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Investigation Details
Posted May 23, 2024
CDC and public health officials in several states are collecting different types of data to investigate multistate outbreaks of Salmonella Altona, Indiana, Infantis, Mbandaka, and Typhimurium infections.
Epidemiologic, laboratory, and traceback data show that contact with backyard poultry is making people sick.
Epidemiologic Data
As of May 16, 2024, 109 people infected with one of the outbreak strains of Salmonella have been reported from 29 states (see map). Illnesses started on dates ranging from February 28, 2024, to April 30, 2024 (see timeline). Of 82 people with information available, 33 (40%) have been hospitalized. No deaths have been reported.
The true number of sick people in an outbreak is likely much higher than the number reported, and the outbreak may not be limited to the states with known illnesses. This is because many people recover without medical care and are not tested for Salmonella. 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, including their age, race, ethnicity, other demographics, and the animals they came into contact with, in the week 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 |
|---|---|
| Age (n=109) |
Range from <1 to 93 years Median age of 10 43% under 5 years |
| Sex (n=107) |
55% female 45% male |
| Race* (n=74) |
89% White 4% African American/Black 1% Native American or Alaska Native 1% Asian 1% Native Hawaiian or other Pacific Islander 3% reported more than one race |
| Ethnicity (n=74) |
80% non-Hispanic 20% Hispanic |
* Percentages do not total 100 due to rounding.
State and local public health officials are interviewing people about the animals they came into contact with in the week before they got sick. Of the 70 people interviewed, 51 (73%) reported contact with backyard poultry.
Traceback Data
Of 27 people with information available, 18 (67%) reported purchasing or obtaining poultry before their illness started. People reported purchasing poultry from multiple retail stores and directly from a hatchery. Multiple hatcheries supplied birds to the retail stores. A common poultry supplier has not been identified across all outbreaks.
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 gastrointestinal 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 means that people in this outbreak likely got sick from the same type of animal.
Investigators in Ohio and Utah collected samples from inside the boxes used to ship poultry from hatcheries to retail stores, including the box liner and bedding. WGS showed that the Salmonella Altona and Salmonella Mbandaka found in these samples are the same strain as the ones found in sick people.
WGS analysis of bacteria from 101 people’s samples and four environmental samples had no predicted resistance; seven people’s samples predicted resistance to one or more of the following antibiotics: amoxicillin-clavulanic acid, ampicillin, cefoxitin, ceftiofur, ceftriaxone, chloramphenicol, ciprofloxacin, gentamicin, kanamycin, streptomycin, sulfisoxazole, and tetracycline. More information is available at the National Antimicrobial Resistance Monitoring System (NARMS) site. Most people with Salmonella illness recover without antibiotics. However, if antibiotics are needed, some illnesses in this outbreak may be difficult to treat with some commonly recommended antibiotics and may require a different antibiotic choice.
Public Health Actions
CDC advises everyone to take steps to stay healthy around backyard poultry. CDC and state partners are working with hatcheries and stores that sell poultry to educate new poultry owners and control the spread of Salmonella.
CDC and public health officials in several states are collecting different types of data to investigate multistate outbreaks of Salmonella infections with serotypes Braenderup, Enteritidis, Indiana, Infantis, Mbandaka, and Typhimurium.
Epidemiologic data show that contact with backyard poultry is making people sick.
Epidemiologic Data
Since the last update on June 15, 280 more illnesses have been reported. As of July 12, a total of 690 people infected with one of the outbreak strains have been reported from 47 states and Puerto Rico (see map). Illnesses started on dates ranging from January 1, 2023, to June 30, 2023 (see timeline). Of 459 people with information available, 141 (31%) have been hospitalized. No deaths have been reported.
The true number of sick people in an outbreak is likely much higher than the number reported, and the outbreak may not be limited to the states with known illnesses. This is because many people recover without medical care and are not tested for Salmonella. 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, including their age, race, ethnicity, other demographics, and the animals they came into contact with during the week 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 |
|---|---|
| Age (n=672) |
Range from 1 month to 92 years Median age of 31 23% under 5 years |
| Sex (n=674) |
57% female 43% male |
| Race (n=455) |
92% White 2% African American/Black 2% Native American or Alaska Native 1% Asian 1% Native Hawaiian or other Pacific Islander 3% reported more than one race |
| Ethnicity (n=438) |
93% non-Hispanic 7% Hispanic |
State and local public health officials are interviewing people about the animals they came into contact with in the week before they got sick. Of the 390 people with information about animal contact, 314 (81%) reported contact with backyard poultry before getting sick. Of 296 people who were asked about eggs from their backyard poultry, 78 (26%) reported eating eggs from their flock.
Laboratory and Traceback Data
Investigators in Michigan, Minnesota, Nevada, Utah, and Wisconsin collected samples from the areas where chicks are housed in stores or at sick people’s homes. Whole genome sequencing (WGS) showed that Salmonella Braenderup, Enteritidis, Mbandaka, and Infantis found in the poultry’s environments are closely related to bacteria from sick people. Poultry that lived in these environments were supplied to stores or poultry owners by at least four different poultry hatcheries.
Of 242 people with information on poultry purchases, 187 (77%) reported purchasing or obtaining poultry after January 1, 2023. Forty-four people reported purchasing poultry from multiple locations. People reported purchasing or obtaining poultry from at least 178 different locations, and 10 people reported purchasing poultry directly from hatcheries online. Investigators are continuing to work with stores and hatcheries that are identified during the investigation to find ways to reduce Salmonella in poultry.
WGS analysis was used to predict resistance to antibiotics for bacteria from 688 people’s samples. Of these, 64 (9%) were predicted to be resistant to one or more of the following antibiotics: amoxicillin-clavulanic acid, ampicillin, cefoxitin, ceftiofur, ceftriaxone, ciprofloxacin, gentamicin, streptomycin, sulfamethoxazole, and tetracycline. Bacteria from the remaining 624 samples had no predicted resistance. Testing of bacteria from 8 sick people’s samples using standard antibiotic susceptibility testing methods by CDC’s National Antimicrobial Resistance Monitoring System (NARMS) largely confirmed these results. Streptomycin and ceftiofur were not tested by this method, and one person’s sample showed resistance to colistin. (NARMS added colistin to the list of drugs tested for Salmonella in 2020; resistance is defined as a minimum inhibitory concentration [MIC] of ≥4 µg/mL. Some Salmonella serotypes may have higher MICs naturally, even without acquired resistance identified.) Most people with Salmonella illness recover without antibiotics. However, if antibiotics are needed, this resistance is unlikely to affect the choice of antibiotic used to treat most people.
Public Health Actions
CDC advises everyone to take steps to stay healthy around backyard poultry. CDC and state partners are working with hatcheries and stores that sell poultry to educate new poultry owners and control the spread of Salmonella at hatcheries.
