Relapse of infant botulism. We report on 3 infants who had relapse of infant botulism after apparent resolution of clinical symptoms. This group represented 5% of the infants with confirmed infant botulism who were treated at our institution since 1976. The exact cause for these relapses was unclear, but three potential mechanisms are examined. There were no historical, clinical, or electrophysiological predictors of relapse. Although at the time of writing recovery from relapse appeared complete, close follow-up of patients recovering from a bout of infant botulism is necessary. 