As U.S. health officials deal with nationwide recalls of Blue Bell ice cream and Sabra Dipping Co. hummus, consumers are getting up to speed on a little known but potentially fatal bacteria, listeria.
Listeria-tainted ice cream is linked to a total of five illnesses and three deaths in Texas and Kansas, the U.S. Centers for Disease Control and Prevention said Thursday.
Also this week, Sabra recalled 30,000 cases of classic hummus, because of listeria-contamination concerns.
"Listeria causes about 1,600 infections a year and about three to four outbreaks a year in the United States," said Dr. Robert Glatter, an emergency physician at Lenox Hill Hospital in New York City.
About 260 deaths occur as a result -- far fewer than the number linked to salmonella, another foodborne illness, the CDC says.
Dr. Brendan Jackson, a medical epidemiologist at the CDC, said that the number of severe cases of listeria is "actually rare."
"If you have eaten a food that has been recalled and you don't have any symptoms there is no need to worry," he said. But if symptoms do develop over the next few weeks, see your doctor, Jackson said.
Glatter agreed that "most people who eat food contaminated by listeria won't become very ill. They can have nausea, vomiting, muscle ache and diarrhea."
However, he added, "there is a more invasive type of illness that can affect people with weakened immune systems, such as those who have HIV, or people with diabetes, heart disease, pregnant women, infants and the frail elderly."
In these people, listeria can cause serious illness, including meningitis and blood poisoning. "It can also result in stillborn infants and miscarriages," he said.
Listeria has been found in unpasteurized dairy products and in ready-to-eat meats, especially hot dogs and deli meats, Glatter said.
The bacteria are usually associated with failure to keep foods cool enough or keeping foods too long. For example, open packages of hot dogs or deli meats shouldn't be kept for more than three to five days, he said.
"If you keep them longer, the risk of harboring bacteria such as listeria increases significantly," Glatter said.
Unlike most other bacteria, listeria can grow and multiply in the refrigerator, the CDC warns, although Jackson said finding the bug in ice cream is rare.
The outbreak in Blue Bell products is one of the first times it has been seen in ice cream, he said. "Over the years listeria outbreaks have mostly been among soft cheeses, deli meats and other ready-to-eat meats," Jackson said.
Listeria bacteria can live in a food-processing factory for years, sometimes contaminating food products, according to the CDC.
"The question is, why are we seeing this amount of contamination?" Glatter said. "This type of contamination may just lurk in prepared foods," he explained.
Sabra voluntarily recalled its classic hummus after identifying the bacteria in several tubs in Michigan. No illnesses have been reported, state health officials said.
In the Blue Bell matter, the CDC said three people in Texas became ill between 2011 and 2014 after eating the ice cream. Five other illnesses in Kansas from January 2014 to January 2015 were linked to milkshakes made with the company's ice cream.
However, Jackson stressed that, based on CDC data, "there hasn't been an increase in the number of severe [listeria] infections."
The incubation period for listeria is anywhere from three to 70 days, Glatter said, adding symptoms of illness usually develop within two weeks to one month after exposure.
Safe food handling and storage can reduce the likelihood of listeria infection. The CDC says you should:
- Rinse all fresh fruits and vegetables thoroughly
- Scrub firm produce, such as melons and cucumbers, with a produce brush
- Dry produce with a clean cloth or paper towel
- Separate uncooked meats and poultry from vegetables, cooked foods and ready-to-eat foods
- Wash hands, knives, countertops and cutting boards after handling uncooked foods
- Be aware that listeria can grow in foods in the refrigerator. The refrigerator should be 40 degrees Fahrenheit or lower, and the freezer 0 degrees F or lower
- Clean up all spills in the refrigerator, especially juices from hot dog and lunch meat packages, raw meat and raw poultry
- Clean refrigerator walls and shelves
- Cook meat and poultry thoroughly
- Do not drink or cook with unpasteurized milk