Listeria cases have increased due to foodborne illnesses.

There have been three prominent Listeria outbreaks recorded in the United States this year connected to prepared foods, including pasta meals such as chicken fettuccine Alfredo.

About 172 people die from the disease every year, making it the third most common foodborne infection in the United States, according to the Centers for Disease Control and Prevention. Hospitalization is necessary for most patients and the disease has a case-fatality rate of about 20%, which is far greater than other foodborne illnesses.

What states have reported listeria cases?

The states that are affected by listeria include: California, Florida, Illinois, Indiana, Louisiana, Michigan, Minnesota, Missouri, Nevada, North Carolina, Ohio, South Carolina, Texas, Utah and Virginia, according to the CDC.

The impacted patients are between the ages of 4 and 92. Since some people recover from listeriosis without medical attention and never get tested, the CDC estimates that the actual number of people ill is probably substantially higher than reported, and that the outbreak may not be restricted to the states shown below.

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What is listeria monocytogenes? Does listeria go away on its own?

Listeria monocytogenes is a bacteria that can cause listeriosis, a foodborne illness, according to the Food and Drug Administration. As of Sept. 30, there have been a total of four deaths, 19 hospitalizations and 20 cases across 15 states have become ill due to the disease, according to the CDC.

While healthy people exposed to the bacteria might experience only minor symptoms ‒ or none at all ‒ pregnant women, newborns, elderly people and those with compromised immune systems are more susceptible to listeriosis.

Certain foods, such as processed deli meats, hot dogs, pasteurized and unpasteurized dairy, soft cheeses, raw or smoked fish, and raw or processed vegetables, have a greater chance of being contaminated with listeria, according to the FDA and Mayo Clinic.

How does listeria spread?

Listeria bacteria can withstand freezing and refrigeration. If you are more susceptible to serious infections, be cautious of what you eat. Try to steer clear of items that are more likely to contain the bacteria.

What are the symptoms of listeria? How long does it take to set in?

About 1 in 6 people with severe listeria infection die each year, according to the CDC. Severe infections can result in miscarriages, stillbirths, and early delivery in pregnant women, and potentially fatal infections for the baby due to spread outside of the gastrointestinal system.

Tips to help prevent foodborne illness at home

Here are some simple steps to prevent listeria and other foodborne illnesses from entering your home, according to the U.S. Department of Agriculture:

Keep it clean: Your hands and other surfaces are among the many places in which germs can thrive. Always use soap and warm water to wash your hands for at least 20 seconds both before and after cooking and eating.

Keep food separate: Foods that are ready to eat, such as fruits and vegetables, should be kept away from raw meats, poultry, shellfish and eggs. Use separate cutting boards and containers to avoid cross-contamination between raw meats and fruits and vegetables. This will prevent the spread of bacteria.

Even cooking: Make sure food is cooked to the right internal temperature by using a food thermometer. If you're using a microwave, make sure your food is thoroughly heated through. To facilitate even heating, let food rest for a few minutes after cooking.

•Keep it cool: Store leftovers in the refrigerator as soon as possible after serving. Food left between 40°F and 140°F can quickly grow bacteria. After serving, perishable items should be refrigerated within two hours.

SOURCE: Centers for Disease Control and Prevention, Mayo Clinic, University of Minnesota, State of North Carolina Division of Public Health, Department of Agriculture and the Food and Drug Administration

This article originally appeared on USA TODAY: What is listeria? When do symptoms start? We explain the foodborne illness.

Reporting by Janet Loehrke, USA TODAY / USA TODAY

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