Have you ever had "food poisoning?" Food poisoning is the common term many people use to refer to foodborne illness. When an outbreak occurs, Salmonella bacteria are very likely the cause since this is one of the most common types of foodborne illnesses reported. There is a large group of bacteria that are called Salmonella. They are microscopic creatures, and if present in food do not usually affect taste, smell, or appearance of the food. Salmonella serotype Typhimurium and Salmonella serotype Enteritidis are two common types that cause foodborne illnesses.
What are the symptoms?
Infections with Salmonella spp. are called salmonellosis. In mild cases, the symptoms are very similar to the flu and include abdominal pain, headache, nausea, vomiting, fever, and diarrhea. Mild cases can resolve with home care and fluids to prevent dehydration. Severe cases may require hospitalization because of chronic diarrhea. The bacteria can enter the bloodstream or spinal fluid and may require treatment with antibiotics. Even after recovery, the diarrhea may continue for several months. A few people who have salmonellosis may develop long-term joint pain, a condition called Reiter's syndrome. In extreme cases, this could lead to chronic arthritis.
Public health consequences
The exact number of salmonellosis cases that occur each year is hard to determine because many people attribute their illness to a virus or flu. The local Health Department and Centers for Disease Control and Prevention (CDC) cannot record the number of cases accurately unless the ill person seeks medical care, which is not usual in mild cases. The CDC estimates the number of cases of salmonellosis based on corrections for under reporting, misdiagnosis, and the number of cases that are not caused by contaminated food.
The CDC estimates that there are over 1 million cases of salmonellosis each year in this country, and that 94% of the cases are caused by eating contaminated food. Almost 20,000 cases will be severe enough to require hospitalization; 378 deaths are possible each year. Because the number of Salmonella-linked cases has not declined over the last decade, the CDC has suggested that public health educators increase efforts to educate the public on ways to control this foodborne illness.
Most cases occur in young children less than 5 years old (69.5 cases/100,000 population), but the age group that has the most severe illnesses requiring hospitalization, and perhaps causing death, are the elderly over the age of 60 years (17.0 cases/100,000 population). Young children are susceptible due to their immature immune systems. Likewise, the elderly are susceptible because of aging and also because of the incidence of other chronic diseases that affect the immune system.
Where does the Salmonella come from?
Since the incubation period for the Salmonella bacteria is 8 to 72 hours it is often hard to trace back to the food that was eaten. Foods usually involved in salmonellosis are poultry and poultry salads, meat and meat products, raw milk, shell eggs, egg custards, improperly cooked mayonnaise, ice cream, sauces, seafood, not properly washed fruits and vegetables, and other protein foods. At one time it was believed that cracked shells were the only way salmonella bacteria contaminated eggs. However, salmonella has been found in infected, but otherwise healthy hens and their uncracked eggs.
Is food the only source?
Salmonella can also be found in domestic and wild animals and even in the intestinal tract of people. Contaminated feces from either animals or people can be transferred to food that is eaten by people, causing the infections to be passed along. It is important to keep pets out of the kitchen when preparing food and to wash hands thoroughly for this reason.
Turtles, iguanas, and lizards are growing in popularity as pets. They are also carriers of Salmonella. Children under the age of five should not have direct contact with turtles, iguanas, and other reptiles. Young children have an increased risk for reptile-associated salmonellosis and complications such as meningitis (infection of the spinal fluid).
How can you control Salmonella in your home?
1. Avoid eating foods containing raw eggs.
- Use pasteurized eggs in foods containing raw eggs that will not be cooked.
- Cook eggs until both the yolk and white are firm and eat promptly after cooking.
- Promptly refrigerate foods prepared with eggs or poultry.
- Refrigerate food in shallow containers within 2 hours of preparation.
2. Knives, cutting boards, and food preparation surfaces should be washed with hot water and soap after contact with raw poultry, meat, and seafood.
- Clean sinks and counters with paper towels or clean cloths and hot soapy water before and after cooking food.
- Keep foods that are ready to eat away from raw poultry.
- Wash knives, cutting boards, and counters with hot water and soap after you work with raw chicken or turkey.
- Scrub your cutting board with dish soap. If your cutting board is not made of wood, you can put it into the dishwasher.
- Wash your hands with soap and warm water after working with raw poultry.
- Put thawing chicken or turkey in a dish in the refrigerator to keep juices from leaking on the food below.
3. Use a thermometer to make sure that meat, poultry (including ground), and foods containing eggs are cooked to safe temperatures, at least 160 degrees F.
- The only way to be sure meat and chicken are done is to check with a food thermometer.
- Follow the safe cooking advice on packages.
- The thermometer should go into the thickest part of the chicken or turkey.
- Cook poultry until the food thermometer says at least 160 degrees F.
- Cook eggs until both the yolk and white are firm.
- Any foods that have eggs should be checked with a food thermometer to be sure they are done and ready to eat.
4. Drink only pasteurized milk.
- Children and the elderly are very susceptible to salmonellosis and should not drink raw milk.
- Only buy cheeses made with pasteurized milk, or that have been aged a minimum of 60 days.
5. Wash hands with warm, soapy water before and after handling raw foods.
- First, wet your hands.
- Add soap to your hands.
- Rub both sides for at least 20 seconds.
- Rinse thoroughly.
- Air dry, or dry your hands with a clean towel or paper towel.
- Always wash your hands after using the toilet, after changing a baby's diaper, after touching pets or other animals, and after sneezing or coughing.
6. Use proper refrigeration.
- Foods should be kept safe at home with prompt and proper refrigeration in a shallow container.
- Perishable, prepared food/leftovers should be properly refrigerated or frozen.
- Thoroughly wash fruits and vegetables.
- Thaw foods in the refrigerator, in cold water, or in the microwave—do not thaw at room temperature.
Centers for Disease Control and Prevention. Salmonellosis. www.cdc.gov/nczved/divisions/dfbmd/diseases/salmonellosis/. Accessed: February 14, 2011.
Centers for Disease Control and Prevention. Vital signs: Incidence and trends of infection with pathogens transmitted commonly through food—foodborne diseases active surveillance network, 10 U.S. sites, 1996–2010. Morbidity and Mortality Weekly 2011; 60 (22): 749–755.
Hillers, V.N., Medeiros, L.C., Kendall, P., Chen, G., & DiMascola, S. Consumer food handling behaviors associated with prevention of 13 foodborne illnesses. Journal of Food Protection 2003; 66: 1893–1899.
Scallan, E., Hoekstra, R.M., Angulo, F.J., Tauxe, R.V., Widdowson, M.A., Roy, S.L., Jones, J.L., & Griffin, P.M. Foodborne illness acquired in the United States—major pathogens. Emerging Infectious Diseases 2011; 17: 7–15.
U.S. Food and Drug Administration. Salmonella spp. The Bad Bug Book. www.fda.gov. Accessed: February 11, 2010.
For more information about food safety, visit Foodsafety.osu.edu.