On September 21, 2017, the Central District Health Department received three lab reports and one clinical diagnosis for Salmonella infections of patrons who had all eaten at Chiang Mai House Thai Restaurant, located at 4898 West Emerald Street in Boise, Idaho. In total, six individuals with Salmonella infections were reported to the Central District Health Department and included in the Chiang Mai House Thai Salmonella outbreak (Outbreak ID# 2017-081). Five of the six cases were culture confirmed and were infected with the same strain of Salmonella. All cases ate food prepared at Chiang Mai House Thai on or after September 13. Four out of six of the reported cases consumed contaminated food catered for an office lunch meeting. Reported symptom onset dates ranged from September 16 to September 19.

Environmental Health inspectors conducted an on-site outbreak investigation at the restaurant on September 21. Inspectors observed food preparation and collected environmental swabs and food samples to be tested for Salmonella at the Idaho Bureau of Laboratories. Environmental testing included swabs from the walk-in refrigerator door, meat slicer, cutting boards, and food storage containers. Food samples for testing included prepared egg rolls, curry, and dipping sauces, as well as unprepared cilantro, pork, and eggs. All samples collected tested negative for Salmonella. However, five of the six cases reported eating fresh spring rolls, and the sixth case was not certain what they ate. Therefore, fresh spring rolls are the most likely outbreak vehicle. No employees reported being ill on September 13.

Health Department investigators determined that the Chiang Mai House Thai Restaurant Salmonella outbreak was a point source outbreak that lasted from the evening of September 13 to the morning of September 14. No secondary cases were identified by the health department investigation. The restaurant voluntarily closed on September 22 for 24 hours for deep cleaning and food disposal.