December 17, 2020

In 2020, CDC and public health officials in all 50 states investigated 17 multistate outbreaks of Salmonella infections linked to backyard poultry.

Public health investigators used the PulseNet system to identify illnesses that were 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 Salmonella 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 December 17, 2020, a total of 1,722 people infected with one of the outbreak strains of Salmonella were reported from all 50 states. A list of the states and the number of cases in each is on the Map of Reported Cases page.

Illnesses started on dates from January 14, 2020, to November 27, 2020. Ill people ranged in age from less than 1 year to 95 years, with a median age of 35. Children younger than 5 accounted for 24% of ill people. Of ill people, 59% were female. Of 1,004 people with information available, 333 (33%) were hospitalized. One death in Oklahoma was reported.

If antibiotics were needed, some infections related to these outbreaks may have been difficult to treat with some commonly recommended antibiotics and may have required a different antibiotic choice. Whole genome sequencing performed on Salmonella bacteria isolated from 1,641 ill people and two environmental samples showed predicted antibiotic resistance to one or more of the following antibiotics for 848 isolates:

• amoxicillin-clavulanic acid (1.5%)
• ampicillin (3.2%)
• cefoxitin (1.5%)
• ceftriaxone (1.5%)
• chloramphenicol (0.7%)
• ciprofloxacin (0.1%)
• fosfomycin (2.1%)
• gentamicin (1.2%)
• kanamycin (0.5%)
• streptomycin (45.6%)
• sulfisoxazole (3.7%)
• tetracycline (46.0%)
• trimethoprim-sulfamethoxazole (1.7%)

There was no antibiotic resistance predicted for 795 (48.4%) isolates. Testing of 13 outbreak isolates using standard antibiotic susceptibility testing by CDC’s National Antimicrobial Resistance Monitoring System (NARMS) laboratory showed resistance to streptomycin and tetracycline in 3 isolates and no resistance in 10 isolates (fosfomycin and kanamycin were not tested by this method).

Investigation of the Outbreaks

Epidemiologic and laboratory evidence showed that contact with backyard poultry (such as chicks and ducklings) was the likely source of these outbreaks.

In interviews, ill people answered questions about animal contact and other exposures in the week before they became ill. Of 876 people interviewed, 576 (66%) reported contact with chicks and ducklings before becoming ill.

Testing of backyard poultry and their environments (such as backyard coops) in Kentucky and Oregon found three of the outbreak strains.

Ill people reported buying poultry from many sources, including agricultural stores, websites, and hatcheries. No single store chain or hatchery could account for all of the illnesses.

Regardless of where backyard poultry are purchased, they can carry Salmonella germs that can make people sick. Backyard poultry owners should always follow steps to stay healthy around their flocks.

As of December 17, 2020, this outbreak investigation is over. CDC will continue to work with partners to prevent Salmonella infections linked to contact with backyard poultry.