Foodborne Disease Outbreaks in the United States: A Historical Overview.

Understanding the epidemiology of foodborne disease outbreaks (FBDOs) is important for informing investigation, control, and prevention methods. We examined annual summary FBDO data in the United States from 1938 to 2015, to help understand the epidemiology of outbreaks over time. Due to changes in reporting procedures, before 1998, the mean number of annual outbreaks was 378, and after that, it was 1062. A mean of 42% had a known etiology during 1961-1998; since then the etiology has been identified in approximate to 65%, with a marked increase in the number of norovirus outbreaks. From 1967 to 1997, a mean of 41% of FBDOs occurred in restaurant settings, increasing to 60% in 1998-2015. Concurrently, the proportion of outbreaks occurring at a home decreased from 25% to 8%. The mean size of outbreaks has decreased over time, and the number of multistate outbreaks has increased. Many social, economic, environmental, technological, and regulatory changes have dramatically affected the epidemiology of foodborne disease over time.