Nearly 200 of those sickened are under age 5.
Contact with backyard poultry, such as chicks and ducklings, is the likely source of the disease, which causes diarrhea, fever and stomach cramps, CDC said.
Those sickened reported getting poultry from several sources, including farm stores, websites and hatcheries.
Six of the strains making people sick have been identified in samples from backyard poultry areas at homes in California, Minnesota and Ohio and from retail stores in Michigan and Oregon, CDC said.
The current outbreak is the largest linked to backyard poultry since 2017, when a record 1,120 people were sickened and one died.
To prevent illness, wash your hands thoroughly with soap and water after touching poultry or anything in their environment, CDC advised. If soap and water aren't available, use hand sanitizer.
Never let backyard poultry inside your home. Take care to keep them away from areas where food or drink are prepared, served, or stored, including outdoor patios, the CDC added.
Salmonella infections usually last four to seven days, and most people recover without treatment, the CDC said. If you're concerned about symptoms such as a fever over 102 degrees, blood in your bowel movements or frequent vomiting, see a doctor.