Investigation Details

Posted November 20, 2023

November 20, 2023

CDC, public health and regulatory officials in several states, and the U.S. Food and Drug Administration (FDA) are collecting different types of data to investigate a multistate outbreak of Listeria monocytogenes infections.

Epidemiologic and laboratory data show that HMC Farms peaches, nectarines, and plums may be contaminated with Listeria and are making people sick.

Epidemiologic Data

As of November 17, 11 people infected with the outbreak strain of Listeria have been reported from seven states (see map). Sick people’s samples were collected from August 22, 2018, to August 16, 2023 (see timeline). Of ten people with information available, all have been hospitalized. One person got sick during their pregnancy and had a preterm labor. One death has been reported from California.

The true number of sick people in this outbreak is likely higher than the number reported, and the outbreak may not be limited to the states with known illnesses. This is because some people recover without medical care and are not tested for Listeria. In addition, recent illnesses may not yet be reported as it usually takes 3 to 4 weeks to determine if a sick person is part of an outbreak.

Public health officials collect many different types of information from sick people or their family, including their age, race, ethnicity, other demographics, and the foods they ate in the month before they got sick. This information provides clues to help investigators identify the source of the outbreak.

The table below has information about sick people in this outbreak (“n” is the number of people with information available for each demographic).

Demographics Information
Table of demographic information (n is the number of people with information available)
Range from 30 to 80 years
Median age of 69
73% are 65 years or older
64% Male
36% Female
80% White
10% Native Hawaiian or other Pacific Islander
10% reported more than one race
89% non-Hispanic
11% Hispanic

State and local public health officials are interviewing people about the foods they ate in the month before they got sick. Of the seven people interviewed, all (100%) reported eating peaches, nectarines, or plums.

CDC conducted a case-case analysis, comparing foods reported by people in this outbreak to foods reported by people who got sick with Listeria but were not part of an outbreak. The analysis showed that people in this outbreak were 18 times more likely to eat peaches, nectarines, or plums (p<0.001) than sick people not in this outbreak. This suggests that peaches, nectarines, and plums are a likely source of this outbreak.

Laboratory Data

Public health investigators are using the PulseNet system to identify illnesses that may be part of this outbreak. CDC PulseNet manages a national database of DNA fingerprints of bacteria that cause foodborne illnesses. DNA fingerprinting is performed on bacteria using a method called whole genome sequencing (WGS).

WGS showed that bacteria from sick people’s samples are closely related genetically. This suggests that people in this outbreak got sick from the same food.

On October 23, FDA collected a sample of HMC Farms peaches for testing and found Listeria in it. On November 6, WGS showed that the Listeria in the peaches are closely related to bacteria from sick people. This means that people likely got sick from eating these peaches.

Public Health Actions

On November 17, HMC Farms recalled whole peaches, plums, and nectarines sold in stores between May 1 and November 15 in 2022 and 2023. CDC is advising people not to eat, sell, or serve recalled fruit.

Previous Updates

Epidemiologic, traceback, and laboratory data show that ice cream made at The Ice Cream House of Brooklyn, NY, has made people sick.

Laboratory and Traceback Data

The New York City Department of Health and Mental Hygiene found the outbreak strain of Listeria in an “Ice Cream House” mini dessert cigar novelty ice cream product and several environmental samples taken from The Ice Cream House. “Ice Cream House” products and “Soft Serve On The Go” ice cream cups are made at the same facility.

Public Health Action

On August 30, 2023, The Ice Cream House recalled all their dairy ice cream and non-dairy frozen dessert products with the “Ice Cream House” logo. Do not eat, sell, or serve recalled products.