A mysterious new outbreak of listeria, which has killed one person, caused pregnancy loss, and hospitalized 13 people in six states, is suspected to be linked to deli meats and cheeses, US health officials said.

The FDA is still investigating the outbreak and has yet to determine its exact source. However, health officials are skeptical of charcuterie and cheese and urge vulnerable groups (pregnant, elderly, children and chronically ill) who are considering eating these foods to be cautious.

(Listeria monocytogenes is a facultative intracellular bacterial pathogen and affects immunocompromised individuals, pregnant women, newborns, and elderly individuals. The main clinical manifestations of Listeria infection are meningitis and meningoencephalitis, bacteremia, and febrile gastroenteritis as a result of central nervous system invasion. Also, the most common infectious agent of rhombencephalitis is L. monocytogenes. In pregnant women, it can cause listerial infection, fetal death, premature birth and infected newborn.)

Listeria spreads easily between the food and the deli environment and can persist for long periods in deli displays and equipment.

Sixteen people fell ill in California, Illinois, Maryland, Massachusetts, New Jersey, and New York. The deceased lived in Maryland.

The outbreak is likely to be much larger, as most people who come into contact with Listeria will not require medical care and will not be tested.