The term Salmonella refers to a group of bacteria that cause Salmonella infection, or salmonellosis, in the intestinal tract.
Salmonella poisoning is often linked to contaminated water or foods, especially meat, poultry, and eggs. Symptoms include abdominal cramps, diarrhea, and vomiting, which tend to appear 12 to 72 hours after infection.
Most people recover after 4 to 7 days without treatment, but a person with severe diarrhea may need hospital treatment.
Apart from food and water, transmission has been linked to pet reptiles. From March through August 2017, a multistate outbreak of Salmonella affected at least 33 people in 13 states, of whom 16 were hospitalized and 12 were under 5 years of age. The outbreak was linked to contact with pet turtles.
Fast facts on salmonella
Here are some key points about salmonella. More detail is in the main article.
- Salmonella poisoning affects around 1.4 million Americans each year and is responsible for almost half the bacterial infections in the United States (U.S.).
- Infection mostly spreads through contaminated water and food.
- Symptoms normally include chills, diarrhea, and fever.
- The illness usually goes away on its own, but severe cases may need hospital treatment.
- Prevention tips include regular handwashing, ensuring all food is well cooked and carefully stored, and not keeping pet reptiles in the home.
Salmonella are gram-negative, rod-shaped bacilli that can cause salmonellosis, a diarrheal illness in humans.
Gram-negative bacteria usually have a cell wall composed of a thin layer of peptidoglycan, covered by a membrane.
There are over 2,300 subtypes of the Salmonella enterica bacterium, including serovars enterititis, Salmonella Agbeni, and typhimurium.
The bacteria live in the gut of infected humans and animals. Some animal and human strains can make humans sick.
Salmonella is a major cause of human bacterial infections in the United States (U.S.). According to the Centers for Disease Control and Prevention (CDC), it affects around 1 million Americans every year, leading to 19,000 hospitalizations and 380 deaths.
Below is a 3-D model of Salmonella enterica, which is fully interactive.
Explore the model using your mouse pad or touchscreen to understand more about Salmonella enterica.
There are thousands of subtypes of Salmonella bacteria, but only about 12 that make people ill, usually with gastroenteritis.
Signs and symptoms of salmonella-induced gastroenteritis include:
- stomach cramps
- bloody stools
- muscle pains
Salmonella bacteria live in the intestines of birds, animals, and humans. Most human infections are caused by eating food or drinking water that has been contaminated by feces.
Foods most commonly infected are:
Uncooked meat, seafood and poultry: Contamination most commonly occurs during the slaughtering process. Harvesting seafood in contaminated waters is a common cause.
Uncooked eggs: Eggs from an infected chicken may contain bacteria. The U.S. Food and Drug Administration (FDA) estimate that, every year, there are 79,000 cases of foodborne illness in the U.S., due to eating eggs containing salmonella. Raw eggs are found in some types of mayonnaise and homemade sauces.
Fruits and vegetables: These may be contaminated if they have been watered or washed in contaminated water. Fruits and vegetables can become contaminated if a person handles raw meat and then touches the fruit without washing their hands.
Other causes include:
Lack of hygiene: Common causes of contamination and infection include kitchen surfaces that are not kept clean, and not washing hands during food preparation, after using the bathroom, or after changing a baby's diapers. A person with contaminated hands can pass the infection on to other people by touching them, or by touching surfaces that others then touch.
Keeping pet reptiles or amphibians: Most reptiles and amphibians carry Salmonella in their gut without becoming ill. They shed the bacteria in their droppings. These can quickly spread onto their skin and then anything they come into contact with, including cages, toys, clothes, furniture, and household surfaces.
Pet reptiles should not be kept indoors if there are children under 5 years of age, pregnant women, older people, or people with a weakened immune system in the household.
Since 1975, the FDA have banned the sale and distribution of small turtles, because of the risk of Salmonella infection.
Young children should not be allowed to handle reptiles or chicks and young birds. Breastfeeding is the safest type of nutrition for young infants.
During pregnancy, complications include dehydration and bacteremia, or bacteria in the blood. This can lead to meningitis. Salmonella can also pass to the fetus. The infant may have diarrhea and fever after birth and a risk of developing meningitis.
Salmonella infection is more common in summer than in winter.
The doctor will ask about symptoms, any other existing conditions, changes in diet or food preparation habits, contact with pets, and travel destinations to try to find out the cause of the problem.
Diarrhea and vomiting are normally a clear indication of gastroenteritis.
Blood and stool tests can help determine the cause of infection.
Symptoms of Salmonella-induced gastroenteritis normally disappear without treatment after around a week.
Fluid: The patient needs to take plenty of fluid to prevent dehydration.
Antibiotics: These may not help in uncomplicated gastroenteritis. The doctor may prescribe them if symptoms are severe, or if bacteria have entered or could enter the bloodstream. Using antibiotics can lead to antibiotic resistance and the risk of the infection returning.
Antimotility drugs: These can stop diarrhea. They reduce cramping, but they may cause the diarrhea to last longer.
Good hygiene is key to preventing salmonella infection.
Washing hands frequently with soap and warm water or using hand sanitizer. This is especially important:
- before preparing or eating food
- after using the bathroom
- after changing a baby's diapers
- after touching pets and other animals
- after gardening
Food handling tips
When dealing with food:
- Keep cooked and raw foods separate.
- Store raw foods in a fridge on the shelves below ready-to-eat foods.
- Wash raw fruits and vegetables thoroughly before eating.
- Cook food through, especially meats and eggs.
- Keep all cooking utensils and work surfaces clean.
- Regularly replace used dishcloths with clean ones.
- Avoid drinking untreated water, for example, from streams, rivers, and lakes.
Salmonella can live for some time in different kinds of food. In 2015, researchers found that the bacteria can live in sandwich cookies and crackers for at least 6 months.
When buying eggs, consumers should make sure they come from a supplier that keeps them refrigerated, and store them at a maximum of 40 degrees Fahrenheit (4 degrees Celsius). Any cracked or dirty eggs should be thrown away.
The FDA require any boxes of eggs that have not been treated for salmonella by pasteurization to carry this warning:
"Safe Handling Instructions: To prevent illness from bacteria: keep eggs refrigerated, cook eggs until yolks are firm, and cook foods containing eggs thoroughly."
The FDA offer detailed advice on how to store eggs, how long to keep them, and so on.
Do not keep pet reptiles or amphibians inside the house if there are older people, pregnant women, very young children, or people with weakened immune systems in the household.
What to do if someone has salmonella poisoning
If somebody in the household becomes infected with Salmonella:
- wash all dirty clothes, bedding, and towels in the washing machine at the hottest setting possible
- thoroughly clean toilet seats, toilet bowls, all handles in the bathroom, basins and taps after use, with a detergent and hot water, followed by a household disinfectant
If the person has a high fever, they should see a doctor. Older people, infants, and people with a compromised immune system are more at risk of a severe infection.