Outbreak Summary

CDC, public health and regulatory officials in several states, and the U.S. Food and Drug AdministrationExternal (FDA) investigated this multistate outbreak of Salmonella infections.

Public health investigators used the PulseNet system to identify illnesses that were part of this outbreak. PulseNet is the national subtyping network of public health and food regulatory agency laboratories coordinated by CDC. DNA fingerprinting was performed on Salmonella bacteria isolated from ill people by using techniques called pulsed-field gel electrophoresis (PFGE) and whole genome sequencing (WGS). CDC PulseNet manages a national database of these DNA fingerprints to identify possible outbreaks. WGS gives a more detailed DNA fingerprint than PFGE.

As of May 24, 2018, 199 people infected with the outbreak strains of Salmonella were reported from 41 states. A list of the states and the number of cases in each can be found on the Case Count Map page.

Illnesses started on dates ranging from January 11, 2017 to May 8, 2018. Ill people ranged in age from less than 1 to 75 years, with a median age of 38. Among ill people, 52% were male. Of 132 people with available information, 50 (38%) were hospitalized. No deaths were reported.

Whole genome sequencing analysis did not identify any predicted antibiotic resistance in isolates from 111 ill people and 61 kratom samples. Testing of 17 clinical isolates using standard antibiotic susceptibility testing methods by CDC’s National Antimicrobial Resistance Monitoring System (NARMS) laboratory also did not show any antibiotic resistance.

Investigation of the Outbreak

Epidemiologic and laboratory evidence indicated that kratom was the likely source of this multistate outbreak. Kratom is a plant consumed for its stimulant effects and as an opioid substitute.

State and local health officials interviewed ill people to ask about the foods they ate and other exposures before they became ill. Seventy-six (74%) of 103 people interviewed reported consuming kratom in pills, powder, or tea. Most people reported consuming the powder form of kratom. People who reported consuming kratom purchased it from retail locations in several states and from various online retailers.

This outbreak was detected when a cluster of people infected with Salmonella I 4,[5],12:b:- was identified by CDC PulseNet. During the investigation, health and regulatory officials in several states and the FDA collected various leftover and unopened kratom products to test for Salmonella contamination. As additional strains of Salmonella were identified in kratom products, a search of the CDC PulseNet database identified ill people infected with some of these strains, including Salmonella Heidelberg, Salmonella Javiana, Salmonella Okatie, Salmonella Weltevreden, and Salmonella Thompson. These ill people were added to the outbreak investigation. Eighty-five different DNA fingerprints of Salmonella bacteria were identified in samples of kratom products. The FDA website has a list of contaminated kratom productsExternal , which were from several retail locations and online retailers. Several companies issued recalls of kratom products. A list of the recalled kratom productsExternal is also available on the FDA website.

This outbreak investigation is over. However, some kratom products that were contaminated with Salmonella have not yet been recalled and may still be available for purchase or in people’s homes. People who are at risk of severe Salmonella infection should avoid consuming kratom to prevent infection.