Investigation of a foodborne outbreak at a mass gathering in Petaling District, Selangor, Malaysia.

Objective: On 6 October 2019, Petaling District Health Office received notification of a possible foodborne outbreak involving a mass gathering event. This report presents the processes of diagnosis verification, case identification, determination of associated risk factors and commencement of control measures in managing the outbreak. Methods: Cases were defined as those who attended the mass gathering event on 6 October 2019, consumed the pre-packaged food and subsequently developed vomiting, abdominal pain, diarrhoea or other symptoms (e.g. fever, nausea and dizziness). Epidemiological, environmental and laboratory investigations were performed. Data were analysed using SPSS software (version 24.0). Results: A total of 169 cases were identified. The attack rate was 7.2%, and cases ranged in age from 7 to 50 years, with a median of 20 years. A total of 156 (92.3%) cases had vomiting, 137 (81.1%) had abdominal pain and 83 (49.1%) had diarrhoea. Consuming nasi lemak at the mass gathering was found to be significantly associated with developing illness (odds ratio: 9.90, 95% confidence interval: 6.46-15.16). The samples from suspected food, food handlers and the environment were positive for Bacillus cereus, Staphylococcus aureus or coliforms. Discussion: The outbreak at this mass gathering was probably caused by food contaminated with B. cereus and S. aureus. To prevent future outbreaks, we recommend mass gathering events use certified catering services that have adequate food safety training.

Descriptive epidemiology of the first wave of COVID-19 in Petaling District, Malaysia: Focus on asymptomatic transmission.

BACKGROUND: COVID-19 was first detected in Malaysia on 25 January 2020. Multiple clusters were detected in Petaling District, with the first locally transmitted case reported on 8 February. Descriptive analyses of the epidemiology of the COVID-19 outbreak in Petaling are presented, from the first case to the end of the first wave. METHODS: All laboratory-confirmed COVID-19 cases reported to the Petaling District Health Office between 1 February and 26 June 2020 were analysed. Socio-demographic characteristics, symptoms, date of onset, date of exposure, travel history and history of comorbidities were obtained by phone interviews using one of two investigation forms. The descriptive analysis was conducted according to time, place and person. RESULTS: There were 437 COVID-19 cases, for an incidence rate of 24/100 000 population. Ten (2.3%) deaths and 427 recovered cases were recorded. Of the 437 cases, 35.5% remained asymptomatic and 64.5% were symptomatic. Common symptoms included fever (43.8%), cough (31.6%) and sore throat (16.2%); 67.3% had no comorbidities, 62.5% reported close contact with a confirmed case, and 76.7% were local infections. Transmission occurred in four main groups: religious gatherings (20.4%), corporations (15.1%), health facilities (10.3%) and a wholesale wet market (6.4%). In 31.9% of confirmed cases, an epidemiological link to an asymptomatic case was found. CONCLUSION: Transmission of the disease by asymptomatic cases should be emphasized to ensure continuous wearing of face masks, hand hygiene and social distancing. Further research should be conducted to better understand the transmission of SARS-CoV-2 from asymptomatic cases.