Outbreak, Surveillance, Investigation & Response (OSIR) Journal

A Typhus and Typhoid Fever Outbreak: A Diagnostic Dilemma in Joypurhat District, North-western Bangladesh, 2021

Wed, 31 Dec 2025 00:00:00 +0700

Typhoid (enteric) and typhus (Rickettsia) fevers are endemic in Bangladesh. This study describes an outbreak initially thought to be typhoid fever, but upon several patients’ non-response to treatment, further evaluation discovered that these patients had typhus. One typhoid case did not respond to ceftriaxone (although sensitive in blood culture) and, due to empirical knowledge of the physician, was diagnosed as typhus by a significant Weil–Felix test and responded to doxycycline. A total of 241 cases were identified: 158 (65.6%) cases of typhoid fever, 44 (18.2%) with typhus, and 39 (16.2%) with typhoid and typhus co-infections. In this outbreak, cases in the spotted fever group rickettsia (SFGR) constituted the largest proportion, followed by the typhus group (TG), while the scrub typhus group (STG) had the smallest proportion. This finding was different from the typical subgroup pattern seen in Bangladesh of TG>STG>SFGR. Typhus may be misdiagnosed as typhoid fever due to similar clinical presentation, so it is essential for physicians to distinguish between the diseases because of different treatment and intervention modalities. Epidemiologists should be aware that both diseases can occur simultaneously in outbreaks. This study recommends enhanced training of physicians on the differential diagnosis of typhus and typhoid fever to reduce the misdiagnosis. In addition, laboratories need to upgrade their diagnostic protocols and capacity to use blood cultures to diagnose typhoid fever.

Malaria Infection in Thapangthong District, Savannakhet Province, Lao PDR, 2025: Bed Net Use and Forest Visit

Wed, 31 Dec 2025 00:00:00 +0700

On 19 Mar 2025, four Plasmodium vivax cases were reported in Thapangthong District, Savannakhet Province—an area previously considered malaria-free in Lao People’s Democratic Republic (Lao PDR). The investigation was conducted from
20–28 Apr 2025. We aimed to confirm the outbreak, describe characteristics of the cases, identify associated factors, and recommend containment measures. We reviewed District Health Information Software Version 2 (DHIS2)—a national surveillance system for public facilities of Lao PDR. An active case finding was conducted in three villages in Thapangthong District. Univariable and multivariable logistic regression models were performed. Qualitative phone interviews with key stakeholders were conducted. From January to April 2025, eight confirmed malaria cases were detected based on DHIS2. Of the 294 screened individuals, 20 P. vivax cases (12 suspected and 8 confirmed) were identified. Multivariable analysis showed that prior malaria infection and recent travel history to endemic areas were significantly associated with increased odds of infection. Use of long-lasting insecticide-treated nets (LLIN) was associated with a non-significant but lower odds of infection. All participants with a history of forest visits were cases. The interviews revealed that a malaria control barrier included low usage of LLIN by the villagers. Rapid interventions, including a mass drug campaign, were implemented. As of 31 May 2025, no new cases had been detected. To advance malaria elimination, we recommend strengthening campaigns that promote LLIN usage, particularly among forest-goers, providing refresher courses on malaria-related knowledge for villagers and health volunteers, and maintaining active vigilance for new cases.

High Usability but Limited Case Capture: Performance of Thailand’s Digital Influenza Surveillance System in a Private Hospital Setting

Wed, 31 Dec 2025 00:00:00 +0700

The Digital Disease Surveillance (DDS) system was introduced in 2024 to enhance real-time monitoring of influenza. However, there has been no performance assessment among private hospitals that have adopted this system. This study assessed the performance of the DDS for influenza surveillance at a private hospital in Thailand. We conducted a mixed-methods study from January to December 2024. We analyzed data from the Hospital Information System, DDS and interviewed 23 stakeholders. We assessed system attributes, including sensitivity, positive predictive value (PPV), completeness, accuracy, timeliness, and representativeness. Qualitative findings indicated high system simplicity and usability, with data outputs utilized for hospital-level resource preparation and vaccination campaign planning. Quantitative attributes of 250 reported-cases showed a high PPV (82% for the Division of Epidemiology (DOE) case definition and 100% for physician diagnosis and laboratory-based definitions), 100% data completeness, and 89% timeliness (reporting within 7 days). A critical limitation in system automation was identified, notably incorrect data extraction via an application programming interface (API) necessitated a reliance on manual data entry. This contributed to a low sensitivity (535/5,751: 9%), particularly using the DOE definition, compared to physician diagnosis (622/1,776: 35%) and laboratory-based definitions (723/1,746: 41%). This low sensitivity was attributable to systematic exclusion of outpatients and non-local residents. While the DDS demonstrates high usability and data quality for reported-cases, its reliance on manual workflows due to API failure results in low sensitivity. These gaps limit its effectiveness for comprehensive surveillance. Enhancing API integration, revising case definitions, and standardizing reporting protocols are recommended.

Investigation of an Influenza A(H3N2) Outbreak and Assessment of Vaccine Effectiveness at a Non-commissioned Officer Training Center, Saraburi Province, Thailand, 2025

Panupong Tantirat, Sitthanon Jamhom, Jiraporn Kruksomrong — Wed, 31 Dec 2025 00:00:00 +0700

On 13 Oct 2025, an influenza-like illness (ILI) outbreak was reported at a non-commissioned officer training center in Saraburi Province, Thailand. We investigated to verify the outbreak, describe epidemiological characteristics, identify risk factors and the causative agent, estimate vaccine effectiveness (VE), and implement control measures. We conducted a retrospective cohort study among 903 students and staff. A suspected case was defined by fever (body temperature ≥37.5 °C) or a history of fever, plus cough and at least one other related symptom (sore throat, rhinorrhea, myalgia, headache, fatigue, or dyspnea), with onset between 1–28 Oct 2025. Data were collected via an online questionnaire, and specimens were tested using real-time PCR. Poisson regression with robust error variance estimated adjusted risk ratios (ARR). Of 887 respondents (98.2%), 159 suspected cases (attack rate 17.9%) were identified. Influenza A(H3N2) was confirmed. The epidemic curve, peaking on 11 Oct 2025, was consistent with person-to-person transmission, and the basic reproduction number was estimated at 0.81–1.10. Significant risk factors included close contact with a patient (ARR 1.22; 95% confidence interval (CI) 1.06–1.42) and sharing personal items (ARR 1.20; 95% CI 1.06–1.36). Handwashing before meals was protective (ARR 0.80; 95% CI 0.72–0.89). The VE against clinical illness was 19.1% (95% CI -20.0%–43.9%). This outbreak was associated with personal hygiene-related risk factors. The VE was low and not statistically significant, which may be consistent with known vaccine limitations against A(H3N2) strains. The outbreak rapidly subsided following the implementation of public health control measures.

A Food Poisoning Outbreak in a School from Progressive Contamination of Norovirus, Amnat Charoen Province, Thailand, February 2025

Wed, 31 Dec 2025 00:00:00 +0700

On 13 Feb 2025, students and staff at School A in Hua Taphan District, Amnat Charoen Province, Thailand, developed gastroenteritis symptoms. An investigation was conducted to confirm the diagnosis, describe outbreak characteristics, identify possible sources and risk factors, and provide recommendations. A suspected case was an individual present at the school between 11–24 Feb 2025 who experienced three or more loose or liquid stools within 24 hours or at least one episode of vomiting. Data was collected via questionnaires and hospital records. Rectal swabs and stool samples were tested, and the environment was assessed. A retrospective cohort study was conducted using multivariable Poisson regression with robust error variance to calculate adjusted relative risks (ARR). The attack rate was 30.2% (142/470). Common symptoms were nausea (85%), abdominal pain (79%), and vomiting (76%). The epidemic curve indicated a point-source exposure followed by secondary transmission. Norovirus was detected in 71.4% of clinical samples, including one asymptomatic food handler. The chicken rice meal served on 11 February, had the highest ARR of 4.37 (95% confidence interval (CI) 1.12–17.10). Students served later (grades 4–6) had a significantly higher risk compared to the early serving group (ARR 2.17, 95% CI 1.37–3.43), suggesting progressive contamination. The epidemiological and laboratory results suggested that the chicken rice meal, was likely contaminated by an infected asymptomatic food handler, which was the source of the norovirus outbreak. The study recommendations included improving food-handling practices, strengthening hand hygiene infrastructure, and ensuring regular maintenance of the water treatment system.

A Design Thinking Approach to Developing an Innovative Board Game for Preventing Leptospirosis among Schoolchildren in Nan Province, Thailand

Patcharin Tantiworrawit, Panithee Thammavijaya — Wed, 31 Dec 2025 00:00:00 +0700

Leptospirosis is a major public health concern in Thailand. In 2024, Nan Province reported an increasing incidence of leptospirosis cases, with schoolchildren accounting for the majority, including one fatality. Entertainment-education is an effective public health communication strategy for school-aged populations, improving both understanding and engagement. This study applied a design-thinking approach to develop an innovative game-based intervention and assess its effectiveness in enhancing awareness, knowledge, and preventive practices related to leptospirosis among schoolchildren. The study employed a mixed-methods research and development design, conducted between January and September 2025. Qualitative methods were used to identify schoolchildren’s needs and contexts, which informed the development of the Lepto Game, an interactive simulation board game. A quantitative one-group pre-post design was used to evaluate the intervention’s effectiveness. Three main issues were identified: (1) limited communication between schoolchildren and healthcare providers about the disease and its symptoms, (2) low general awareness of leptospirosis, and (3) the need for more engaging and enjoyable health education tools. Among 132 schoolchildren who tested the intervention, satisfaction with learning was very high. In the quantitative study (n=124, 68.5% male, age 12–15 years), significant improvements were observed in mean scores for knowledge of exposure risks (0.395), symptoms (0.387), and self-care practices (0.556). Integrating design thinking with entertainment-education can create engaging interventions that effectively enhance awareness, knowledge, and preventive practices among schoolchildren.

Uttar Tolarbagh Model—an Investigation of a COVID-19 Case Led to the First Localized Community Approach for Containment of COVID-19 in Dhaka City, Bangladesh, March–May 2020

Wed, 31 Dec 2025 00:00:00 +0700

On 23 Mar 2020, Uttar Tolarbagh, a two-square-kilometer walled-in area in Dhaka, was locked down to contain a COVID-19 outbreak. We evaluated whether localized restrictions on entry and exit points could prevent the spread of COVID-19. We traced contacts and conducted active surveillance from 20 Mar to 10 Apr 2020. Contacts were those within one meter of a confirmed COVID-19 case for ≥15 minutes between two days before and 14 days after the onset of symptoms. We collected swabs from all persons with respiratory symptoms. The positivity rate was calculated by dividing the number of positive samples by the total number of samples tested. The Uttar Tolarbagh House, Flat Owners’ Association and the religious teacher of Masjidul Ahsan, the only mosque in Uttar Tolarbagh, discouraged local gatherings and ensured social distancing during mosque prayers. We identified 400 contacts; 156 were symptomatic and 16 tested positive, of whom eight were hospitalized and two died. SARS-CoV-2 PCR positivity rates among symptomatic contacts were 40% (2/5) before containment, 10% (15/152) during containment, and 0% (0/33) after containment. The last case’s disease onset date was 5 April, and Uttar Tolarbagh remained COVID-19 free until 12 May 2020. Social distancing was observed by the field investigation team on the roads and within the mosque during the lockdown. Our findings suggest that the neighborhood lockdown, isolation of cases, quarantine and contact tracing, evacuation of COVID-19 patients, and community engagement helped to contain COVID-19 transmission in a densely populated area of Dhaka City.

Mass Psychogenic Illness in a School during a Human Papillomavirus Vaccination Campaign, Bangladesh, 2024

Jafrin Jahed Jiti, Dr.Shahabuddin Manik, Alden Henderson — Wed, 31 Dec 2025 00:00:00 +0700

Mass psychogenic illness (MPI) poses a public health threat due to rapid spread, diagnostic difficulty, and potential to undermine public trust. Effective prevention and response require recognition of social and psychological risk factors with clear communication, education, and preparedness. On 30 Oct 2024, two students at a school in Gobindaganj, Bangladesh developed symptoms such as shortness of breath, abdominal cramps, and body aches shortly after receiving the human papillomavirus (HPV) vaccine. Within hours, 17 more reported similar symptoms. This investigation describes the outbreak by person, place, and time, documents the response by health authorities and hospital staff, and outlines measures taken to maintain confidence in HPV vaccine safety. Health officials reviewed hospital records, interviewed students, teachers, vaccinators, and health officials, and evaluated vaccine storage and cold chain integrity. Among 80 vaccinated students, 19 developed symptoms, resulting in an attack rate of 24%. Five students were hospitalized, three had hypokalemia linked to hyperventilation. All fully recovered within 24 hours. No evidence was found of vaccine quality issues, cold chain failures, immunization errors, infectious causes, or environmental exposures. The symptom pattern, rapid spread, absence of an organic cause, and presence of psychological stressors led to classification of the event as MPI. Management focused on symptomatic care, reassurance about vaccine safety, and real-time public and media communication. Authorities also addressed vaccine misinformation through press briefings, community outreach, and engagement with religious leaders. This incident highlights the need to integrate MPI preparedness into immunization campaign planning to ensure rapid containment and sustained public trust.

The Grammar of Science: The Challenge of Competing Outcomes

Jaranit Kaewkungwal — Wed, 31 Dec 2025 00:00:00 +0700