Is Salmonella Contagious?

Salmonella is a genus name that represents gram-negative rod-shaped bacteria that cause disease in humans and other warm-blooded animals. Salmonella can cause various diseases, such as food poisoning, gastrointestinal inflammation, typhoid fever, and sepsis. The CDC estimates that every year in the United States about 1.2 million people are infected with Salmonella, 23,000 need hospital care, and 450 deaths occur.

Many of the members of the bacterial genus Salmonella are contagious. The organisms can be transferred from person to person by both direct (via saliva, fecal/oral spread, kissing) and indirect contact (for example, using contaminated eating utensils). In addition, a number of Salmonella species can be transmitted from animals (snakes, turtles, chickens, hamsters, cats, and dogs) to humans, usually by direct contact. Undercooked meats and especially eggs are common sources of Salmonella bacteria.

Some individuals may shed Salmonella for days to weeks after symptoms have resolved and remain contagious during this time. A few individuals may become carriers and be contagious for years (for example, Typhoid Mary, a food handler responsible for several typhoid outbreaks).

Most symptoms of salmonellosis begin within 12-24 hours after exposure to the bacteria. It is not unusual to have a group of individuals come down with the same symptoms if Salmonella infection comes from contaminated foods. Health care professionals often recognize outbreaks when people who eat or drink from a contaminated source begin to seek medical care (for example, a large family reunion with many people eat contaminated potato salad). The symptoms and signs usually include stomach cramps, diarrhea, fever, and occasionally vomiting. Usually, a physician makes the diagnosis after laboratory examination of the stool sample, because the bacteria can be easily cultivated and identified. However, if the symptoms are relatively mild (for example, no dehydration), by the time the organism is identified, most people will be spontaneously cured of the disease.

Salmonella spread usually through the fecal-oral route (contamination of hands or objects with bacteria shed in the stool); Salmonella can be excreted into the environment and easily contaminate food and water sources. When animals or humans touch or consume food or drink contaminated with Salmonella, they are likely to get salmonellosis. The contaminated animal or human then can easily spread the bacteria to other animals and/or humans by direct and indirect contact.

Salmonellosis for most people is an uncomfortable disease that lasts about three to five days and often requires only good oral fluid intake for recovery. The symptoms gradually wane, and most people spontaneously clear the infection in this time period. However, for other individuals, symptoms of dehydration, nausea, and vomiting may be more severe. Most infected patients do not require antibiotic treatment, although some individuals will require antibiotics to help cure the infection. A few individuals may have very severe symptoms that require the patient to be hospitalized.

If any individual shows signs of dehydration (for example, reduced or absent urination, dry mucus membranes), have immunodeficiency problems, or has sickle cell anemia, he or she should contact a physician urgently or go to an emergency department to avoid complications of severe dehydration and/or sepsis (spread of infection to the bloodstream). People at higher risk for Salmonella infections are infants, young children, and anyone with suppressed immune system function.