Health Canada estimates there are about four million cases of food-borne illness in the country every year, and the summer season creates ideal conditions for many of these cases.Illustration by Matthew Billington
Ask a Doctor is a series of physician-authored columns offering insights and advice on common health topics. It is not a substitute for seeking medical care.
Every summer, emergency departments see a familiar uptick in patients with “food poisoning.” In many cases, people don’t realize what food was the cause until long after the fact, since the incubation period for food-borne illness can stretch hours, sometimes even days, making it easy to blame whatever you ate most recently rather than what actually made you sick.
Health Canada estimates there are about four million cases of food-borne illness in Canada every year. The summer season creates ideal conditions for many of these cases: Food spends more time outside the refrigerator, and bacteria thrive in warm temperatures. In addition, many of our favourite warm-weather dishes are particularly vulnerable.
If you’re cooking or eating outside this summer, whether at a backyard barbecue or while camping or picnicking, here are some common culprits to be aware of — and how you can avoid them.
Some causes of food poisoning
Bacillus cereus is a spore-forming bacteria found in soil that easily contaminates grains and vegetables. Unlike salmonella or E. coli, cooking or reheating won’t protect you, as B. cereus produces spores that survive heat. It’s the toxins those spores generate at room temperature that make you sick, not the actual bacteria.
Symptoms can come in two forms: nausea and vomiting within a few hours, or watery diarrhea and cramping six to 15 hours later.
The fix is simple: Get cooked food, including rice and pasta, into the fridge promptly and don’t leave them sitting out while you set up everything else.
Staphylococcus aureus food poisoning is often blamed on mayonnaise, but that’s not quite right. Commercial mayo is acidified and relatively resistant to bacterial growth. The real risk in popular summer dishes such as potato salad comes from the low-acid ingredients (potatoes, pasta, hard-boiled eggs), which offset the acidity and create conditions where bacteria thrive.
S. aureus can also spread through the people handling food, since the bacteria lives on skin, particularly around the nose and eyes, and gets into food when people touch their face and then handle dishes without washing their hands.
Illness typically begins abruptly within four hours, with nausea and vomiting.
The toxins are heat-stable, meaning reheating won’t save contaminated food.
Salmonella and E. coli are the risks hiding on your grill. Undercooked poultry is a common source of salmonella, while harmful strains of E. coli are associated with undercooked ground beef. One of the most common mistakes at barbecues is using the same plate or utensils for raw and cooked meat. Cross-contamination can make people sick even when the food was cooked properly. Use different utensils and plates for raw and cooked meat, or wash them in between. It’s also important to use a meat thermometer rather than relying on colour to determine doneness.
These infections often produce diarrhea, abdominal pain and fever, but symptoms may not appear for several days after exposure.
Vibrio bacteria occur naturally in marine environments and multiply as water temperatures rise, making raw oysters at a summer gathering a particular risk. Popular pairings with such items as lemon juice, hot sauce and alcohol don’t kill Vibrio; only thorough cooking does.
Symptoms appear within 24 hours and include diarrhea, cramps, nausea, vomiting and headaches.
For most healthy people, vibriosis is unpleasant but resolves on its own without specific treatment. However, in people with weakened immune systems or chronic liver disease, it can become a severe, life-threatening bloodstream infection.
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Managing food poisoning at home
Thankfully, most food-borne illnesses resolve on their own. The priorities are rest and hydration since vomiting and diarrhea can cause fluid loss quickly. Frequent small sips of water, oral rehydration solutions, broth or electrolyte-containing fluids are often better tolerated than attempting to drink large amounts at once.
Once nausea improves, bland foods such as toast, crackers, rice and bananas can help ease the transition back to normal eating, but I typically recommend eating whatever there is an appetite for.
Avoid anti-diarrheal medications such as loperamide unless directed by a physician. In some situations, this can actually worsen illness.
When to seek care
Most people recover within a few days without medical intervention. However, certain symptoms warrant prompt medical attention, including:
- Signs of significant dehydration, such as no urination for eight or more hours, extreme dizziness, dry mouth or confusion
- Blood in stool or vomit, high fever, or severe abdominal pain
- Symptoms lasting more than three to five days without improvement
- Any symptoms in an infant under three months, an older adult, a pregnant person or someone who is immunocompromised
- If you’re unsure, call 811 for health advice before heading to the emergency department (ED)
How to host a safer barbecue
The best treatment is always prevention.
Keep cold food cold. Food enters the danger zone between 4 C and 60 C, where bacteria multiply rapidly. Protein salads, dairy, eggs and cooked grains should stay refrigerated until just before serving. Use coolers and ice packs when transporting foods and nestle dishes in bowls of ice if you’re eating outside.
Follow the two-hour rule. Perishable food should not be left at room temperature for more than two hours; if it is, discard it. On a hot day, that two-hour window is even shorter.
Separate raw from ready-to-eat. Use different cutting boards, plates and utensils for raw meat and everything else. Wash hands after handling raw meat or seafood before touching anything else.
When in doubt, throw it out. No dish is worth a night of belly pain in the ED.
Dr. Shazma Mithani is an emergency physician working with adult and pediatric patients in Edmonton. She is actively involved with the Canadian Medical Association and the Alberta Medical Association, and is also co-host of the Doc Talk Podcast.