CDC and public health officials in several states investigated multistate outbreaks of Salmonella infections with serotypes of Enteritidis, Hadar, Indiana, Infantis, Mbandaka, and Muenchen.
Epidemiologic and laboratory data showed that contact with backyard poultry made people sick.
Epidemiologic Data
A total of 1,135 people infected with one of the outbreak strains were reported from 48 states, the District of Columbia, and Puerto Rico (see map). The true number of sick people in these outbreaks was likely much higher than the number reported, and these outbreaks may not have been limited to the states with known illnesses. This is because many people recover without medical care and are not tested for Salmonella.
Illnesses started on dates ranging from December 15, 2020, to October 10, 2021 (see timeline). Age information was available for 1,132 people. Their ages ranged from less than 1 to 97 years, with a median age of 37 years. Many were young children: 268 (24%) were under 5 years and 140 (12%) were under 1 year. Of 1,107 people with sex information available, 646 (58%) were female. Of 829 people with information available, 273 (33%) were hospitalized. Two deaths were reported, one from Indiana and one from Virginia.
State and local public health officials interviewed people about the animals they came into contact with the week before they got sick. Of the 677 people interviewed, 449 (66%) reported contact with backyard poultry before getting sick.
Traceback Data
Of 293 people who reported contact with backyard poultry and provided more information, 212 (72%) reported that they bought backyard poultry this year. Purchase locations included feedstores, auctions, and directly from hatcheries. Traceback of these purchases did not identify a single, common source of backyard poultry. A total of 264 separate purchases from more than 150 purchase locations of 70 different companies were reported. At least 17 hatcheries supplied backyard poultry to these purchase locations.
Laboratory Data
Public health investigators used the PulseNet system to identify illnesses that were 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 were closely related genetically. This means that people in these outbreaks likely got sick from the same type of animal.
Public health officials from several states found two of the outbreak strains (Hadar and Enteritidis) from sick people’s backyard poultry and the backyard poultry environment.
- On April 15, public health officials in Ohio found the outbreak strain of Salmonella Hadar from a sick person’s ducklings.
- On May 7, local public health officials in California found the outbreak strain of Salmonella Hadar from a sick person’s duck environment (the ground, duck poop, and duck’s sleeping area).
- On June 1, public health officials in Arizona found the outbreak strain of Salmonella Hadar from a sick person’s chickens and the chicken environment (chickens’ roost and water source).
- On June 15, public health officials in Maryland found the outbreak strain of Salmonella Enteritidis from a sick person’s chickens.
WGS was also used to identify any predicted antibiotic resistance for bacteria from 1,101 sick people’s samples, 4 animal samples, and 7 environmental samples. Of the 1,112 samples, 394 (35%) were predicted to be resistant to one or more of the following antibiotics: amoxicillin-clavulanic acid (0.5%), ampicillin (0.9%), chloramphenicol (0.3%), cefoxitin (0.5%), ceftriaxone (0.5%), ciprofloxacin (0.1%), gentamicin (1.8%), kanamycin (0.4%), streptomycin (33.8%), sulfamethoxazole (2.2%), tetracycline (32.6%), and trimethoprim-sulfamethoxazole (0.2%). Testing of 11 sick people’s samples using standard antibiotic susceptibility testing methods by CDC’s National Antimicrobial Resistance Monitoring System (NARMS) confirmed these results (streptomycin and kanamycin were not tested by this method).
Most people with Salmonella illness recover without antibiotics. However, if antibiotics were needed, some illnesses in these outbreaks may have been difficult to treat with some commonly recommended antibiotics and may have required a different antibiotic choice.
Public Health Action
CDC always advises everyone to take steps to stay healthy around backyard poultry. CDC routinely works with hatcheries and stores that sell poultry to educate new poultry owners and control the spread of Salmonella at hatcheries.
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