Descriptive epidemiology of infant botulism in the United States, 1976-2006

Background: Infant (intestinal toxemia) botulism (IB) was first recognized as a novel infectious disease in 1976 in California that manifest clinically as an acute flaccid paralysis. Coincident with the recognition of IB, CDPH began surveillance and research activities to identify risk factors and modes of transmission that were subsequently continued jointly by CDPH and CDC.

Methods: Complete case ascertainment in California has been accomplished through statewide diagnostic testing provided by the CDPH infant botulism laboratory. CDC identified cases in non-California states through a passive reporting system combined with providing diagnostic laboratory testing to approximately 30 states.

Results: In the 30 years 1976 – 2006 a total of 2417 laboratory-confirmed cases of IB were hospitalized in the US; 9 outpatient cases were also recognized. Approximately 50% of hospitalized cases required intubation and mechanical ventilation. More than 91% of cases occurred between one week and six months of age in a unique age distribution. Formula-fed infants were significantly younger at onset of illness (8.1 wks, mean) than were breast-fed infants (15.6 wks, mean). Cases occurred in all major racial and ethnic groups. Incidence was higher in the western US, Alaska, Hawaii and five contiguous Mid-Atlantic states. Feeding honey to infants was the only identified avoidable risk factor for contracting IB.

Conclusions: Infant botulism occurs nationwide. Most cases were identified because their acute paralysis necessitated hospitalization. The full clinical spectrum of illness remains unascertained. The role of dietary influences, especially breast and formula feeding, awaits clarification through a California case-control study now undergoing analysis.