Canadian health officials say 12 deaths have been linked to a listeriosis outbreak from a Maple Leaf Foods plant in North York, Ont, leading to an expanded recall of at least 220 meat products, and raising concerns about public health.

Click on this link for a complete list of affected Maple Leaf meats.

Here are some answers to frequently asked questions about about Listeriosis:

What is Listeriosis?

Listeriosis, a serious infection caused by eating food contaminated with the bacterium Listeria monocytogenes, has recently been recognized as an important public health problem in the United States and Canada.

The disease affects primarily persons of advanced age, pregnant women, newborns, and adults with weakened immune systems. However, persons without these risk factors can also rarely be affected. The risk may be reduced by following a few simple recommendations.

What are the symptoms of the disease?

Fortuantely, many people who consume the bacteria will not get sick --but if you do get ill, the symptoms usually come on about 3 weeks after eating the contaminated food--they include:

A person with listeriosis has a feeling like they have the flu with fever, muscle aches, gastrointestinal symptoms such as nausea and diarrhea. It can be deadly if the bacteria infects the lining of the brain causing headache, stiff neck and confusion.

How great is the risk of Listeriosis?

Some people are more at risk than others. People who are most at risk are those with weakened immune systems, the elderly and pregnant women .

In fact pregnant women are about 20 times more likely to get sick than others.

This is why we tell pregnant women to avoid eating soft cheeses and deli meats during pregnancy because this infection can cause miscarriage, stillbirths and can even be fatal to the baby.

How does Listeria get into food?

Listeria monocytogenes is found in soil and water. Vegetables can become contaminated from the soil or from manure used as fertilizer.

Animals can carry the bacterium without appearing ill and can contaminate foods of animal origin such as meats and dairy products.

Can Listeriosis be treated?

When infection occurs during pregnancy, antibiotics given promptly to the pregnant woman can often prevent infection of the fetus or newborn.

Babies with listeriosis receive the same antibiotics as adults, although a combination of antibiotics is often used until physicians are certain of the diagnosis.

How do you know if you have Listeriosis?

There is no routine screening test for listeriosis during pregnancy, as there is for rubella and some other congenital infections.

If you have symptoms such as fever or stiff neck, consult your doctor. A blood or spinal fluid test (to cultivate the bacteria) will show if you have listeriosis. During pregnancy, a blood test is the most reliable way to find out if your symptoms are due to listeriosis.

For more information, check the Atlanta Centre for Disease Control website.