The study did not provide information regarding the source of the contamination.
"These data do not provide information to assess sources of Salmonella or risk factors for invasive disease; demographic characteristics are described as risk indicators. Reported risk factors for infant salmonellosis include exposure to animals, exposure to a household member or attending day care with a child with recent diarrhea, international travel, riding in a shopping cart with raw meat or poultry, and other indoor and outdoor environmental exposures.15,–18 Use of infant formula and lack of breastfeeding are correlated risk markers.15,19,Salmonella has only rarely been identified in commercial formula.20,21 Breastfeeding might be protective because of immunity (eg, maternal antibodies from breastmilk) or to lack of exposure to bottles contaminated by household members."
Pediatrics
https://publications.aap.org/pediatrics/article/doi/10.1542/peds.2021-056140/191251/Epidemiology-of-Salmonellosis-Among-Infants-in-the
ARTICLE| MAY 10 2023
Epidemiology of Salmonellosis Among Infants in the United States: 1968–2015
Julie L. Self, PhD, MPH; Michael C. Judd, MPH; Jennifer Huang, MPH; Patricia I. Fields, PhD; Patricia M. Griffin, MD; Karen K. Wong, MD, MPH
