Prepackaged caramel apples blamed for four listeria deaths

An outbreak on prepackaged logged caramel apple has 28 people ill and killed four, the US Centers for Disease Control and Prevention said Friday.

The CDC has issued a warning to the public that all caramel apples already purchased should not be eaten. The agency said it has launched an investigation in collaboration with the Food and Drug Administration in the United States and health authorities of the state.

Listeriosis caused by Listeria monocytogenes, is the most dangerous for people whose immune system is weakened, women who are pregnant and the elderly. Symptoms include stomach pain, fever and muscle pain, and it can also cause encephalitis and bacterial meningitis.

Dr. William Schaffner of Vanderbilt University Medical School, said the incubation period can be up to 70 days. This means that many people have eaten contaminated caramel apples and not yet developed symptoms.

"We can assume that more diseases will come in time," he told ABC News.

The CDC has reported cases of listeriosis have been reported in 10 states across the country. The first was in Minnesota, where four people were sick and died two, all after eating caramel apples.

CDC researchers interviewed 18 people to infection and 15 reported eating caramel apples, the agency said. A fifth died of listeriosis have not been definitively linked to apples.

According to investigators, the apple caramel home, appears to be safe, and the epidemic not seem fresh fruit.

Nine cases of the disease have occurred in pregnant or newborns women. In three cases, children invasive meningitis, a potentially fatal inflammation of the brain or spinal cord developed.