Mayo Clinic Health Library

Salmonella infection

Updated: 04-16-2011

Definition

Salmonella infection 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 sources.

Typically, people with salmonella infection 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 salmonella infection is higher if you travel to countries with poor sanitation.

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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 gastroenteritis. Possible signs and symptoms include:

  • Nausea
  • Vomiting
  • Abdominal pain
  • Diarrhea
  • Fever
  • Chills
  • Headache
  • Muscle pains
  • Blood in the stool

Signs and symptoms of salmonella infection generally last four to seven days, although it may take several months for your bowels to return to normal.

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

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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.

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, then put your fingers in your mouth.

Food handlers who return to work before the infection completely clears up can continue to spread the disease. Some people who get salmonella infection become chronic carriers, meaning they continue to excrete the bacteria in their feces or, rarely, urine for a year or more after their signs and symptoms clear up. Some carriers can pass Salmonella infection without having signs or symptoms of the disease.

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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 the 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 be infected with salmonella bacteria.
  • Living in group housing. People who live in college dorms or nursing homes might be at higher risk of infection simply because they are exposed to more people. In addition, food prepared at institutions often uses large amounts of ground meat or unshelled eggs that have been pooled from many different sources. This allows one infected egg or infected hamburger to contaminate the entire batch.

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
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Complications

Salmonella infection itself 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 liquids 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)

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
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Preparing for your appointment

Most people don't need to seek medical attention for a salmonella infection because it clears up on its own within a few days. However, in cases involving infants, young children, and older or immunocompromised adults, call your doctor if the illness lasts more than a few days, is associated with high fever or bloody stools, or if it appears to be causing dehydration.

If you make an appointment with your doctor, it's a good idea to prepare for it. Here's some information to help you.

What you can do

  • Be aware of any pre-appointment restrictions. At the time you make the appointment, be sure to ask if there's anything you need to do in advance, such as restrict your diet.
  • Write down any symptoms you're experiencing, including any that may seem unrelated to the reason for which you scheduled the appointment.
  • Write down key personal information, including any major stresses, recent life changes or recent travel.
  • Make a list of all medications, vitamins or supplements you're taking.
  • Bring a family member or friend along, if possible. Someone who accompanies you may remember information you missed or forgot.
  • Write down questions to ask your doctor.

Preparing a list of questions for your doctor will help you make the most of your time together. List your questions from most important to least important. For salmonella infection, some basic questions to ask your doctor include:

  • What is likely causing my symptoms or condition?
  • Other than the most likely cause, what are other possible causes for my symptoms or condition?
  • What kinds of tests do I need?
  • What is the best course of action?
  • What are the alternatives to the primary approach you're suggesting?
  • I have other health conditions. How can I best manage them together?
  • Are there any restrictions I need to follow?
  • Should I see a specialist?
  • Is there a generic alternative to the medicine you're prescribing?

Don't hesitate to ask any other questions you have.

What to expect from your doctor
Your doctor will need to know:

  • When the illness began
  • The frequency of the vomiting or diarrhea
  • Whether the vomitus or diarrheal stool contains visible bile, mucus or blood
  • If you have a fever
  • If you've recently traveled outside the country

What you can do in the meantime
To prevent dehydration, drink water or suck on ice chips. To prevent dehydration in children, use an oral rehydration solution, such as Pedialyte, unless your doctor advises otherwise.

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Tests and diagnosis

Salmonella infection can be detected by testing a sample of your stool. However, this test may not be very useful because most people have recovered from their symptoms by the time the test results return.

If your doctor suspects that you may have a salmonella infection in your bloodstream, he or she may suggest testing a sample of your blood for the bacteria.

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Treatments and drugs

Medications
Because salmonella infection can be dehydrating, replacement of fluids and electrolytes is the focus of treatment. Severe cases may require hospitalization and fluids delivered directly into a vein (intravenous). In addition, your doctor may recommend:

  • Anti-diarrheals. Medications like loperamide (Imodium) can help relieve cramping, but they may also prolong the diarrhea associated with salmonella infection.
  • Antibiotics. If your doctor suspects that salmonella bacteria have entered your bloodstream, or if you have a severe case or a compromised immune system, he or she may prescribe antibiotics to kill the bacteria. Antibiotics are not of benefit in uncomplicated cases. In fact, antibiotics may prolong the period in which you carry the bacteria and can infect others, and they can increase your risk of relapse.
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Lifestyle and home remedies

Even if you don't need medical attention for your salmonella infection, you need to take care not to dehydrate, a common concern with diarrhea and vomiting. Adults should drink water or suck on ice chips. For children, you can use an oral rehydration solution, such as Pedialyte, unless your doctor advises otherwise.

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Prevention

Salmonella infection is contagious, so take precautions to avoid spreading bacteria to others. Preventive methods are especially important when preparing food or providing care for infants, older adults and people with compromised 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.

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