Foodborne Illness
Foodborne illness results from eating food contaminated with pathogens such as bacteria (or their toxins), parasites, or viruses. Although most foodborne infections are undiagnosed and unreported, the Public Health Agency of Canada estimates that every year about 1 in 8 people in Canada become ill from pathogens in food. Of these, over 11,500 are hospitalized and 240 die.1
Causes
Most cases of foodborne illness result from food being prepared or stored improperly. When food is cooked and left out at room temperature, bacteria and other microorganisms can quickly multiply. Within two hours, food can become dangerous to eat. There is often no easy way to tell whether it is safe to eat, as most bacteria do not change the colour, texture, smell, or flavour of the food within this time. Refrigerating food slows the growth of bacteria, and freezing might even stop it, but neither method destroys bacteria. When defrosted, they can begin to rapidly grow again. You must thoroughly cook your food to ensure that no bacteria continue to thrive.
Unhygienic preparation can also lead to foodborne diseases. This includes cooking with dirty hands (e.g., after using the toilet, changing diapers, playing with pets, etc.), not cleaning surfaces before and after preparing food, and using the same cooking utensils for raw meat and ready-to-eat foods.
Some types of foodborne illness are also transmissible person-to-person, whether through direct contact or from touching objects that an infected person has touched.
Risk Factors
While anyone who consumes contaminated food is at risk of developing foodborne illness, some people are more likely to both get sick and experience severe symptoms. Those at highest risk include people whose immune systems aren’t working well, including:
- infants and young children
- pregnant women and their growing fetuses
- seniors
- individuals who are immunocompromised (e.g., those who take biologics, high-dose steroids, immunosuppressants, or certain cancer medications, and individuals with HIV)
Diagnosis
Foodborne illness generally doesn’t require a diagnosis. However, for more severe cases, your doctor might ask for a list of what you’ve recently eaten and order laboratory tests. This typically involves analysing a stool sample, and if possible, testing a sample of the suspected food for bacteria and their toxins, viruses, and/or parasites.
Symptoms and Treatment
While different sources of infection can lead to different symptoms, most involve diarrhea and/or vomiting. Because of this, dehydration is always a risk. Symptom onset usually begins within a few hours to a few days after exposure. Fever, abdominal cramping, headache, and feeling generally unwell are also common.
Since most cases of foodborne illness are mild, you can treat them at home with adequate hydration and rest. Focus on drinking plenty of fluids and incorporating electrolytes if you experience vomiting or diarrhea. Sports drinks aren’t a great source of electrolytes, so it is better to use oral rehydration products (e.g., Pedialyte®, Hydralyte®). Eating simple, salty foods, such as salted crackers and broth, can also help your body retain the fluids that you consume.
If you are vomiting too much and therefore not keeping enough liquids in your body to stay hydrated, you might need to go to an urgent care centre or hospital emergency department. Infants and young children are especially at risk for dehydration, so you should monitor them closely for signs of severe dehydration (see below). Hospitals can provide intravenous fluids to improve hydration.
Some types of bacterial foodborne diseases can be treated with antibiotics.
When to Get Help
You need to see a doctor right away if you have any of the following symptoms, with or without gastrointestinal symptoms:
- signs of shock: weak or rapid pulse, shallow breathing, shaking, chills, chest pain, or cold, clammy, pale skin
- signs of severe dehydration: dry mouth, sticky saliva, decreased urine output, dizziness, fatigue, sunken eyes, low blood pressure, sunken soft spot (fontanelle) in infants, and increased heart rate and breathing
- confusion or difficulty reasoning
12 Tips to Prevent Foodborne Illness
- Wash your hands with hot, soapy water before preparing food and after using the bathroom or changing diapers.
- Clean surfaces well before using them to prepare foods.
- Clean surfaces and cooking utensils well after cooking meat to prevent cross-contamination.
- Keep raw meat, poultry, or seafood and their juices away from ready-to-eat foods.
- Cook food to the appropriate temperature (see chart).
- Refrigerate foods within 2 hours after cooking.
- Maintain hot cooked food at 60°C (140°F) or higher if you aren’t refrigerating it right away.
- Set your refrigerator to 4°C (40°F) or lower and your freezer to -17°C (0°F).
- Never defrost food on the kitchen counter. Use the refrigerator, cold running water, or the microwave.
- Never let food marinate at room temperature; always refrigerate it.
- Divide large amounts of leftovers into small, shallow containers for quick cooling in the refrigerator.
- Do not put too much food in your refrigerator. Cool air must circulate to keep food safe.
Safe Temperature Guidelines
Always cook meats to at least these temperatures and use a meat thermometer to be sure!
- 63°C (145°F) for seafood, roasts, steaks, and chops of beef, veal, and lamb
- 71°C (160°F) for pork, ground veal, and ground beef
- 74°C (165°F) for ground poultry or when reheating leftovers
- 82°C (180°F) for whole poultry
Links to Other Disorders
Like with other forms of infection, severe cases of foodborne illness can sometimes cause a variety of chronic diseases. When pathogens make us ill, the body initiates an immune response to fight it off. However, sometimes this can trigger an inappropriate autoimmune response, which means the immune system attacks the body’s own cells. In some people, an autoimmune response leads to a chronic health condition, but they can resolve over time.
Chronic conditions that may be triggered by foodborne pathogens include:
- reactive arthritis
- inflammatory bowel disease
- irritable bowel syndrome
- kidney disease
- gallbladder disease
- Guillain-Barré syndrome
Common Sources of Foodborne Illness1,2,3,
Norovirus (Viral Gastroenteritis)
Time to disease onset: 12-48 hours
Duration of illness: 12-60 hours
Sources: spreads easily from person-to-person, can be passed through any food touched by an infected person or exposed to contaminated water during growth and processing, including raw produce.
Symptoms: nausea, vomiting (more common in children), diarrhea (more common in adults), stomach cramps, abdominal pain, chills, fatigue, mild fever, and headache.
Complications: norovirus outbreaks are most frequent in settings where large groups of people are in small spaces indoors. Common locations, such as nursing homes, daycares, schools, and hospitals, spread the virus quickly to many vulnerable individuals. Norovirus is the most common source of foodborne illness in Canada, with an estimated 1 million cases per year.
Campylobacter jejuni (Campylobacteriosis)
Time to disease onset: 2-5 days
Duration of illness: 3-6 days
Sources: C. jejuni is found in the intestines of several animals. It can get into meat and any water exposed to animal feces. The most common sources include raw or undercooked meat, raw dairy products, raw vegetables (that have been exposed to contaminated water), shellfish, and contaminated drinking water.
Symptoms: watery or bloody diarrhea, abdominal pain, fever, nausea, and vomiting.
Complications: infection with C. jejuni is very common, but it is generally mild. Infants, seniors, and individuals who are immunocompromised are at risk of more severe disease.
E. coli O157:H7
Time to disease onset: 1-8 days
Duration of illness: 5-10 days
Sources: the most common source is undercooked beef, especially ground beef. Raw/unpasteurized dairy products and contaminated raw fruits and vegetables (especially leafy greens and sprouts), as well as juices made from them, are also common sources. You can also get E. coli through exposure to feces from infected people or animals, such as from someone who uses the toilet then prepares food without washing their hands.
Symptoms: severe diarrhea that is often watery and bloody, abdominal pain and cramps, nausea, vomiting, and headache.
Complications: in some people, especially children under 10 years, infection by E. coli O157:H7 can lead to hemolytic uremic syndrome (HUS), a condition that involves kidney damage and can sometimes be fatal. Symptoms of HUS include fever, lethargy, irritability, and pallor. Complications can involve acute renal failure, seizures, heart failure, inflammation of the pancreas, and diabetes. HUS is fatal in 3-5% of cases, but most children recover completely with proper care.
Listeria monocytogenes (Listeriosis)
Time to disease onset: 9-48 hours for mild cases, can be up to 90 days for invasive listeriosis
Duration of illness: varies
Sources: unpasteurized dairy products are a common source, especially soft cheeses, as are refrigerated smoked fish, deli meats, hot dogs, and pâté.
Symptoms: in mild cases (non-invasive listeriosis) they include diarrhea, nausea, vomiting, stomach cramps, muscle aches, headaches, and fever.
Complications: severe cases (invasive listeriosis) can be fatal. The bacteria can reach the nervous system and brain. Symptoms such as confusion, loss of balance, and stiff neck can indicate this, and warrant immediate help from healthcare professionals. This is more common in seniors and immunocompromised people. Pregnant mothers can pass the infection to their fetuses, who are at particular risk. Listeriosis during pregnancy can cause miscarriage or stillbirth, premature birth, or serious illness in babies after birth. If you are pregnant and think you might have listeriosis, contact your healthcare team, even if your symptoms are mild. Antibiotics can treat listeriosis and prevent severe complications.
Salmonella enteriditis (Salmonellosis)
Time to disease onset: 6-72 hours
Duration of illness: 2-7 days
Sources: raw or undercooked eggs are the most well known, but raw meat, dairy, and produce can all be sources. You can also get it through contact with animals, including birds, reptiles, cats, dogs, rodents, and livestock, from a person who is infected, or from contaminated surfaces.
Symptoms: nausea, vomiting, diarrhea, stomach cramps, abdominal pain, chills, fever, and headache.
Complications: most people with salmonellosis experience mild disease. The biggest risk is dehydration, which is most likely to affect vulnerable groups.
Other Sources of Foodborne Illness
There are several other types of foodborne illness that are possible, but not as common. These include bacteria such as Clostridium perfringens, Shigella, and Vibrio; parasites such as Cronobacter and Cyclospora; and viruses such as hepatitis A and E.
One rare, but especially dangerous cause of foodborne illness, is Clostridium botulinum bacteria (botulism). Improperly canned foods (especially vegetables or fruit), smoked or salted fish, oil, jars of garlic in oil, and baked potatoes wrapped in aluminum foil are possible sources. Symptoms include nausea, vomiting, diarrhea, constipation, dry mouth, drooping eyelids, difficulty swallowing, blurred or double vision, unreactive pupils, difficulty speaking, slurred speech, hoarseness, and partial facial paralysis.
The bacteria produce spores that are difficult to destroy with heat and are particularly dangerous for infants. Honey can contain these spores, so it is important to make sure that infants younger than one year old never have any honey. Signs of botulism in infants include vomiting, drooling, irritability, weak cry, constipation, difficulty sucking or feeding, lethargy, loss of head control, and muscle weakness that starts at the head and spreads downwards. Contact your healthcare team immediately if your baby shows these symptoms. There is an antitoxin that can prevent further damage from botulism.
Conclusion
While foodborne illness is common, serious symptoms are generally rare. However, certain populations, including infants, young children, pregnant women, seniors, and individuals who are immunocompromised, are at an increased risk of serious disease. It is important to always follow safe preparation standards, including washing all fruits and vegetables, cooking foods thoroughly, refrigerating foods promptly, and avoiding cross-contamination between raw meat and foods that are eaten uncooked. Vulnerable individuals need to be extra vigilant, wash food thoroughly, and avoid eating raw or undercooked meat, dairy, eggs, and fish. You can also find information on foods that have been recalled due to the presence of microorganisms that can cause foodborne illness through Health Canada’s Recalls and Safety Alerts.5