Foodborne Diseases: Causes and Prevention

Every year, millions of people around the world fall sick after eating food that looks, smells, and tastes perfectly fine. According to the World Health Organization (WHO), roughly 600 million people – nearly 1 in 10 globally – suffer from foodborne illnesses annually, leading to about 420,000 deaths. In the United States alone, the Centers for Disease Control and Prevention (CDC) estimates 48 million cases, 128,000 hospitalizations, and 3,000 deaths each year from contaminated food. These numbers make one thing clear: understanding how foodborne diseases work – and how to prevent them – is essential knowledge, not just for food scientists, but for everyone.

What are foodborne diseases? 🔗

A foodborne disease is any illness that results from eating food contaminated with harmful microorganisms – bacteria, viruses, or parasites – or their toxins. Sometimes called food poisoning, these illnesses can range from mild stomach discomfort lasting a day to severe, life-threatening conditions requiring hospitalization.

Common symptoms include diarrhea, vomiting, nausea, abdominal cramps, and fever. The onset of symptoms can vary from as little as 30 minutes to several days after consuming contaminated food, depending on the causative agent. While most healthy adults recover without medical treatment, certain groups face a much higher risk of serious complications. These high-risk groups include infants, young children, pregnant women, older adults, and individuals with weakened immune systems due to conditions like HIV/AIDS, cancer, or diabetes.

Foodborne infection vs. foodborne intoxication 🔗

Foodborne diseases are broadly classified into two categories: infections and intoxications. Understanding the difference between the two is crucial because their mechanisms, onset times, and management strategies differ significantly.

Foodborne infections 🔗

A foodborne infection occurs when a person ingests food containing live pathogenic microorganisms – bacteria, viruses, or parasites – that then invade and multiply within the body. As Iowa Health & Human Services explains, the organisms either multiply in the intestinal lining or release toxins after colonising the gut.

Because the pathogens need time to multiply inside the host before symptoms appear, foodborne infections typically have a longer incubation period – usually measured in days rather than hours. The host commonly experiences fever, nausea, vomiting, abdominal cramps, and diarrhea. Well-known examples of infection-causing pathogens include Salmonella, E. coli, Listeria monocytogenes, and Campylobacter jejuni.

Foodborne intoxications 🔗

In contrast, a foodborne intoxication happens when a person consumes food that already contains toxins produced by microorganisms. The bacteria may have grown and produced these toxins in the food before it was eaten – the live bacteria themselves may or may not still be present at the time of consumption.

Because the preformed toxin acts on the body directly, intoxications typically cause illness much more quickly – within minutes to hours. Vomiting and diarrhea are the most common symptoms. Classic examples include Staphylococcus aureus food poisoning (where toxins cause vomiting within 30 minutes to 6 hours) and Clostridium botulinum intoxication, where a potent neurotoxin attacks the nervous system.

Major foodborne pathogens you should know 🔗

While hundreds of organisms can cause foodborne illness, a handful of pathogens are responsible for the vast majority of cases worldwide. Here are the most significant ones.

Salmonella 🔗

Salmonella is one of the most frequently reported causes of foodborne illness globally. The Salmonella family contains over 2,300 serotypes, but Salmonella enteritidis and Salmonella typhimurium are the most common in many countries. These bacteria live in the intestinal tracts of animals and humans and are most commonly transmitted through eggs, poultry, raw milk, and undercooked meat.

Symptoms of salmonellosis include watery diarrhea (sometimes bloody), stomach cramps, headache, nausea, vomiting, and fever. These typically appear 6 hours to 6 days after ingesting the bacteria. While most people recover within a week, severe cases may require hospitalisation, especially among children, the elderly, and immunocompromised individuals.

Escherichia coli (E. coli) 🔗

E. coli is a large group of bacteria that naturally inhabits human and animal intestines. Most strains are harmless, but certain pathogenic types – especially Shiga toxin-producing E. coli (STEC) like O157:H7 – can cause severe illness. Contaminated food (undercooked ground beef, unpasteurised milk, raw leafy vegetables) and water are common sources of infection.

Symptoms include severe abdominal cramps and diarrhea that often becomes bloody. In some cases, particularly among young children and the elderly, STEC infections can progress to Hemolytic Uremic Syndrome (HUS), a serious condition that causes kidney failure. According to research published in the International Journal of Environmental Research and Public Health, leafy green vegetables and beef products are the food categories most frequently attributed to E. coli O157 outbreaks.

Listeria monocytogenes 🔗

Listeria monocytogenes causes an infection called listeriosis, which is particularly dangerous for pregnant women, newborns, older adults, and immunocompromised individuals. What makes Listeria uniquely concerning is its ability to grow at refrigeration temperatures – unlike most bacteria that require warmer conditions to multiply.

The bacterium is commonly found in unpasteurised dairy products, ready-to-eat deli meats, smoked seafood, and raw vegetables contaminated by soil or water. The WHO notes that Listeria infections can cause miscarriage in pregnant women or death in newborns. While listeriosis is relatively rare compared to salmonellosis, its fatality rate is significantly higher.

Clostridium botulinum 🔗

Clostridium botulinum is a spore-forming, anaerobic bacterium (it thrives in low-oxygen environments) that produces one of the most potent neurotoxins known to science. The disease it causes – botulism – is rare but extremely serious. The USDA Food Safety and Inspection Service (FSIS) describes botulism as a life-threatening disease caused by ingesting this neurotoxin.

The toxin attacks the nervous system, causing symptoms such as difficulty swallowing, double vision, muscle weakness, and in severe cases, respiratory failure and paralysis. Symptoms usually appear within 18 to 36 hours of consuming contaminated food. Improperly home-canned foods, vacuum-packed products, and foods stored in oil are commonly implicated. The bacterium cannot grow below a pH of 4.6, which is why acidic foods like pickles and most fruits are generally safe from botulism risk.

Staphylococcus aureus 🔗

Staphylococcus aureus is a classic example of a toxin-producing bacterium that causes foodborne intoxication rather than infection. The bacteria are often transferred to food through improper handling by food workers who carry the organism on their skin or in their nasal passages. Once in the food, S. aureus can produce heat-stable enterotoxins that are not destroyed even by reheating.

Symptoms – mainly severe nausea, vomiting, and abdominal cramps – appear rapidly, often within 30 minutes to 6 hours of eating the contaminated food. Recovery usually happens within 24 hours. Foods most commonly involved include meats, salads, cream-filled pastries, and dairy products left at room temperature for too long.

Other notable pathogens 🔗

Beyond these major players, several other organisms are significant contributors to foodborne disease. Campylobacter jejuni is one of the most common bacterial causes of foodborne illness and is typically transmitted through raw or undercooked poultry and unpasteurised milk. Clostridium perfringens causes illness when large numbers of its vegetative cells are consumed – it is frequently associated with improperly stored cooked meats and gravies. Viruses like Norovirus and Hepatitis A also contribute substantially to the global foodborne disease burden, often spread through contaminated water or food handled by infected workers.

How does food become contaminated? 🔗

Food can become contaminated at any point in the supply chain – from the farm to the table. Understanding these critical points helps in designing effective prevention strategies.

At the production level, fruits and vegetables can be contaminated through polluted irrigation water or soil. Animals may carry pathogens in their intestines, and during slaughter, these organisms can transfer to the meat. During processing, inadequate heat treatment, poor sanitation, or equipment failure can introduce or fail to eliminate pathogens. During distribution and retail, breaks in the cold chain (keeping food at safe temperatures during transport and storage) allow microbial growth.

However, a large proportion of foodborne illness originates in the final step – food preparation at home or in food service establishments. WHO data show that a small number of recurring errors in food handling are responsible for most foodborne disease episodes globally. These include preparing food hours before consumption and storing it at unsafe temperatures, insufficient cooking, cross-contamination between raw and cooked foods, and poor personal hygiene among food handlers.

Prevention: how to keep foodborne diseases at bay 🔗

The good news is that most foodborne illnesses are entirely preventable. Prevention relies on controlling the conditions that allow pathogens to contaminate, survive, and multiply in food. The approach can be summarised in four core steps promoted by FoodSafety.gov: Clean, Separate, Cook, and Chill.

Clean: wash hands and surfaces often 🔗

Thorough handwashing with soap and warm water for at least 20 seconds is the single most effective way to prevent the spread of foodborne pathogens. Hands should be washed before, during, and after preparing food – and always after handling raw meat, poultry, seafood, or eggs. Cutting boards, utensils, and countertops should be washed with hot, soapy water after each use. Fresh fruits and vegetables should be rinsed under running water before eating or cooking.

Separate: prevent cross-contamination 🔗

Raw meat, poultry, seafood, and eggs should be kept separate from ready-to-eat foods at every stage – in the shopping cart, in the refrigerator, and on the kitchen counter. Using separate cutting boards for raw meat and fresh produce is a simple but powerful preventive step. Cross-contamination is one of the leading causes of foodborne illness in home kitchens, and even a tiny amount of raw meat juice on a cutting board can transfer enough bacteria to cause illness.

Cook: reach safe internal temperatures 🔗

Thorough cooking kills most foodborne pathogens. The CDC recommends using a food thermometer to verify that food has reached a safe internal temperature. For instance, whole cuts of beef, pork, and lamb should reach 145°F (63°C) with a three-minute rest time, ground meats should reach 160°F (71°C), and all poultry should reach 165°F (74°C). When reheating leftovers, they should be heated to at least 165°F (74°C). Colour and texture alone are not reliable indicators of safety.

Chill: refrigerate promptly 🔗

Bacteria that cause food poisoning multiply most rapidly between 40°F (4°C) and 140°F (60°C) – this range is known as the danger zone. Perishable foods should never be left at room temperature for more than two hours (or one hour if the ambient temperature exceeds 90°F/32°C). Refrigerators should be set at 40°F (4°C) or below and freezers at 0°F (-18°C) or below. Large batches of cooked food should be divided into shallow containers so they cool quickly and uniformly in the refrigerator.

Beyond the kitchen: systemic prevention 🔗

Prevention is not just an individual responsibility. At the systemic level, food safety depends on robust regulation, inspection, and surveillance across the entire food chain. Governments play a critical role through enforcing standards for food production, processing, and distribution. The WHO’s Global Strategy for Food Safety (2022-2030) emphasises a One Health approach – recognising that human health, animal health, and environmental factors are all interconnected in the food safety ecosystem. Effective surveillance systems, rapid outbreak response, and consumer education are all essential pillars of a comprehensive food safety framework.

Why foodborne diseases matter beyond health 🔗

The impact of foodborne diseases extends far beyond individual sickness. Children under five years of age bear a disproportionate burden – they account for approximately 40% of global foodborne disease cases, with an estimated 125,000 deaths annually. The economic toll is also massive. The World Bank has estimated that low- and middle-income countries lose about $110 billion annually in productivity and medical costs due to unsafe food.

For developing countries in particular, foodborne diseases create a vicious cycle: illness leads to lost workdays, reduced agricultural productivity, increased healthcare expenditure, and lower economic growth – all of which further weaken the capacity to invest in food safety infrastructure. Even in wealthier nations, major outbreaks can damage consumer confidence, disrupt trade, and cost food companies millions in recalls and lawsuits.

A simple framework to remember 🔗

When it comes to keeping food safe, a straightforward mental model helps. Keep it clean – wash your hands, surfaces, and produce. Keep it separate – don’t let raw and ready-to-eat foods mix. Keep it hot – cook food to the right temperature and reheat leftovers thoroughly. Keep it cold – refrigerate promptly and store at safe temperatures. These four principles, consistently applied, can prevent the vast majority of foodborne illnesses.

What do you think? How confident are you in your current food handling habits at home – are there areas where you might be unknowingly putting yourself at risk? And considering that a significant share of foodborne illnesses originate in home kitchens, should food safety education be a mandatory part of school curricula?

References

1. https://www.who.int/news-room/fact-sheets/detail/food-safety
2. https://www.cdc.gov/food-safety/about/index.html
3. https://hhs.iowa.gov/epi-manual-guide-surveillance-investigation-and-reporting/foodborne-outbreak-investigation/appendix
4. https://www.fsis.usda.gov/food-safety/foodborne-illness-and-disease
5. https://pmc.ncbi.nlm.nih.gov/articles/PMC6604998/
6. https://www.fsis.usda.gov/food-safety/foodborne-illness-and-disease/illnesses-and-pathogens/botulism
7. https://www.health.state.mn.us/diseases/foodborne/basics.html
8. https://www.paho.org/en/health-emergencies/who-golden-rules-safe-food-preparation
9. https://www.foodsafety.gov/keep-food-safe/4-steps-to-food-safety
10. https://www.cdc.gov/food-safety/prevention/index.html