Outbreak, Surveillance, Investigation & Response (OSIR) Journal

The Grammar of Science: “Knots” and “Pieces”

2026-03-21T10:46:28+07:00

An Evaluation of the Village Health Volunteers-based Aedes Larval Indices Surveillance System in Thailand, 2022: A Mixed-methods Study

2026-03-20T07:37:14+07:00

Objectives: To describe the usefulness, processes, and qualitative and quantitative attributes of the Village Health Volunteer-based Larval Indices Surveillance System (VHV-LISS) in Thailand.

Methods: We used a mixed-methods approach to assess three reporting platforms under the VHV-LISS from 1 Jan to 31 Dec 2022. Qualitative analysis encompassed interviews of 57 stakeholders in Chaiyaphum and Mae Hong Son Province, summarized by thematic analysis. Quantitative analysis involved assessing completeness of larval indices data, and comparing the VHV-LISS with another surveillance platform, specifically the “TanRabad” survey.

Results: We found the VHV-LISS to be a long-standing, integrated vector surveillance and control activity conducted by village health volunteers. Although the system is useful for controlling local vectors, community engagement, resource allocation, and stakeholder acceptance varied. Technological constraints, such as volunteer capacity and difficulties in using applications, and inconsistent reporting methods were observed. VHV-LISS platforms provided 85.4% completeness in larval indices data and covered more households than the TanRabad survey. However, the surveillance platform was limited in data accessibility and exchanging mechanisms, and reporting redundancies were evident. Correlation coefficients of larval indices between surveillance platforms ranged from 0.00 to 0.13, which led to low confidence in using the data.

Public Health Recommendations: Standard guidelines and unified larval indices data structures alongside local training and support for village health volunteers are needed to overcome these VHV-LISS limitations.

Descriptive Investigation of a Newly Detected Leprosy Case in Nakhon Si Thammarat, Thailand, 2025

2026-03-20T07:37:06+07:00

Objectives: Newly detected leprosy cases can provide important insights into ongoing transmission and gaps in early diagnosis. In responding to the notification of a 59-year-old Thai female with grade 2 leprosy in Nakhon Si Thammarat Province, Thailand, an investigation was initiated to identify the epidemiological characteristics, assess factors related to the delay in diagnosis and treatment, and determine the source of the disease and whether screening was done among contacts.

Methods: A descriptive investigation was conducted using provincial reports, medical records, patient interviews, and active contact tracing.

Results: The case was diagnosed with multibacillary leprosy with an average bacterial Index of +5.3. Lesions were present on both sides of the body. The duration from onset to diagnosis was 18 years. A factor contributing to the long delay was misdiagnosis by physicians who were not dermatologists and were unaware of leprosy. Screening of 55 close contacts, including 5 household contacts, 47 neighbors, and 3 social contacts, revealed no clinical features consistent with leprosy.

Public health recommendations: All contacts will be followed for 10 years with annual screening. The patient’s medication intake will be monitored and psychological support and social care has been arranged. Thasala hospital should strengthen their early case detection system by looking for cardinal signs of leprosy and by taking a history of risk factors for screening, diagnosis, and treatment.

Role of Nighttime Lights on Cardiovascular Risk in Thailand: A Preliminary Ecological Analysis, 2024

2026-03-20T07:36:59+07:00

Objectives: Nighttime light (NTL) may serve as a proxy for urbanicity and circadian disruption, both of which are relevant to cardiovascular disease (CVD). This study aimed to examine the association between province-level NTL intensity and province-level CVD admission rates.

Methods: We conducted a nationwide ecological study of Thai provinces, linking satellite-derived NTL with 2024 inpatient CVD admissions for adults aged ≥40 years using a nationwide database from the Ministry of Public Health. Admissions for heart failure, acute myocardial infarction (MI), stroke, and atrial fibrillation (AF) were aggregated annually by province. The exposure was the intensity-based location quotient of smoothed nighttime light (LQSNL), using data from the Defense Meteorological Satellite Program—Operational Linescan System for 2010 and, in sensitivity analyses, data from the Suomi National Polar-orbiting Partnership/Visible Infrared Imaging Radiometer Suite for 2023. Associations were assessed with Pearson correlation and linear regression adjusted for the hospital bed capacity.

Results: Provinces with the highest LQSNL quartile had the highest CVD admission rates. LQSNL in 2010 correlated with MI (r 0.31, p<0.001), stroke (r 0.24, p 0.035), and AF (r 0.47, p<0.001) admissions. Using the 2023 LQSNL data yielded similar patterns. In multivariable models, higher LQSNL remained significantly associated with higher admission rates for all CVD outcomes across both exposure years.

Public Health Recommendations: These findings support the use of satellite-derived NTL as a practical proxy for spatial variation in estimating the CVD admission burden, with potential applications in surveillance and resource planning. Given the ecological design and potential for residual confounding, future studies should incorporate individual-level exposure and additional covariates, including demographic, environmental, and health system variables.

Machine Learning Application: Congenital Syphilis Classifier

2026-03-21T10:46:45+07:00

Objectives: Congenital syphilis (CS) is resurging in Thailand, which is challenging the nation's elimination status. Current surveillance relies on manual expert review of paper-based case investigation forms (CIFs), resulting in significant backlogs which hinder timely public health intervention. This study aimed to develop and evaluate an automated system using Large Language Models (LLMs) to digitize and classify CS cases.

Methods: We conducted a retrospective diagnostic study using 143 validated CIFs from Eastern Thailand during October 2024 to October 2025. The system utilized Google Gemini 2.5 Pro and Flash models for optical character recognition (OCR) and a rule-based algorithm for case classification. Cost was estimated by Google Gemini application programming interface (API) pricing. Performance was benchmarked against an expert committee's consensus.

Results: The system efficiently reduced processing time from months to under five minutes at a cost of approximately $0.006 per case. It achieved a data extraction accuracy of 94.2% with a Character Error Rate (CER) of 4.32% for complex handwriting. The overall classification accuracy was 80.0%, with sensitivity 83.3% and specificity of 75.0%. Automated "Red Flags" detection identified inadequate maternal treatment (69.7%) and late antenatal care (32.9%) as primary drivers for confirmed and probable cases.

Public Health Recommendations: The LLM and rule-based classifier offer a scalable "Paper-to-Digital Bridge" for resource-limited settings. While human oversight remains necessary for complex cases, the system functions as an effective high-volume triage tool, transforming retrospective surveillance into real-time actionable intelligence to support the elimination of mother-to-child transmission.

Effectiveness of Pre-exposure Prophylaxis with Tixagevimab–Cilgavimab for COVID-19 Hospitalization among Chronic Kidney Disease Patients in Thailand: A Retrospective Cohort Study, August 2022 to May 2023

2026-03-21T10:46:41+07:00

Objectives: To evaluate the effectiveness of tixagevimab–cilgavimab in preventing COVID-19-related hospitalizations among chronic kidney disease (CKD) patients in Thailand from 1 Aug 2022 to 30 May 2023.

Methods: We conducted a retrospective cohort study using secondary data from Thailand’s national health databases among CKD patients aged ≥12 years under the Universal Coverage Scheme who were followed from 1 Aug 2022 to 30 May 2023. The primary outcome was time until COVID-19 hospitalization, analyzed using Cox regression, and adjusted for age, gender, vaccination status, and comorbidities. Receiving tixagevimab–cilgavimab at a dose of either 300 mg or 600 mg was the main explanatory variable. A stratified analysis was also conducted by history of dialysis.

Results: Among 1,018,175 CKD patients, tixagevimab–cilgavimab recipients had a higher hazard of hospitalization compared to non-recipients (adjusted hazard ratio 1.70; 95% confidence interval (CI) 1.40–2.06). Among dialysis patients, administration of tixagevimab–cilgavimab was associated with a non-significant reduction in the risk of hospitalization (effectiveness 18.15%; 95% CI: -12.82–40.62) while COVID-19 vaccination was strongly protective in both groups, with five doses showing an effectiveness of 79.18% (95% CI 61.28–88.80). Tixagevimab–cilgavimab did not significantly reduce the hazard of hospitalization overall but showed a non-significant trend toward a benefit among dialysis patients.

Public Health Recommendations: Tailored prophylaxis strategies are needed for immunocompromised populations during evolving waves of COVID-19 variants. Further studies should assess effectiveness by variant period and underlying risk profile to better identify subgroups most likely benefit from the interventions.

Dust Alert Device: An Alternative for Real-time PM2.5 Monitoring to Support Disease Surveillance in Thailand with Performance Consistent Relative to Reference Measurements

2026-03-21T10:46:21+07:00

Objectives: To assess the performance of the solar-powered, low-cost Dust Alert Device (DAD) for passive PM_2.5 exposure screening and to evaluate its potential to strengthen air-quality surveillance in Thailand, where the limited spatial coverage of reference monitoring stations limits public health monitoring and risk communication.

Methods: A cross-sectional study was conducted using six DAD units installed between January and December 2024 at the Department of Disease Control and five international checkpoints. Real-time DAD measurements were compared with data from the nearest Air4Thai reference stations. Linear regression analysis was used to examine the relationship between DAD and reference measurements. Mean absolute error (MAE) and mean absolute percentage error (MAPE) were calculated by comparing observed Air4Thai reference with predicted air quality values based on DAD measurements. Sensitivity, and specificity at multiple thresholds (25, 37.5, and 75 µg/m³ for PM_2.5; 45 and 120 µg/m³ for PM₁₀) were also performed.

Results: Hourly PM_2.5 concentrations measured by DAD showed an MAE of 8.6 µg/m³ and an MAPE of 53.6%, and this reduced to 24.2% when PM_2.5 exceeded 37.5 µg/m³ with a sensitivity of 79.6%. The performance of DAD was most consistent with Air4Thai under cool and dry environmental conditions. These findings suggest that DAD is a consistent surveillance-oriented tool that can practically strengthen PM_2.5 monitoring and risk communication.

Public Health Recommendations: Low-cost solar-powered sensors such as DAD can complement national monitoring networks by expanding spatial coverage, particularly in underserved or high-mobility locations such as border checkpoints. Integrating DAD data into routine surveillance and public communication platforms could improve early warning systems, support targeted health advisories, and enhance risk awareness among vulnerable populations. Further calibration methods and environmental adjustment models are recommended to improve accuracy across seasonal and climatic conditions.

Lessons from a Measles Outbreak in a Military School: Rapid Response and Surveillance Gaps in Sattahip District, Chonburi Province, Thailand, 2025

2026-03-21T10:46:25+07:00

Objectives: To confirm a measles outbreak in a military school in Sattahip District, Chonburi Province, Thailand, describe its epidemiologic characteristics, identify associated risk factors, and assess surveillance performance and response timeliness.

Methods: A descriptive and analytical field investigation was conducted among 374 cadets and staff from 30 Jun to 31 Aug 2025. Data were collected through case interviews, environmental assessments, record reviews, and laboratory testing. A retrospective cohort study was performed to identify risk factors. Hospital reporting performance was evaluated, and outbreak response timeliness was assessed using the WHO 7-1-7 detect–notify–respond framework.

Results: Thirty-two measles cases were identified (attack rate 8.6%), all among male cadets. Two waves of transmission occurred, first among second-year cadets and later among first-year cadets. Laboratory testing confirmed measles virus genotype D8 (DSID 9587), genetically related to strains previously detected in the district. Sharing a bathroom with a symptomatic individual (adjusted odds ratio (AOR) 3.12; 95% confidence interval (CI) 1.17–8.33) and close contact with a measles case (AOR 2.31; 95% CI 1.02–5.22) were risk factors, while leaving the school premises was protective (AOR 0.34; 95% CI 0.15–0.74). Outbreak response immunization achieved 100% coverage among cadets and staff and likely interrupted transmission within two incubation periods. Facility-based surveillance evaluation showed low reporting sensitivity (1.04%), indicating underreporting of clinically compatible cases. Although the overall response met the 7-1-7 timeliness targets, delays in symptom reporting and operational constraints were observed.

Public Health Recommendations: Strengthening measles surveillance sensitivity, improving early case reporting, and ensuring rapid outbreak response immunization are essential to prevent transmission in closed institutional settings.

Surveillance Evaluation Matters

2026-03-21T10:46:31+07:00