Last year’s two Listeria outbreaks are over. And it puts the federal Centers for Disease Control and Prevention (CDC) in an enviable position with no currently active Listeria outbreaks.

Among the foodborne diseases, Listeria is known for its high fatality rate. According to CDC, an estimated 1,600 people get listeriosis each year, mostly from eating food, with death the result for about 260.

When two or more people get the same illness from the same contaminated food or drink, the event is called a foodborne disease outbreak. CDC went most of last year without an active Listeria outbreak to investigated.

Then on Oct. 3, 2018, it learned Johnston County Hams Inc. in Smithfield, NC had recalled ham products for possible contamination with the Listeria bacteria. The outbreak associated with the Johnston County production was declared over on Dec. 18, 2018, but not before one of the four infected people died.

The public also learned of last year’s second Listeria outbreak from a recall. On Nov. 20, 2018, ready-to-eat pork products were recalled for possible Listeria contamination by Long Phung Food Products. Four people in four states were sickened and hospitalized, but all survived. CDC announced that the second outbreak was over on Jan. 29, 2019.

And that left CDC with no active Listeria outbreaks to investigate.

Since both of last year’s Listeria outbreaks involved meat products, the U.S. Department of Agriculture’s Food Safety and Inspection Service (FSIS) assisted CDC in the investigations as did state public health and regulatory officials.

The recalled Long Phung Food Products included all pork patty rolls produced on various dates from May 21, 2018, to Nov. 16, 2018. An undetermined amount of recalled pork patties were shipped to distributors and retailers throughout the nation. In closing out the outbreak, CDC said it is still possible contaminated product could be in home freezers.

CDC told FSIS about a cluster of cluster of listeriosis illnesses that were “closely related” on Oct. 22, 2018. The investigation linked the Listeria monocytogenes illnesses to the ready-to-eat pork products produced by Long Phung Foods.

Four people in four states were infected with the outbreak strain of Listeria monocytogenes. The Listeria specimens from the four infected individuals were collected from July 1, 2017, to Oct. 24, 2018. Both the epidemiologic and laboratory evidence pointed to the Long Phung products as the likely source of the outbreak.

Whole genome sequencing of investigative samples collected from the Long Phung Foods facility on Nov. 19, 2018, were closely related genetically to Listeria monocytogenes from the ill people, FSIS reported.

All four victims were women, ranging in age from 35 to 84. Pregnant women and their newborns, adults over age 65, and people with the weakened immune system are more likely to get listeriosis.

Anyone with a higher risk for Listeria infections should not eat refrigerated pate or meat spreads from a deli or meat counter. Avoid eating hot dogs, lunch meats, cold cuts, other deli meats or sausages unless they are heated to 165 degrees Fahrenheit.

The public health investigation used the PulseNet system to identify illnesses that may have been part of the outbreak. PulseNet is the national subtyping network of public health and food regulatory laboratories coordinated by CDC.

Matching illnesses to the outbreak strain is accomplished with DNA “fingerprinting” of Listeria bacteria using whole genome sequencing (WGS). Illnesses from a common source of infection are closely related genetically.

According to CDC, anyone who thinks they may have stored contaminated pork in a refrigerator or freezer should thoroughly wash and sanitize all drawers and shelves. Listeria bacteria is sometimes very difficult to remove.

Long Phung’s parent company, known as the 165368 C. Corporation, announced this list of recalled products.

CDC used the same tools–DNA fingerprinting, PulseNet, and whole genome sequencing (WGS)–to name Johnston County Hames as the source of Listeria contamination in 2018’s first Listeria outbreak.   That led to the great ham recall of 2018, which was known for removing such name hams from the market as:

• Johnston County Hams, Inc. Country Style Fully Cooked Boneless Deli Ham
• Ole Fashioned Sugar Cured The Old Dominion Brand Hams Premium Fully-Cooked Country Ham with sell-by dates from 4/10/2018 to 9/27/2019
• Padow’s Hams & Deli, Inc. Fully Cooked Country ham Boneless Glazed with Brown Sugar
• Premium Fully-Cooked Country Ham Less Salt Distributed by Valley Country Hams, LLC. with sell-by dates from 4/10/2018 to 9/27/2019
• Goodnight Brothers Country Ham Boneless Fully Cooked

The outbreak led to the recall of hams that were produced between April 3, 2017, through Oct. 2, 2018.

The four people stricken by the first outbreak were from 70 to 81  years of age, half male and half female.   All four required hospitalization and one, a Virginia resident who lived at an assisted living facility, died.

Through routine inspections, deli ham samples were collected from Johnston County Hams in both 2016 and 2018.  The product from both years was found closely related genetically to Listeria strain that caused the outbreak infections.  The results provided more evidence that people infected in the outbreak were contaminated from eating the deli ham.