A Multiple-Serotype Outbreak of <i>Salmonella</i> Infections Linked to Kratom, United States, 2017–2018

Abstract

In early 2018, we investigated a large national multiple-serotype <i>Salmonella</i> outbreak linked to contaminated kratom, a raw minimally processed botanical substance. Kratom is a plant consumed for its stimulant effects and as an opioid substitute. A case was defined as a laboratory-confirmed <i>Salmonella</i> infection with one of the outbreak strains (serotypes I 4,[5],12:b:-, Heidelberg, Javiana, Okatie, Weltevreden, or Thompson) with illnesses onset during January 11, 2017-May 8, 2018. State and local officials collected detailed information on product consumption and sources. Suspected products were tested for <i>Salmonella</i> and traceback was conducted to determine product distribution chains and suppliers. We identified 199 cases from 41 states; 54 patients were hospitalized. Early interviews indicated kratom was an exposure of interest. Seventy-six (74%) of 103 people interviewed reported consuming kratom in pills, powders, or teas. Multiple serotypes of <i>Salmonella</i> were detected in samples of kratom collected from the homes of the patients and from retail locations. Several companies issued recalls of kratom products due to <i>Salmonella</i> contamination. To the authors' knowledge, this investigation is the first to establish kratom as a vehicle for <i>Salmonella</i> infection. Our findings underscore the serious safety concerns regarding minimally processed botanical substances intended for oral consumption and the challenges in investigating outbreaks linked to novel outbreak vehicles.