We've all been there - you have lunch with your coworkers at a nearby greasy spoon, and later that evening, something doesn't feel quite right. You start to feel queasy, like your insides are having second thoughts about that ham sandwich you enjoyed so much. Suddenly, you have to make a dash to the bathroom. The culprit? Food poisoning, an affliction spread through the consumption of contaminated food or beverages.

According to the Public Health Agency of Canada, 4 million people are stricken with food poisoning every year in Canada. While most people fully recover from their bout of food poisoning, 2% to 3% of cases lead to more serious chronic conditions such as hemolytic uremic syndrome (HUS) and kidney failure. When poisonous microbes or toxins (such as those found in poisonous mushrooms) are swallowed, they move through the gastrointestinal tract and attach to the intestinal walls and begin to multiply. Symptoms vary and typically include nausea, vomiting, abdominal cramps, and diarrhea.

Diagnosing a food borne infection requires laboratory tests to identify the guilty organism. Many people are victims of food poisoning and don't realize it. According to the Centers for Disease Control in the United States, there are actually about 38 cases of salmonellosis for every case that is diagnosed and reported.

Treatment of food poisoning depends on the symptoms. People suffering from vomiting or diarrhea are at risk of becoming dehydrated, so treatment includes restoring lost fluids and electrolytes. (If diarrhea is severe, an oral rehydration solution may be needed.) Medications can help relieve diarrhea, but should be avoided if you have a high fever or blood in the stools.

Many cases of diarrhea are caused by viruses and will get better on their own within 1 to 2 days without antibiotics. If you have diarrhea that lasts longer than 2 days or comes with a high fever (temperature over 38.5°C), bloody or black stools, passing more than 6 bowel movements in 1 day, severe abdominal cramps, prolonged vomiting (especially if you can't keep liquids down), dry mouth or throat, dizziness, or decreased urination, seek medical help immediately. Wash your hands thoroughly and often, especially after going to the bathroom and before eating, to prevent infecting others.

Let's look at some of the most common infection-causing microbes.

E. coli

E. coli and its toxins have been found in undercooked hamburger, lettuce, alfalfa sprouts, unpasteurized milk, apple juice, and apple cider. You can also pick up E. coli through contact with an infected person or swimming in water with traces of human feces.

Symptoms usually begin 2 to 5 days after ingesting contaminated foods or liquids, and may last for a week before you recover completely, typically without treatment (antibiotics won't usually help, and antidiarrheal medications aren't recommended).

To prevent illness, wash your hands after using the bathroom or changing diapers. Thoroughly cook ground beef (the internal temperature should be 71°C), and keep raw meat away from other foods. Don't drink unpasteurized milk and juice, and wash fresh fruits and vegetables before eating.


Salmonella bacteria is usually passed to humans when they eat foods contaminated with animal feces. It is found on beef, poultry, milk, and eggs, but any food can be contaminated. Pets, especially reptiles, can carry salmonella.

Salmonella causes an infection known as salmonellosis. Most people develop diarrhea, fever, and abdominal cramps or bloody stools 12 to 72 hours after infection, and the symptoms last for 4 to 7 days. Most people recover without treatment, but some must be hospitalized and treated with antibiotics.

To avoid infection, don't eat raw or undercooked eggs, meat, or poultry, and don't drink unpasteurized milk. (Watch out for raw eggs in homemade salad dressings, mayonnaise, cookie dough, and frosting.) Thoroughly cook poultry and meat and avoid unpasteurized dairy products. Wash fruits and vegetables carefully. Keep uncooked meats away from other foods and avoid contaminating through the use of utensils, counters, cutting boards, and your hands while preparing food. Wash utensils, counters, and cutting boards with soap and hot water after preparing uncooked animal products. Wash your hands after handling animal feces or playing with reptiles.


Campylobacter bacteria causes campylobacteriosis, a disease that causes diarrhea, cramping, abdominal pain, nausea or vomiting, and fever 2 to 5 days after infection. People usually recover without treatment within 1 week, but they should drink plenty of fluids until diarrhea resolves. In severe cases, antibiotics may be used.

Campylobacteriosis is usually linked to handling raw poultry or eating undercooked poultry. To avoid illness, cook poultry thoroughly - it shouldn't be pink inside and juices should be clear. Wash your hands before and after handling animal products. Use separate cutting boards for animal products and other foods, and wash utensils, counters, and cutting boards with soap and hot water after preparing raw animal products. Don't drink unpasteurized milk.