A recent recall of deli meat across the United States is raising questions about the potentially harmful bacteria listeria.

Roast beef and ham that was distributed to Walmart delis nationwide was recalled because it might be tainted with listeria. 

No illnesses have been reported from the 380,000 pounds of meat.  It was made by Tyson Foods unit Zemco Industries in Buffalo.

A spokesman for the company says he believes the affected products have already been consumed.

Onondaga County Health Commissioner Dr. Cynthia Morrow says many people don't have any symptoms after coming in contact with listeria. 

In fact, there has only been one reported case in the county so far this year.  In 2008 and 2009, there were no cases reported. 

Dr. Morrow says the bacteria can travel through many products, including unpasteurized milk, cheese made with unpasteurized milk, deli meats, and even fruits and vegetables.

For most people, it's harmless, but for pregnant women, people who have compromised immune systems, and the elderly, it can cause illness or even death.

Dr. Morrow says they should take precautions.

"We still recommend the same things that we do for all food borne illnesses," says Morrow.  "Make sure you thoroughly wash your hands, watch out for cross contamination, and cook your food appropriately."

She says if pregnant women do want to eat deli meat, they should cook it. 

If someone comes in contact with listeria, symptoms could take 3-70 days to develop. 

Click here for more on the recall.  Also, more from Tyson, Listeria, Onondaga County Health Department and Walmart.