Small numbers with a big impact. This is how scientific experts describe the situation with foodborne illness caused by Listeria monocytogenes. In terms of sheer numbers, this bacteria is a small player. Unlike Salmonella, E. coli or other pathogens responsible for large numbers of foodborne illness cases every year, Listeria is lower on the culprit list. It causes about 2,500 cases of foodborne illness in the US annually.

The shocking fact, however, is that 20% of its victims die from the illness — 500 consumers per year. Certainly, we focus special attention on the elderly and those with suppressed immune systems when we plan food protection efforts. Listeria, though, has its greatest impact among pregnant women.

According to the Centers for Disease Control (CDC), compared with most others, pregnant women are at 20 times the risk of contracting Listeriosis, the illness caused by the Listeria bacteria. Many serious cases in fact involve pregnant women. In addition, the results of the illness are ravaging. Listeriosis often results in miscarriage or stillbirth.

Another group at exceptionally high risk for the illness is individuals suffering from AIDS. These sufferers are 300 times more likely to become ill with Listeriosis. Surprisingly, children seem less susceptible to this bacteria than to many other foodborne pathogens.

CDC officials say that probably many children and healthy adults contract Listeriosis and experience symptoms similar to a mild flu, which may never actually be diagnosed as a foodborne illness.

More Facts

Where does this bacteria come from? It occurs in soil. This means it can contaminate plants (crops). Furthermore, animals can carry the bacteria without appearing ill. Thus, it gets into meat and milk. Symptoms of Listeriosis may include:

Nausea and vomiting
Stiff neck (which may become meningitis)
Headache and muscles aches
Loss of balance, convulsions
Delirium, coma

How long does it take from consumption until symptoms occur? This is variable. Symptoms may start as soon as two days. But health officials are finding cases that crop up as long as four or five weeks after consumption. A slow-moving illness like this poses special challenges for health officials. By the time they begin to pinpoint a suspicious food, it may have been eaten by large numbers of consumers.

This happened with a 10-state outbreak a few years ago. Only by polling Listeriosis victims about everything they had eaten over the past month did scientists track down a source from a processed meat manufacturer. Primarily, the problem stemmed from hot dogs. Once this was discovered, the manufacturer initiated a recall.

Physicians can diagnose Listeriosis by performing a test of blood or spinal fluid. Once diagnosed, the bacterial illness responds to antibiotics. Now, what foods are we talking about? Along with hot dogs, foods most often cited in Listeriosis cases include:

cold cuts, such as bologna or salami
smoked seafood, such as lox, nova-style salmon, kippered fish
unpasteurized cheeses, such as Brie, camembert, or feta
meat spreads and pates (unless canned or shelf-stable)

Prevention

Awareness of the risks is the best step towards prevention. In the case of Listeria, a little extra control is necessary. This is because Listeria bacteria can grow under refrigeration. Heat does destroy Listeria. So, once cooked to recommended time and temperature standards, foods become safe. As it happens, some Listeria-prone foods are usually served cold, without undergoing cooking. A bologna sandwich, a chilled pate, or a salad containing Brie cheese are all examples. All of these pose a Listeria hazard.

To control the hazard, you can take a number of steps:

Carefully monitor date codes for all refrigerated items
Practice FIFO (first in, first out) rotation practices
Discard outdated deli products (Remember: The longer a Listeria-contaminated product sits in your refrigerator, the more bacteria will grow.)
Make sure your refrigerators and cold storage units hold food at or below 41°F (A few degrees higher can speed up Listeria growth dramatically.)
Keep the refrigerator clean
Avoid cross contamination in storage, production, and service
Insist on proper handwashing, which can control the spread of the bacteria
Avoid purchasing or using unpasteurized dairy products or soft, fresh cheeses (Pasteurized dairy products, such as yogurt, cottage cheese, cream cheese, cheddar cheese, and others are OK.)
Avoid purchasing or using smoked seafood or pates (canned or shelf-stable products are OK.)
Establish and control endpoint cooking times and temperatures for hot dogs and other susceptible products
Re-heat leftovers according to FDA guidelines

More to Come

Today, a government action plan is underway to further control Listeriosis from several angles. The Listeria Action Plan, initiated by Health and Human Services/USDA last year, began with an assessment of the risks. In their assessment, officials categorize Listeriosis as "a moderately rare though severe disease."

They note that consumer exposure to the bacteria is influenced by how much Listeria-contaminated food a person eats, how Listeria bacteria grow after food processing, and how consumers and foodservice operations store and manage Listeria-prone foods.

Today, the government is looking to provide guidance to the food processing and distribution industries, education for consumers, and ongoing surveillance to better handle the hazards and prevent this illness.

By Sue Grossbauer