Salmonellosis: Causes, Symptoms, and Prevention

Salmonellosis is one of the most widespread foodborne infections across the globe. It is caused by bacteria belonging to the genus Salmonella, which naturally reside in the intestinal tracts of humans, animals, and birds. Every year, this infection affects millions of people – many of whom never even get a formal diagnosis. According to CDC estimates, Salmonella causes over 1.35 million foodborne illnesses, around 26,500 hospitalizations, and approximately 420 deaths annually in the United States alone. Globally, the numbers are staggering – research published in Clinical Infectious Diseases estimates roughly 93.8 million cases of Salmonella gastroenteritis and 155,000 deaths each year worldwide.

What is salmonellosis? 🔗

Salmonellosis is a gastrointestinal infection caused by Salmonella bacteria. The Salmonella family includes over 2,500 identified serotypes, though fewer than 100 are responsible for the majority of human illness. Two serotypes – Salmonella Enteritidis and Salmonella Typhimurium – are the most common culprits behind infections in the United States and many other countries, as noted by the USDA Food Safety and Inspection Service.

Salmonella belongs to the family Enterobacteriaceae. These are gram-negative, rod-shaped bacilli that inhabit the intestinal tracts of a wide range of hosts – from poultry and cattle to reptiles and humans. One of the tricky aspects of Salmonella contamination is that contaminated food usually looks, smells, and tastes completely normal, making it impossible to detect without laboratory testing.

How does Salmonella spread? 🔗

The primary route of Salmonella transmission to humans is through the consumption of food or water contaminated with animal or human feces. There are several key pathways through which this happens.

Contaminated food products 🔗

The most common source of salmonellosis is undercooked or improperly handled food of animal origin. This includes raw or undercooked poultry, meat, seafood, and eggs. According to the U.S. FoodSafety.gov, about 1 in every 25 packages of chicken at grocery stores is contaminated with Salmonella. Eggs are another major vehicle – Salmonella can be present on the eggshell and can even be found inside the egg before the shell is formed, particularly if the laying hen is infected.

Beyond animal products, outbreaks have been traced to fruits, vegetables, nut butters, frozen foods, and even spices. Unpasteurized milk and dairy products also carry a notable risk since the pasteurization process is specifically designed to eliminate harmful bacteria like Salmonella.

Cross-contamination 🔗

Cross-contamination occurs when juices or residues from raw meat or poultry come into contact with ready-to-eat foods such as salads, bread, or fresh produce. This can happen on cutting boards, countertops, utensils, or even through the hands of a food handler. The U.S. FDA highlights that food handlers who do not wash their hands or sanitize surfaces between preparation steps are a significant source of contamination.

Animal contact 🔗

Salmonella can also spread directly from animals to people. Reptiles such as turtles, iguanas, and lizards are particularly likely to carry the bacteria. Pet birds, chicks, hedgehogs, and even guinea pigs have been linked to salmonellosis outbreaks. People who handle these animals and then touch food or their mouths without washing their hands are at risk of infection.

Symptoms of salmonellosis 🔗

Most people infected with Salmonella develop noticeable symptoms within 6 to 72 hours after consuming contaminated food or water, though in some cases, it can take up to two weeks. The illness typically lasts between 4 and 7 days, and the majority of healthy individuals recover without needing any specific medical treatment.

Common symptoms 🔗

The hallmark symptoms of salmonellosis include:

Diarrhea – often watery, and in some cases bloody. Abdominal cramps – ranging from mild discomfort to severe pain. Fever – usually moderate. Nausea and vomiting – particularly during the early stages. Additional symptoms may include chills and headache. According to the Mayo Clinic, diarrhea may persist for up to 10 days, and it can take several months for normal bowel habits to fully return.

Who is at higher risk? 🔗

While anyone can get salmonellosis, certain groups face a higher risk of both infection and severe illness. These include children under 5 years of age (especially infants under 1 year), adults over 65, pregnant women, and individuals with weakened immune systems – such as those undergoing chemotherapy, living with HIV/AIDS, or managing conditions like diabetes and kidney disease. For these populations, Salmonella can sometimes enter the bloodstream and cause life-threatening complications that require hospitalization and antibiotic treatment.

Diagnosis and treatment 🔗

Salmonellosis is typically diagnosed through a laboratory test on a stool sample. In cases where the infection is suspected to have spread beyond the intestines, blood tests may also be performed.

Treatment approach 🔗

For most healthy individuals, treatment focuses on managing symptoms – staying hydrated is the most critical step, since diarrhea and vomiting can lead to significant fluid loss. Drinking oral rehydration solutions, water, and clear broths is recommended. Rest and a bland diet also help during recovery.

Antibiotics are generally not required for uncomplicated cases and are, in fact, not recommended for mild infections because they may prolong the period during which the person carries and sheds the bacteria. However, antibiotics become necessary for severe infections, bloodstream involvement, or when the patient belongs to a high-risk group. It is worth noting that antibiotic resistance is increasing among Salmonella strains, which limits treatment options in some cases and makes prevention even more important.

Prevention of salmonellosis 🔗

The good news is that salmonellosis is largely preventable. The USDA and other food safety agencies recommend a comprehensive approach summarized by four key principles: Clean, Separate, Cook, and Chill.

Clean: wash hands and surfaces often 🔗

Thorough handwashing with soap and warm water for at least 20 seconds is essential – before and after handling food, after using the bathroom, after changing diapers, and after touching animals or their environments. Cutting boards, utensils, dishes, and countertops should be washed with hot, soapy water after preparing each food item and before moving on to the next.

Separate: avoid cross-contamination 🔗

Raw meat, poultry, seafood, and eggs should always be kept separate from other foods – in the shopping cart, in the refrigerator, and during preparation. Use separate cutting boards for raw meat and for produce or ready-to-eat items. Importantly, the USDA advises against washing raw poultry before cooking, as this can actually splash bacteria onto nearby surfaces and foods.

Cook: reach safe internal temperatures 🔗

Cooking food to the correct internal temperature is the most reliable way to destroy Salmonella. A food thermometer is the only accurate tool for checking this. The recommended safe minimum temperatures are: 165°F (74°C) for all poultry, including ground chicken and turkey; 160°F (71°C) for ground beef, pork, lamb, and veal, as well as egg dishes without meat; 145°F (63°C) for whole cuts of beef, pork, lamb, veal, and fish, with a three-minute rest time after cooking. Eggs should be cooked until both the yolk and white are firm.

Chill: refrigerate promptly 🔗

Bacteria multiply rapidly in the “Danger Zone” – the temperature range between 40°F and 140°F (4°C to 60°C). Perishable foods should never be left at room temperature for more than two hours (or more than one hour if the ambient temperature exceeds 90°F/32°C). Refrigerators should be set to 40°F (4°C) or below. Leftovers should be divided into shallow containers for faster cooling and refrigerated promptly. Frozen foods should always be thawed in the refrigerator, under cold running water, or in the microwave – never on the countertop at room temperature.

Safe handling of eggs and dairy 🔗

Eggs should be purchased from stores that keep them refrigerated and should be stored in the main compartment of the refrigerator rather than on the door. Cracked eggs should be discarded. Raw or undercooked eggs – as found in homemade mayonnaise, hollandaise sauce, or raw cookie dough – pose a real risk. Using pasteurized eggs for recipes that call for raw or lightly cooked eggs is a safer alternative, as recommended by FoodSafety.gov. Similarly, only pasteurized milk and dairy products should be consumed.

Safe interaction with animals 🔗

Anyone who handles reptiles, baby chicks, ducklings, or other animals that commonly carry Salmonella should wash their hands thoroughly with soap and water immediately afterward. Animals should be kept away from kitchen areas and food preparation surfaces. Even pets with diarrhea may shed Salmonella in their feces, so hand hygiene after cleaning pet areas is essential.

The role of food processing and regulation 🔗

Prevention does not rest solely on consumers. A comprehensive farm-to-table approach is necessary to minimize salmonellosis risks. At the farm level, proper biosecurity, regular screening of livestock and poultry for Salmonella, and sanitary processing conditions are critical. According to a review published in Antibiotics (PMC), controlling Salmonella in farm settings depends on good management practices and identifying the primary sources of infection and methods of transmission within the production chain.

At the regulatory level, agencies like the USDA’s Food Safety and Inspection Service (FSIS) enforce standards by collecting product samples from processing plants and testing them for Salmonella. The Hazard Analysis and Critical Control Points (HACCP) system requires meat and poultry processing establishments to have science-based procedures to reduce bacterial contamination. Retailers and food service workers also play a vital role in maintaining cold chain integrity, preventing cross-contamination, and ensuring cooked foods reach safe temperatures.

Global public health significance 🔗

Salmonellosis remains a significant public health burden worldwide. The World Health Organization identifies Salmonella as one of the four key global causes of diarrheal disease. The economic cost is equally substantial – in the United States alone, salmonellosis-related illnesses are estimated to cost approximately $3.3 billion annually, ranking it among the most expensive foodborne infections.

The growing challenge of antimicrobial resistance (AMR) in Salmonella strains adds another layer of urgency. Multidrug-resistant strains have been reported globally, making some infections harder to treat. This underscores the need for prudent antibiotic use in both human medicine and animal agriculture, alongside stronger investment in food safety infrastructure, surveillance, and public education.

What do you think? Given that Salmonella-contaminated food often looks and smells perfectly normal, how can consumers develop better habits around food thermometer use and kitchen hygiene? And in developing countries where cold chain infrastructure is limited, what practical steps could make the biggest difference in reducing salmonellosis?

References

1. https://www.cdc.gov/salmonella/about/index.html
2. https://academic.oup.com/cid/article/50/6/882/419872
3. https://www.fsis.usda.gov/food-safety/foodborne-illness-and-disease/illnesses-and-pathogens/salmonella
4. https://www.foodsafety.gov/blog/salmonella-and-food
5. https://www.fda.gov/food/foodborne-pathogens/salmonella-salmonellosis
6. https://www.mayoclinic.org/diseases-conditions/salmonella/symptoms-causes/syc-20355329
7. https://www.fsis.usda.gov/food-safety/safe-food-handling-and-preparation/food-safety-basics/safe-temperature-chart
8. https://www.foodsafety.gov/blog/salmonella-and-eggs
9. https://pmc.ncbi.nlm.nih.gov/articles/PMC10812683/
10. https://www.who.int/activities/estimating-the-burden-of-foodborne-diseases