2019 Outbreak of Listeria Infections Linked to Unknown Source
Final Update
Posted November 7, 2019 at 1:00 PM ET
This outbreak appears to be over. CDC, several states, and federal partners investigated a multistate outbreak of Listeria monocytogenes infections. A single, common source of infections was not identified. Learn more about how you can take steps to prevent Listeria infection.
- Reported Cases: 24
- States: 13
- Hospitalizations: 22
- Deaths: 2
- 24 people infected with the outbreak strain of Listeria monocytogenes were reported from 13 states. No additional ill people were reported after the initial investigation notice on August 23, 2019.
- Of 23 ill people with information available, 22 hospitalizations were reported.
- Two deaths were reported.
- A specific food item, grocery store, food processor, or restaurant chain was not identified as the source of infections in the United States.
- The outbreak appears to be over.
Listeria is most likely to sicken pregnant women and their newborns, adults aged 65 or older, and people with weakened immune systems. People who have underlying medical conditions or take medicines (like steroids or chemotherapy) that lower the body’s ability to fight germs and sickness have weakened immune systems.
Some foods are more likely to contain Listeria. People at higher risk for infection should:
- Heat lunch meats, cold cuts, or other deli meats to an internal temperature of 165°F or until steaming hot just before serving.
- Avoid eating cold smoked fish, unless it is canned or shelf-stable or it is in a cooked dish, such as a casserole. A food is shelf-stable if it can be safely stored at room temperature.
- Choose pasteurized milk and milk products, including soft cheese, ice cream, and yogurt.
- Listeriosis can cause different symptoms, depending on the person and the part of the body affected.
- Pregnant women typically experience only fever and other flu-like symptoms, such as fatigue and muscle aches. However, infections during pregnancy can lead to miscarriage, stillbirth, premature delivery, or life-threatening infection of the newborn.
- People other than pregnant women: Symptoms can include headache, stiff neck, confusion, loss of balance, and convulsions in addition to fever and muscle aches.
- People with invasive listeriosis usually report symptoms starting 1 to 4 weeks after eating food contaminated with Listeria. Some people have reported symptoms starting as late as 70 days after exposure or as early as the same day of exposure.
- Listeriosis is treated with antibiotics.
November 7, 2019
CDC, several states, and federal partners investigated a multistate outbreak of Listeria monocytogenes infections. The outbreak investigation is over and did not identify a specific food item, grocery store, food processor, or restaurant chain as the source of infections.
Public health investigators used the PulseNet system to identify illnesses that may have been part of this outbreak. PulseNet is the national subtyping network of public health and food regulatory agency laboratories coordinated by CDC. DNA fingerprinting is performed on Listeria bacteria isolated from ill people by using a standardized laboratory and data analysis method called whole genome sequencing (WGS). CDC PulseNet manages a national database of these sequences that are used to identify possible outbreaks. WGS gives investigators detailed information about the bacteria causing illness. In this investigation, WGS showed that bacteria isolated from ill people were closely related genetically. This means that people in this outbreak were more likely to share a common source of infection.
As of November 7, 2019, a total of 24 people infected with the outbreak strain of Listeria monocytogeneswere reported from 13 states. A list of the states and the number of cases in each can be found on the Map of Reported Cases page.
Listeria specimens were collected from ill people from July 20, 2017, to August 1, 2019. Ill people ranged in age from 35 to 92 years, with a median age of 72. Sixty-three percent of ill people were female. Of 23 ill people with information available, 22 hospitalizations were reported. Two deaths were reported. No additional ill people were reported after the initial investigation notice on August 23, 2019.
State and local public health officials interviewed ill people to ask about what they ate and other exposures they had before their illness started. CDC analyzed the interview data but did not identify a common food or exposure among ill people.
The Public Health Agency of Canada also investigated an outbreak of Listeria monocytogenes infections in several Canadian provinces linked to cooked diced chicken. Whole genome sequencing showed that the type of Listeria making people sick in Canada was closely related genetically to the Listeria making people sick in the United States, but a source of the infections in the United States was not identified.
