disease that affects the intestinal tract. Salmonella bacteria typically live in animal and human intestines and are shed through feces. Humans become infected most frequently through contaminated water or food.

Typically, people with salmonella infection have no symptoms. Others develop diarrhea, fever and abdominal cramps within eight to 72 hours. Most healthy people recover within a few days without specific treatment.

In some cases, the diarrhea associated with salmonella infection can be so dehydrating as to require prompt medical attention. Life-threatening complications also may develop if the infection spreads beyond your intestines. Your risk of acquiring salmonella infection is higher if you travel to countries with poor sanitation.

Symptoms

Salmonella infection is usually caused by eating raw or undercooked meat, poultry, eggs or egg products. The incubation period ranges from several hours to two days. Most salmonella infections can be classified as stomach flu (gastroenteritis). Possible signs and symptoms include:

  • Nausea
  • Vomiting
  • Abdominal cramps
  • Diarrhea
  • Fever
  • Chills
  • Headache
  • Blood in the stool

Signs and symptoms of salmonella infection generally last two to seven days. Diarrhea may last up to 10 days, although it may take several months before bowels return to normal.

A few varieties of salmonella bacteria result in typhoid fever, a sometimes deadly disease that is more common in developing countries.

Causes

Salmonella bacteria live in the intestines of people, animals and birds. Most people are infected with salmonella by eating foods that have been contaminated by feces. Commonly infected foods include:

  • Raw meat, poultry and seafood. Feces may get onto raw meat and poultry during the butchering process. Seafood may be contaminated if harvested from contaminated water.
  • Raw eggs. While an egg's shell may seem to be a perfect barrier to contamination, some infected chickens produce eggs that contain salmonella before the shell is even formed. Raw eggs are used in homemade versions of mayonnaise and hollandaise sauce.
  • Fruits and vegetables. Some fresh produce, particularly imported varieties, may be hydrated in the field or washed during processing with water contaminated with salmonella. Contamination also can occur in the kitchen, when juices from raw meat and poultry come into contact with uncooked foods, such as salads.

The Food and Drug Administration also indicates that some salmonella outbreaks have been traced to contaminants in spices. The agency is seeking ways to increase the safety of spices.

Many foods become contaminated when prepared by people who don't wash their hands thoroughly after using the toilet or changing a diaper. Infection also can occur if you touch something that is contaminated, including pets, especially birds and reptiles, and then put your fingers in your mouth.

Risk factors

Factors that may increase your risk of salmonella infection include activities that may bring you into closer contact with salmonella bacteria and health problems that may weaken your resistance to infection in general.

Increased exposure

  • International travel. Salmonella infection, including varieties that cause typhoid fever, is more common in developing countries with poor sanitation.
  • Owning a pet bird or reptile. Some pets, particularly birds and reptiles, can carry salmonella bacteria.

Stomach or bowel disorders

Your body has many natural defenses against salmonella infection. For example, strong stomach acid can kill many types of salmonella bacteria. But some medical problems or medications can short-circuit these natural defenses. Examples include:

  • Antacids. Lowering your stomach's acidity allows more salmonella bacteria to survive.
  • Inflammatory bowel disease. This disorder damages the lining of your intestines, which makes it easier for salmonella bacteria to take hold.
  • Recent use of antibiotics. This can reduce the number of "good" bacteria in your intestines, which may impair your ability to fight off a salmonella infection.

Immune problems

The following medical problems or medications appear to increase your risk of contracting salmonella by impairing your immune system.

  • AIDS
  • Sickle cell disease
  • Malaria
  • Anti-rejection drugs taken after organ transplants
  • Corticosteroids

Complications

Salmonella infection usually isn't life-threatening. However, in certain people — especially infants and young children, older adults, transplant recipients, pregnant women, and people with weakened immune systems — the development of complications can be dangerous.

Dehydration

If you can't drink enough to replace the fluid you're losing from persistent diarrhea, you may become dehydrated. Warning signs include:

  • Decreased urine output
  • Dry mouth and tongue
  • Sunken eyes
  • Reduced production of tears

Bacteremia

If salmonella infection enters your bloodstream (bacteremia), it can infect tissues throughout your body, including:

  • The tissues surrounding your brain and spinal cord (meningitis)
  • The lining of your heart or valves (endocarditis)
  • Your bones or bone marrow (osteomyelitis)
  • The lining of blood vessels, especially if you've had a vascular graft

Reactive arthritis

People who have had salmonella are at higher risk of developing reactive arthritis. Also known as Reiter's syndrome, reactive arthritis typically causes:

  • Eye irritation
  • Painful urination
  • Painful joints

Prevention

The Department of Agriculture has created a Salmonella Action Plan, which involves updating the poultry slaughter inspection system and enhancing sampling and testing programs for poultry and meat. The plan's purpose is to cut the number of salmonella infections in the United States.

You can also take care to avoid spreading bacteria to others. Preventive methods are especially important when preparing food or providing care for infants, older adults and people with weakened immune systems. Be sure to cook food thoroughly and refrigerate or freeze food promptly.

Wash your hands

Washing your hands thoroughly can help prevent the transfer of salmonella bacteria to your mouth or to any food you're preparing. Wash your hands after you:

  • Use the toilet
  • Change a diaper
  • Handle raw meat or poultry
  • Clean up pet feces
  • Touch reptiles or birds

Keep things separate

To prevent cross-contamination:

  • Store raw meat, poultry and seafood away from other foods in your refrigerator
  • If possible, have two cutting boards in your kitchen — one for raw meat and the other for fruits and vegetables
  • Never place cooked food on an unwashed plate that previously held raw meat

Avoid eating raw eggs

Cookie dough, homemade ice cream and eggnog all contain raw eggs. If you must consume raw eggs, make sure they've been pasteurized.

April 08, 2017
References
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  2. Salmonella questions and answers: Food safety information. U.S. Department of Agriculture. http://www.fsis.usda.gov/wps/wcm/connect/abff4b65-494e-45f4-9d69-75e168c8524b/Salmonella_Questions_and_Answers.pdf?MOD=AJPERES. Accessed Nov. 21, 2016.
  3. Salmonella. Centers for Disease Control and Prevention. http://www.cdc.gov/salmonella/. Accessed Nov. 21, 2016.
  4. Oral rehydration therapy. http://www.uptodate.com/home. Accessed Nov. 21, 2016.
  5. Nontyphoidal salmonella infections. Merck Manual Professional Version. https://www.merckmanuals.com/professional/infectious-diseases/gram-negative-bacilli/nontyphoidal-salmonella-infections. Accessed Nov. 21, 2016.
  6. FSIS releases comprehensive strategy to reduce salmonella. U.S. Department of Agriculture Food Safety and Inspection Service. http://www.fsis.usda.gov/wps/portal/fsis/topics/food-safety-education/get-answers/food-safety-fact-sheets/foodborne-illness-and-disease/salmonella/sap. Accessed Nov. 21, 2016.
  7. FDA releases draft risk profile on pathogens and filth in spices, takes steps to strengthen spice safety. U.S. Food and Drug Administration. http://www.fda.gov/Food/NewsEvents/ConstituentUpdates/ucm372995.htm. Accessed Nov. 21, 2016.