Outbreak, Surveillance, Investigation & Response (OSIR) Journal

Epidemiological Fallacy: a Common Mistake Among Epidemiologists

2026-09-08T13:53:08+07:00

A Clostridium perfringens Food Poisoning Outbreak in a School Caused by Precooked Pork Skin, Thailand, 2024

2026-09-23T09:05:06+07:00

Objectives: In September 2024, a food poisoning outbreak occurred at a school in Buriram, a northeastern province of Thailand. We investigated to confirm the outbreak and diagnosis, describe its epidemiological characteristics, identify the source, and provide recommendations.

Methods: We reviewed food poisoning situations and conducted an active case finding in the school. A suspected case was anyone at the school between 17–21 Sep 2024 with diarrhea or vomiting; confirmed cases had gastrointestinal pathogens detected in stool specimens or rectal swabs. We conducted interviews on food preparation and a matched case-control study using conditional logistic regression model to identify the contaminated food. Samples of food, water, and utensils were also tested for bacterial and viral contamination.

Results: A total of 658 cases were reported (attack rate of 40.0%), 97.1% presenting with watery diarrhea. The outbreak began on 17 September in the afternoon, peaked that night, and ended on 21 September. Analytical study implicated spicy pork salad from 17 September lunch as the source (adjusted odds ratio 18.99, 95% confidence interval 1.86–193.70). Investigation revealed that its ingredient, precooked pork skin, was improperly stored and the cooked lunch was not reheated before serving. Testing confirmed Clostridium perfringens in 17 cases, as well as in leftover spicy pork salad and pork skin samples.

Public Health Recommendations: This incident highlights the risks of improper food handling. We recommend avoiding keeping food ingredients at room temperature, thorough reheating precooked ingredients, and adherence to food safety standards for the school canteen.

Knowledge Assessment of Dog Bite and Rabies Management among Health Workers in the Border Region of Timor-Leste

2026-09-24T19:11:57+07:00

Objectives: Rabies emerged as a significant public health threat in Timor-Leste following the first laboratory-confirmed outbreaks in 2024. The Região Administrativa Especial de Oé-Cusse Ambeno (RAEOA) border region has been disproportionately affected, recording over 800 dog bite cases and five human deaths between 2023 and 2024. This study assessed healthcare workers’ (HCWs) knowledge of rabies transmission, prevention, and dog bite management to identify gaps and strengthen the local health response.

Methods: A quantitative knowledge survey was conducted from 14 to 22 April 2024. Using convenience sampling, data was collected from 164 HCWs across seven health facilities in the RAEOA region. Descriptive statistics were presented, while inferential analysis using Analysis of Variance was performed to examine differences in knowledge scores across professional cadres and health facilities.

Results: The mean age of the 164 participants was 34 years (SD 8.84). Nurses (25.6%) and allied technicians (20.1%) comprised the largest professional groups. Overall knowledge was high, with a mean score of 80%; 37.2% achieved a perfect score of 17/17. Significant differences in knowledge scores were observed by profession (p-value 0.018) and workplace (p-value 0.006), with doctors and midwives achieving the highest mean scores. However, only 40.8% of respondents correctly identified rabies’ near-100% fatality rate, and only 71.9% knew Category III wounds should not be sutured.

Public Health Recommendations: HCWs in the RAEOA region demonstrated strong knowledge of rabies transmission, prevention, and management. However, disparities across professional cadres and health facilities underscore the need for targeted, continuous training, equitable resource distribution, and strengthened surveillance systems. Rabies control efforts should adopt a One Health approach integrating human health surveillance, dog vaccination, and cross-border coordination.

Situation Analysis of Rabies Surveillance and Dog Bite Management in Manufahi Municipality of Timor-Leste, 2025: A Mixed-Methods Quality Data Audit

2026-09-30T08:54:09+07:00

Objectives: Rabies has emerged as a significant public health threat in Timor-Leste, with 24 recorded human deaths since the disease first appeared in early 2024. While initially concentrated in border areas, the virus has spread to multiple municipalities, including Manufahi Municipality. This study presents a situational analysis of dog bite management concerning rabies risk, the timeliness of surveillance reports, and operational factors in Manufahi Municipality during 2025.

Methods: A mixed-methods quality data audit was employed across four community health centers. Data collection encompassed direct observations of clinical areas, semi-structured interviews with 17 essential health personnel, and a methodical review and cross-verification of outpatient and laboratory register books.

Results: The surveillance system achieved 100% timeliness in weekly reporting. In 2025, Manufahi Municipality recorded 295 dog bite cases, corresponding to an incidence of 4.63 per 1,000 population. Two patients (0.7%) died with clinical signs consistent with rabies. Children aged 5 to 14 years had the highest burden, accounting for 52.9% of cases. While vaccines arrived in June 2025, first-dose anti-rabies vaccine (ARV) coverage reached 84.4% overall (249/295) and 87.7% among eligible category II and III exposures (249/284). However, multi-dose adherence dropped to 28.9% (2 doses; 82/284) and 7.0% (3 doses; 20/284). Rabies immune globulin (RIG) coverage was 13.7% (31/226) among high-risk category III cases.

Public Health Recommendations: Improving rabies control requires standardizing reporting formats and prioritizing the digitalization of surveillance systems. Adopting a "One Health" approach and enhancing community-level vaccine accessibility are vital for sustainable disease elimination.

Rapid-onset Gastrointestinal Illness Following a Funeral Ceremony in Northern Thailand: A Staphylococcal Food Poisoning Outbreak Investigation, June 2025

2026-10-01T05:52:26+07:00

Objectives: On 15 Jun 2025, a cluster of acute gastrointestinal illness cases was reported among attendees of a funeral ceremony in Phayao Province, Thailand. We conducted an investigation to identify the etiology and describe the epidemiological characteristics of the outbreak, determine associated risk factors, and recommend prevention and control measures.

Methods: A suspected case was defined as any person who attended the funeral or consumed food served at the event and developed at least one gastrointestinal symptom during 15–17 Jun 2025. An active case finding together with interviews, medical record reviews, environmental assessments and laboratory testing of clinical, food handler, and food specimens were conducted. A retrospective cohort study was conducted. Multivariable logistic regression was used to estimate adjusted odds ratios (AORs) with 95% confidence intervals (CIs).

Results: Among 311 participants, 188 cases were identified (60.5%). Common symptoms were nausea (89.9%), vomiting (83.5%), abdominal pain (71.3%), and diarrhea (53.2%). The shortest incubation period was one hour, and the median was four hours (interquartile range 3–5 hours). All cases reported consumption of red pork with rice, with no illness among unexposed participants. In multivariable analysis, rice (AOR 21.34; 95% CI 3.19–142.75) and boiled eggs (AOR 3.10; 95% CI 1.08–8.92) were associated with illness. Methicillin-susceptible Staphylococcus aureus was isolated from vomitus, food samples, and a food handler’s hand swab. Environmental assessment identified prolonged storage of food at room temperature, inadequate hand hygiene practices, reuse of ice, and low residual free chlorine levels.

Public Health Recommendations: Findings supported staphylococcal food poisoning associated with contaminated food. Proper hand hygiene, prevention of cross-contamination, safe food storage, temperature control, strengthened food safety training, and improved catering supervision are recommended.

Estimating the Public Health Impact of MERS-CoV Vaccination in Thailand: A Simulation-Based Approach

2026-10-01T05:52:21+07:00

Objectives: Middle East Respiratory Syndrome coronavirus (MERS-CoV) remains a public health concern for Thailand, because of the risk of importation from Thai pilgrims attending the Hajj. With MERS-CoV vaccines under development, evidence on their potential impact is needed for vaccination planning. This study aimed to estimate the potential public health impact of MERS-CoV vaccination among Thai pilgrims attending the Hajj under different vaccine effectiveness (VE) and transmission scenarios.

Methods: A compartmental model simulated MERS-CoV transmission among Thai and non-Thai pilgrims attending the Hajj over 30 days. Vaccination was applied only to Thai pilgrims before travel. VE scenarios of 30%, 50%, 70%, and 90% were compared with no vaccination across basic reproduction number (R₀) values of 1, 2, 4, 6, and 8. Outcomes included infection burden and transmission dynamics, severe cases, deaths, and timing of case occurrence.

Results: Increasing VE reduced the projected number of infections, severe cases, and deaths across all transmission scenarios. Without vaccination, cumulative infections among Thai pilgrims increased from 0.35 cases at R₀=1 to 60.69 cases at R₀=8. At R₀=8, cumulative incident cases over the 30-day simulation period decreased from 60.69 without vaccination to 6.05 with 90% VE. During the 30-day simulation, the maximum observed daily incidence decreased from 10.15 to 1.01 cases, and the maximum observed prevalence decreased from 33.65 to 3.36 cases. Cumulative severe cases decreased from 15.43 to 1.54 and deaths from 5.66 to 0.57. Vaccination also delayed prevalent cases reaching ≥1 case—the threshold for prompt notification—from day 10 to day 23.

Public Health Recommendations: Under lower-transmission conditions, routine vaccination of all Thai pilgrims may not be necessary. However, if MERS-CoV transmission or outbreak activity increases in Saudi Arabia, targeted vaccination should be considered if a safe and effective vaccine becomes available. Further studies should evaluate cost-effectiveness and the combined effects of vaccination and non-pharmaceutical interventions.

Cost-effectiveness of Expanding Syphilis Screening and Diagnosis under Thailand’s Universal Coverage Scheme

2026-10-01T05:52:24+07:00

Objectives: The existing syphilis screening approach is insufficient in lowering the overall incidence of syphilis within the population. The current approach falls short of the World Health Organization 2030 elimination benchmarks (congenital syphilis <50 per 100,000 live births and a 90% reduction in incidence). This study aims to evaluate the cost-effectiveness of expanding syphilis screening and diagnosis in Thailand and its budget implications.

Methods: Decision tree models were developed to estimate the number of syphilis cases detected and determine associated healthcare costs. The analysis adopted the payer perspective (National Health Security Office), with the current Universal Coverage Scheme (UCS) targeted-screening practice as the base scenario. Inputs were drawn from national surveillance, program service data, published test-performance studies, and standard cost references. The evaluation compared Thailand’s current UCS screening package with an enhanced strategy that encompasses a broader population and incorporates rapid diagnostic tests in addition to the current laboratory-based treponemal serological assessments. The primary outcomes included the number of syphilis cases detected and the incremental cost-effectiveness ratio, defined as the additional cost per case detected. A five-year budget impact analysis from the 2022 base year was also conducted.

Results: Expanding screening to all Thais with high-risk behaviors increased the total costs but improved the unit-cost efficiency and was more cost-effective than targeting specific groups. The cost per case detected was lowest for expanding to all high-risk Thais (19,870 Thai baht (THB); US$567), compared to current practice (22,064 THB; US$629) and prisoners-and-youth (20,549 THB; US$586). Overall, annual budget expenditure is projected to increase from 149 million THB (US$4.25 million) to 169 million THB (US$4.82 million).

Public Health Recommendations: Extending screening to all high-risk Thais is more beneficial and cost-effective than restricting it to specific subgroups. We recommend integrating this strategy into existing routine disease-screening programs, such as HIV testing, to address HIV and syphilis together.

The Grammar of Science: Lost in Statistics? A Practical Roadmap for Biomedical and Health Research

2026-09-08T14:05:18+07:00