Investigation of a Methemoglobinemia Outbreak Caused by Eating Sausages with High Concentrations of Nitrates and Nitrites in Trang Province, Thailand, January 2022

In late January 2022, a cluster of methemoglobinemia cases across five provinces of Thailand was notified to the regional public health authorities. A joint investigation was conducted aiming to describe characteristics of the outbreak in one of the provinces, traceback the suspected food, and recommend prevention and control measures. We conducted a cross-sectional descriptive study, interviewing the cases, reviewing their medical records, and interviewing their parents and treating physicians. An active case finding was conducted. A probable case was defined as a person who presented with acute central cyanosis with oxygen saturation less than 92% by pulse oximetry. Suspected food samples were collected for nitrates and nitrites testing. Three cases (2 males, 1 female) were identified and there was no death. Their ages ranged from 8–12 years. The sausages came from the same source and were found to have high concentrations of nitrates (1,270.8–1,690.0 mg/kg) and nitrites (3,554.5–3,776.2 mg/kg). The sausages were identified as a likely cause of the outbreak. Government regulation, product liability laws, and food safety concerns among food retailers and customers are important to reduce the impact of consuming unsafe foods.