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Shigella

While the food we eat in Canada is generally very safe, sometimes it may carry bacteria that can make us sick, like Shigella.

What is Shigella?

Shigella bacteria are found naturally only in the intestines of humans and high primates, mostly in capture (zoos). They are usually transferred to other people, food or water when people do not wash their hands after using the toilet and then touch something or someone else.

People who are infected with Shigella can become ill with shigellosis, an acute intestinal illness. Like other foodborne illnesses, the symptoms of shigellosis can feel like stomach flu, but they can also develop into serious illness with long-lasting effects.

How do people get sick?

Shigellosis, the infection caused by Shigella, can be transmitted through person-to-person contact, poor-quality drinking water, contaminated surfaces or contaminated food. Shigella can also be transferred by flies, which breed in contaminated feces (stool), then contaminate food and surfaces. People can be carriers of Shigella bacteria without knowing it, then spread the bacteria to food, surfaces or other people.

Did you know?

Intestinal illness can be caused by viruses, bacteria or parasites, and usually involves vomiting and diarrhea. People often call it the flu, though it is in no way related to the influenza virus, which causes respiratory illness.

Outbreaks of shigellosis are more common in places where hygiene practices are poor, and under conditions of crowding, like jails, daycare centres, and refugee camps.

Shigella is not naturally present on foods. Food is most often contaminated with Shigella from water polluted by human sewage. Food can also become contaminated if it is handled by a person infected with Shigella or by cross-contamination because of unsanitary food handling practices.

Foods that can become contaminated with Shigella bacteria because of unsafe handling can include:  

  • raw oysters and shellfish harvested from contaminated waters
  • vegetables harvested from fields contaminated with sewage
  • salads (pasta, potato, shrimp, tuna, chicken, turkey, macaroni, fruit, lettuce, vegetable)
  • water contaminated with sewage
  • chopped turkey
  • rice balls
  • beans
  • pudding
  • deli meats
  • unpasteurized milk

You can also be exposed to Shigella bacteria (or spread it) by:

  • not washing your hands with soap after using the bathroom
  • not washing your hands with soap before handling food
  • direct person-to-person contact, including contact with hands that were not washed properly after using the bathroom
  • bathing in contaminated waters

What are the symptoms and treatment?

Fast fact

Shigellosis is most often spread from person-to-person. About 20 per cent of shigellosis infections come directly from contaminated food and water.

People with shigellosis can experience a wide range of symptoms. Some do not get sick at all, though they can still spread the infection to others. Others feel as though they have a bad case of stomach flu. A rare few become seriously ill and must be hospitalized.

Most people with shigellosis develop the following symptoms one to three days after being infected with Shigella bacteria (though symptoms can appear as late as seven days after infection):

  • diarrhea (watery and often bloody)
  • fever
  • nausea
  • vomiting
  • abdominal pains
  • stomach cramps

The illness usually lasts between five and seven days, and most people recover fully, though it may take several weeks to months before bowel habits return to normal. As with any disease causing diarrhea or vomiting, people infected should drink plenty of liquids to replace lost body fluids and prevent dehydration. Although anyone can get shigellosis, pregnant women, people with weakened immune systems, young children and older adults are most at risk for developing serious complications like septicemia (an infection of the bloodstream).

While long-term consequences are rare, a small number of people infected with Shigella flexneri may develop Reiter's syndrome, a condition that develops in response to an infection in another part of the body and can lead to chronic arthritis.

How do I avoid getting sick?

Foods contaminated with Shigella look, smell and taste normal. The good news is, Shigella and many other harmful bacteria can be killed by cooking and preparing (ready-to-eat) food properly.

These tips will help protect you and your family from Shigella:

  • Always wash your hands for 20 seconds with soap after using the bathroom.
  • Wash your hands well with soap before handling any food. Be sure to wash your hands, cutting boards, counters, knives and other utensils after preparing raw foods. This will avoid cross contamination.
  • Cook food to a safe internal temperature using a digital thermometer.
  • Buy shellfish from reputable suppliers.
  • Cook shellfish thoroughly before eating, especially oysters.
  • Drink water from a safe (treated or boiled) water supply.
  • Eat and drink only pasteurized juice, cider, milk and milk products. Mother's milk is the safest food for infants.
  • When travelling, in particular in developing countries, drink water from a safe (treated or boiled) source. Eat only cooked hot food. Eat only fruit that can be peeled.
  • Wash raw fruits and vegetables thoroughly with clean, safe running water before you prepare and eat them. Use a brush to scrub produce with firm or rough surfaces, like oranges, cantaloupes, potatoes and carrots.
  • If you have been diagnosed with shigellosis or any other gastrointestinal illness, do not prepare food or pour water for other people.

Also, these safe food practices will reduce your risk of contracting shigellosis and other foodborne illnesses.

What does the Government do to protect me?

In Canada, several government organizations work together every day to keep your food safe:

  • Health Canada makes food safety standards and policies to help minimize the risk of foodborne illnesses.
  • The Canadian Food Inspection Agency (CFIA) enforces these policies and standards and carries out inspections to make sure the food industry meets its food safety responsibilities. The CFIA works with Health Canada to make sure that foodborne illness is detected early and warnings go out to the public quickly.
  • The Public Health Agency of Canada studies the incidence and causes of diseases in Canada, conducts outbreak surveillance, and coordinates outbreak response.

The Government of Canada works very hard to protect your health and safety:

  • We are carrying out a five-year Food and Consumer Safety Action Plan, to strengthen and modernize Canada's safety system and make sure you can have confidence in the quality and safety of the food, health and consumer products you buy.
  • We are investing $75 million more in Canada's food safety system (on top of the $113 million committed in 2008) to hire more inspectors, update lab technology, and improve communication with Canadians.
  • We support and participate in public awareness campaigns about safe food practices, like the Canadian Partnership for Consumer Food Safety Education's Be Food Safe program, which encourages Canadian consumers to think of food safety at every step of the food handling process, from shopping for groceries to re-heating leftovers.
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