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 stool (feces). Humans become infected most frequently through contaminated water or food.

Some people with salmonella infection have no symptoms. Most people develop diarrhea, fever and stomach (abdominal) cramps within 8 to 72 hours after exposure. Most healthy people recover within a few days to a week without specific treatment.

In some cases, diarrhea can cause severe dehydration and requires prompt medical attention. Life-threatening complications also may develop if the infection spreads beyond the intestines. The risk of getting salmonella infection is higher with travel to countries without clean drinking water and proper sewage disposal.

Salmonella infection is usually caused by eating raw or undercooked meat, poultry, and eggs or egg products or by drinking unpasteurized milk. The incubation period — the time between exposure and illness — can be 6 hours to 6 days. Often, people who have salmonella infection think they have the stomach flu.

Possible signs and symptoms of salmonella infection include:

• Diarrhea
• Stomach (abdominal) cramps
• Fever
• Nausea
• Vomiting
• Chills
• Headache
• Blood in the stool

Signs and symptoms of salmonella infection generally last a few days to a week. Diarrhea may last up to 10 days, but it may take several months before bowels return to usual stool habits.

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

Most people don't need to seek medical attention for salmonella infection because it clears up on its own within a few days.

However, if the affected person is an infant, young child, older adult or someone with a weakened immune system, call a health care provider if illness:

• Lasts more than a few days
• Is associated with high fever or bloody stools
• Appears to be causing dehydration, with signs such as such as urinating less than usual, dark-colored urine and having a dry mouth and tongue

Salmonella bacteria live in the intestines of people, animals and birds. Most people are infected with salmonella by consuming food or water that has been contaminated by feces.

Infected food and water

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 or undercooked 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 foods such as mayonnaise and hollandaise sauce.
• Unpasteurized dairy products. Unpasteurized milk and milk products — sometimes called raw milk — may be contaminated with salmonella. The pasteurization process kills harmful bacteria, including salmonella.
• Fruits and vegetables. Some fresh produce, particularly imported varieties, may be irrigated in the field or washed during processing with water contaminated with salmonella. Contamination can also occur in the kitchen, when juices from raw meat and poultry come into contact with uncooked foods, such as salads.

Improperly handled food

Many foods become contaminated when prepared by people who don't wash their hands thoroughly after using the toilet or changing a diaper or after handling contaminated food.

Infected surfaces

Infection can also occur if people touch something that is contaminated and then put their fingers in their mouths.

Infected pets and other animals

Animals and pets, especially birds and reptiles, may carry salmonella bacteria on their feathers, fur or skin or in their feces. Some pet foods may be contaminated with salmonella and can infect animals.

Factors that may increase your risk of salmonella infection include:

• Activities that may bring you into closer contact with salmonella bacteria
• 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, handling or petting animals. Some animals, particularly birds and reptiles, can carry salmonella bacteria. Salmonella can also be found in animal pens, tanks, cages and litter boxes.

Stomach or bowel disorders

The 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 the 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

Some medical problems or medications appear to increase your risk of catching salmonella by weakening your immune system. This interferes with your body's ability to fight infection and disease. Examples include:

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

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 diarrhea, you may become dehydrated. Warning signs include:

• Urinating less than usual or dark-colored urine
• Dry mouth and tongue
• Sunken eyes
• No tears when crying
• Being more tired than usual
• Irritability or confusion

Bacteremia

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

• The urinary system (urinary tract infection)
• The tissues surrounding the brain and spinal cord (meningitis)
• The lining of the heart or valves (endocarditis)
• The bones or bone marrow (osteomyelitis)
• The lining of blood vessels, especially if you've had a vascular graft, such as heart vessel bypass surgery

Reactive arthritis

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

• Eye irritation
• Painful urination
• Painful joints

The U.S. Department of Agriculture (USDA) oversees and updates inspection, sampling and testing programs for poultry and meat. The purpose is to cut the number of salmonella infections in the United States.

You can avoid getting salmonella and spreading bacteria to others in several ways, including safely preparing food, hand-washing, avoiding contamination, and not eating raw meat, dairy or egg products.

Preventive methods are especially important when preparing food or providing care for infants, older adults and people with weakened immune systems.

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 with soap and water for 20 seconds after you:

• Use the toilet
• Change a diaper
• Handle raw meat or poultry
• Clean up pet feces
• Touch pets or other animals and their habitats, especially 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
• Wash food preparation surfaces thoroughly with soap and water

Avoid eating raw eggs

Homemade cookie dough, ice cream, mayonnaise, hollandaise sauce and eggnog all contain raw eggs. If you must consume raw eggs, make sure they've been pasteurized.

Cook and store food properly

Be sure to cook food thoroughly and refrigerate or freeze food promptly.

Salmonella infection is usually diagnosed based on signs and symptoms.

Salmonella infection can be detected by testing a stool sample. However, most people have recovered from their symptoms by the time the test results return.

If your health care provider suspects that you have a salmonella infection in your bloodstream, testing a sample of your blood for the bacteria may be needed.

Most healthy people recover within a few days to a week without specific treatment. Preventing dehydration with adequate fluid intake can help you recover.

Treating dehydration

Because salmonella infection can cause dehydration, treatment focuses on replacing lost fluids and electrolytes — minerals that balance the amount of water in the body.

If dehydration is severe, emergency room care or hospitalization may be needed so that fluids can be delivered directly into a vein (intravenous).

Medications

In addition to advising you to drink plenty of fluids, your health care provider may recommend:

• Anti-diarrheals. Medications such as loperamide (Imodium A-D) can help relieve cramping from diarrhea. However, they may also prolong the diarrhea associated with salmonella infection.

• Antibiotics. Your health care provider may prescribe antibiotics to kill the bacteria. These are usually given if your provider suspects that salmonella bacteria have entered your bloodstream, your infection is severe or you have a weakened immune system.

  Antibiotics are not helpful in most cases of salmonella infection. In fact, antibiotics may extend the period in which you carry the bacteria and can infect others. They can also increase your risk of getting infected again (relapse).

Even if you don't need medical attention for your salmonella infection, you need to take care not to become dehydrated, a common concern with diarrhea and vomiting.

• Most adults with mild to moderate dehydration from diarrhea, vomiting or fever can improve their condition by drinking more water or other liquids. Diarrhea may be worsened by full-strength fruit juice and soft drinks.
• For infants and children who have become dehydrated from diarrhea, vomiting or fever, use oral rehydration solutions that you can buy without a prescription. These solutions contain water and salts in specific proportions to replenish both fluids and electrolytes.

If you make an appointment with your health care provider, here's some information to help you get ready.

You may want to bring a family member or friend along, if possible. Someone who goes with you may remember information you missed or forgot.

What you can do

Before your appointment:

• Find out about any pre-appointment restrictions. When you make the appointment, ask if there's anything you need to do in advance, such as restrict your diet.
• Make a list of your symptoms, including any that may seem unrelated to the reason you scheduled the appointment.
• Make a list of key personal information, including major stresses, recent life changes or recent travel.
• Make a list of all medications, vitamins, herbs or supplements you're taking, and the dosages.
• Make a list of questions to ask your health care provider.

Some basic questions to ask include:

• What is likely causing my symptoms?
• Other than the most likely cause, what are other possible causes for my symptoms?
• What tests do I need?
• What is the best course of action?
• What are 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?
• If medication is prescribed, is there a generic alternative?

Don't hesitate to ask any other questions.

What to expect from your doctor

Your health care provider will need to know:

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

Being prepared to answer questions will help you make the most of your appointment time.