Bacillus cereus Outbreak in China Linked to Rice Noodles Prompts Hygiene Concerns

A significant outbreak affecting nearly 200 individuals in China has been attributed to poor hygiene practices at the food producer and inadequate storage conditions at schools, as revealed by a recent study.

Rice noodles behind Bacillus cereus outbreak in China

The outbreak, characterized by acute gastrointestinal illness, unfolded at two middle schools in a rural region of Chongqing in 2021, with the source traced back to Bacillus cereus-contaminated rice noodles.

In May 2021, both schools reported an outbreak, with over 100 students experiencing symptoms such as vomiting and nausea. In response, the Chongqing Center for Disease Control and Prevention and the local CDC initiated an investigation and implemented control measures.

The first school, hosting 55 staff and 536 students, and the second school, with 75 staff and 475 students, are approximately 21 miles apart. The attack rate in the first school significantly surpassed that of the second, with 150 versus 48 cases, and more males than females were affected.

A total of 198 cases were reported, with prevalent symptoms including vomiting, stomach ache, and dizziness. The incubation period ranged from 0.5 to 4.5 hours, with a median incubation period of 2.2 hours, according to the study published in the journal Plos One.

Every morning, all students and staff in both schools consumed breakfast, with rice noodles being a common local food. Notably, all cases had consumed rice noodles from the same food manufacturer.

Issues at the Producer and Schools:

The food producer operated without a valid license for food production, employing three workers, two of whom were responsible for food production but lacked valid health certificates. Poor sanitation conditions were observed at the site, characterized by dust and dirt, with rice stored on the ground and against walls.

Rice noodles produced one morning in May were stored without refrigeration or air conditioning at the manufacturer and distributed to two schools later that day. In the first school, rice noodles were stored at room temperature for 21 hours before cooking, while in the second school, they were kept at room temperature before refrigeration. Local temperatures ranged from 18 to 25 degrees C (64.4 to 77 degrees F).

Bacillus cereus was detected in 20 vomit samples, three anal swabs, and seven rice noodle samples.

Factors Contributing to the Outbreak:

Several factors contributed to the outbreak, according to researchers. The laboratory results indicated that raw rice could have been contaminated with Bacillus cereus. Poor hygiene practices at the food manufacturer facilitated the presence and growth of Bacillus cereus during rice noodle preparation and storage. Inadequate temperature control also played a role in promoting the growth of Bacillus cereus. Moreover, improper storage practices at the schools increased the risk of Bacillus cereus growth.

Preventive Measures and Recommendations:

To prevent future outbreaks, the researchers highlighted the need for the food manufacturer to comply with industrial standards for food production and storage, ensuring that employees involved in food preparation have valid health certificates. Schools were advised to rigorously manage the foods provided to students and staff, encompassing selection, storage, and cooking processes. Additionally, public health efforts should enhance awareness of Bacillus cereus-related food poisoning.