An outbreak of listeria bacteria in deli items across the US has left two dead and at least 13 hospitalised in the past 18 months.

Of 16 reported cases, one person has died in Maryland and a pregnant woman miscarried after catching the illness, according to a US watchdog.

A single food source has not yet been identified, but 11 out of 12 people interviewed reported eating deli-counter meat or cheese prior to becoming ill, the US Centers for Disease Control and Prevention (CDC) reported.

Listeria is a “hardy germ” that can survive and even grow in refrigerators, the CDC said, and spreads easily between counter-top food, hands, deli slicers and surfaces.

In a statement, the watchdog said: “It is difficult for investigators to identify a single food as the source of outbreaks linked to deli meats and cheeses. This is because listeria spreads easily between food and the deli environment and can persist for a long time in deli display cases and on equipment.

“A contaminated food likely introduced the outbreak strain of listeria into delis in multiple states. Investigators are working to identify any specific products or delis that may be contaminated with the outbreak strain.”

The cases, reported between April 17 2021 and September 29 2022, are spread across six states but most were found in New York.

Total numbers are likely to be higher, as some people will have recovered without the need for medical help and not have been tested. More recent cases may also be missing from the numbers as it takes three to four weeks to confirm a case.

Of seven cases in New York state, five bought sliced meat or cheese from US grocery retail chain NetCost Market. However, the international-foods retailer is not believed to be the only source of the bacteria.

“Investigators do not believe that NetCost Market delis are the only source of illnesses… A contaminated food likely introduced the outbreak strain of listeria into delis in multiple states,” the CDC said.

Of the 16 cases for which the CDC has collated data, seven were found in New York state, three in Maryland, two in Massachusetts, two in Illinois, one in California and one in New Jersey.

An estimated 1,600 people get listeriosis each year, and about 260 die, the CDC said.

The news of the outbreak comes after Florida-based seafood supplier Seven Seas International USA yesterday recalled 540 cases of Giant Food private-label smoked salmon after routine testing found potential listeria contamination. No illnesses have been reported, the FDA confirmed.

US producer Old Europe Cheese also recalled several lines of brie and camembert in September and October due to potential listeria contamination.

The bulk brie and camembert cheese were distributed to 80 stores across the US and Mexico, including Albertsons, Whole Foods and Lidl. Six cases have been confirmed in six states, with five hospitalisations.

Last year, Tyson Foods was forced to recall around 8.5 million pounds of frozen cooked chicken products over fears of contamination from the bacteria.

Just Food contacted NetCost Market for comment.