DNA testing links listeria outbreak in NY to Boar's Head deli meat

It was June 17 when epidemiologists at the Centers for Disease Control and Prevention’s headquarters in Atlanta began investigating whether three cases of listeria could be connected.

Was it something those patients ate?

An investigation was underway — developing hypotheses, conducting interviews with the sickened consumers and with deli workers, compiling what had been eaten over prior weeks, analyzing bodily fluids and sequencing DNA.

The culprit, it would turn out: Boar's Head liverwurst.

"So, in the case of this outbreak, we saw, well, geez, everyone in this outbreak seems to be eating these deli meats that were sliced at the delis — so not, like prepackaged — and we were seeing an awful lot of people that were reporting liverwurst, which is a pretty uncommonly consumed deli item nationally," Matthew Wise, chief of the CDC’s outbreak response and prevention branch, told Newsday Tuesday.

On June 26, New York State provided the CDC with DNA sequencing of New Yorkers who had been sickened. On June 27, the CDC connected those cases to the listeria outbreak, according to CDC spokesperson Dave Daigle.

As of this week, the contaminated Boar's Head meat products have left at least three people dead and 43 sickened in 13 states — including three on Long Island and 14 across New York.

The fallout has led to a decline in deli meat sales, grocery stores and local delicatessens have said.

According to the CDC, listeriosis is an infection typically caused by eating food contaminated with the bacterium listeria monocytogenes. About 1,600 people get the infection every year; about 260 die from it. It’s most likely to sicken pregnant women and their newborns, as well as adults 65 or older and those patients who are immunocompromised.

"This is a real bad outbreak," Wise said. "I mean, as you can see, there are a lot of ill people, a lot of severe outcomes."

Nationwide, Wise said, there are about 100 outbreak investigations annually, including salmonella, listeria and E. coli.

For the latest listeria outbreak, CDC investigators have sought help from individual health departments to see where each of the ill patients got the meat, interview deli personnel to learn what companies were involved and compile lot numbers.

The investigation involves not just the CDC but other agencies as well, including the U.S. Department of Agriculture.

The CDC is constantly monitoring DNA fingerprint data being sent in from states to see whether there are multiple people within a short time span sickened from bacteria with the same DNA fingerprinting.

In this outbreak, there was a match.

"In mid-June, CDC flagged that there were several listeriosis illnesses that had that same DNA fingerprint, and then we opened up that multistate investigation," Wise said.

Since late July, Boar’s Head has recalled over 7 million pounds of deli meat after the contamination was traced to its plant in Jarratt, Virginia. They include 71 items produced at the facility between May 10 and Aug. 5 under the Boar’s Head and Old Country brand names, such as liverwurst, ham, bologna, salami, bacon, uncured kielbasa, frankfurters and sausages.

By Matthew Chayes

matthew.chayes@newsday.comchayesmatthew

Matthew Chayes, a Newsday reporter since 2007, covers New York City.