In February and March 2020, four cases of listeriosis were reported by three states, Minnesota (2), Colorado (1), and Texas (1). All four were hospitalized. There were no deaths. The outbreak was assigned CDC identification number 2003MLGX6-1.

The two Minnesota cases reported eating independently at China Buffet in Alexandria, Minnesota on February 15, 2020. Isolates obtained from specimens for the two cases were 0 alleles different by wg MLST and core genome WLST. Both cases ate food from the restaurant's buffet, which included at least 96 different items. Difficulty in procuring a complete list of menu items available on the buffet complicated the investigation.

Food samples were collected from the restaurant for laboratory testing. The decision as to which foods to test was based on foods commonly associated with listeriosis outbreaks. Listeria monocytogenes that was closely related to the clinical isolates was recovered from mung bean sprouts. The restaurant used at least 5 distributors. Mung bean sprouts collected for testing at the restaurant were sourced from Sprouter A. However, sprouts from Sprouter A were received at the restaurant after February 15, the cases' meal date. Cross contamination of another menu item from the sprouts, or contamination of the sprouts from another food item in the restaurant (via employee handling) could not be ruled out. Therefore, the outbreak vehicle of transmission waqs undetermined.