Officials on Friday said that since November at least four people were killed in the United States and 28 people have been sick since a listeria outbreak believed to originate from commercially packaged caramel apples.
Listeria monocytogenes is caused by a bacteria and can cause life-threatening illness. It is particularly dangerous for children, the elderly and pregnant women, in whom it can cause miscarriage.
A total of 83 percent of those interviewed so far (15 of 18 people) said they had recently eaten caramel-coated apples.
The US Centers for Disease Control and Prevention urged consumers in the United States not to eat commercially produced, prepackaged caramel apples until further notice.
"Out of an abundance of caution, CDC recommends that US consumers do not eat any commercially produced, prepackaged caramel apples, including plain caramel apples as well as those containing nuts, sprinkles, chocolate, or other toppings, until more specific guidance can be provided," the CDC said in a statement.
Of the 28 infected, 26 were hospitalized and five people died.
"Listeriosis contributed to at least four of these deaths," said the CDC.
Nine of the cases were pregnancy-related and involved either mothers-to-be or their newborn infants.
Three cases of meningitis, a dangerous complication of listeriosis, otherwise healthy children aged five to 15 were also reported.
The illnesses have spread across 10 states.
Listeria can cause fever, muscle aches, nausea and diarrhea, and symptoms typically begin within a few days to a couple of months after eating a contaminated product.
The bacteria is found in soil, water and animal feces.
Listeria can infect raw vegetables, animal meat, unpasteurized milk and processed foods such as cheese dips and deli meats.