Outbreak, Surveillance, Investigation & Response (OSIR) Journal

Predicting Factors for Malaria Reintroduction and A Multi-factorial Approach to Prevent Malaria Outbreaks in the Malaria-free Areas

Darin Areechokchai — Tue, 24 Sep 2024 00:00:00 +0700

Thailand’s National Malaria Elimination Strategy, 2017–2026, aims to reach zero indigenous transmission by 2024. During 2016–2021, Thailand had successfully reduced its malaria burden by more than 80%. However, a resurgence of malaria in 2022 saw an increase in the incidence in 33 provinces. To identify the predictors of malaria epidemic re-occurring in malaria-free areas, secondary data of malaria-reintroduced villages in 2022 were obtained from the Malaria Information System. A descriptive cross-sectional study was conducted to compare characteristics, prevention, and response measures between villages with and without sustained local transmission after malaria reintroduction. A retrospective cohort study was conducted to determine the associations between sustained local transmission and potential predictors. Among the transmission foci in 2022, 336 villages had previously been malaria-free, of which 73 (21.7%) reported sustained local transmission. A multi-level logistic regression model, considering villages clustered within provinces, found that villages located in a district which contained active foci (adjusted odds ratio (AOR) 1.03, 95% confidence interval (CI) 1.01–1.05) and having a higher proportion of non-Thai cases (AOR 12.3, 95% CI 5.69–26.6) were significantly associated with sustained local transmission whereas coverage of malaria control within 7 days was protective (AOR 0.20, 95% CI 0.09–0.44). Areas with high migrant populations were associated with a higher risk of malaria reintroduction. Proactive case search should target these populations to quickly detect reintroduced cases and conduct timely control to prevent further local transmission.

Addressing Pertussis Outbreaks in the Deep South of Thailand, 2024: a Comparative Cost-effectiveness Study of Various Vaccination Coverage Strategies

Tue, 24 Sep 2024 00:00:00 +0700

Pertussis outbreaks continue to challenge public health efforts in the Deep South of Thailand. Low vaccination coverage is among many key contributory factors. The objective of this study is to explore policy alternatives aiming to expand vaccination coverage in Thailand’s Deep South. We applied a compartmental model alongside rapid cost-effectiveness analysis to examine how different vaccination strategies impact pertussis cases and associated costs. Four vaccination scenarios with varying coverage levels (ranging from 62% to 91% within a 120-day timeframe) were compared against a scenario with the baseline vaccine coverage (61%). With a reproduction number (R₀) of five, the model predicted a remarkable decrease in pertussis cases and fatalities as the vaccination coverage increases. All scenarios yielded cost-saving outcomes, with the scenario of an increase of 10% coverage being the most cost-effective relative to the status quo. However, in high epidemic states (R₀=6), the scenario of an increase of 30% coverage was the most optimal for cost-saving in deaths prevention. These results highlight the need for expedite vaccine roll-out and the integration of non-pharmaceutical interventions for pertussis control. Further studies that explore various aspects of the model while incorporating more intricate parameters are recommended.

An Investigation of a Community Chickenpox Outbreak with a Fatal Case, Songkhla Province, Thailand, October 2022

Tue, 24 Sep 2024 00:00:00 +0700

In October 2022, a suspected chickenpox death was notified. A field investigation was done to verify the diagnosis and cause of death, describe the epidemiological characteristics, identify risk factors, and control the outbreak. We conducted a descriptive study and a matched case-control study. A case was defined as a person with multiple stages of skin lesions on at least two body areas in Subdistrict from 1 Aug 2022 to 24 Oct 2022. We reviewed medical records and searched for cases house-to-house. For the matched case-control study, cases were chickenpox cases residing in Bo Tru Subdistrict, from 1 Aug 2022 to 14 Oct 2022. Controls were neighbors without symptoms or chickenpox history, matched by age. Samples were tested using the reverse transcription polymerase chain reaction technique. Environmental surveys were performed. We identified 30 cases including the deceased, who was 49 years old. The median (interquartile range) age of the cases was 11 (7–38) years. Seventeen were elementary-school students. None of the cases received chickenpox vaccination or had a history of chickenpox. The secondary attack rate among household contacts was 41.2% (14/34). Reverse transcriptase polymerase chain reaction tests from three cases were all positive. Being a close contact with a case and sharing personal utensils were risk factors. We strengthened the surveillance system for early detection and treatment and provided risk communication in the community. Chickenpox cases should be isolated from susceptible persons. Standard treatment guidelines for complicated cases should be distributed among healthcare services.

Accuracy of COVID-19 Prediction Modeling Techniques

Panithee Thammawijaya, Rapeepong Suphanchaimat — Tue, 24 Sep 2024 00:00:00 +0700

The unprecedented impact of the COVID-19 pandemic has revealed that forecasting capability is critically needed in making strategic decisions and formulating reasonable countermeasures. This study aimed to assess the predictive accuracy in forecasting the numbers of COVID-19 cases using Thailand’s national COVID-19 surveillance database from January 2020– June 2021 based on three analytical models: a susceptible-exposed-infectious-recovery compartmental model, an auto-regressive integrated moving average model, and a long short-term memory (LSTM) network model. All forecasting methods had model parameters adjusted weekly according to the most recent situation and predictive accuracy measures, including the mean absolute percentage error (MAPE). We found that the MAPE values ranged from 19.65%–22.54%, 28.95%–32.35%, 47.78%–53.55%, and 75.03–84.91% for forecasting one, two, four, and eight weeks ahead, respectively. Among the three models, the LSTM model had slightly higher accuracy than the other two models within the same forecasting range. These prediction models can be used for short-range forecasts in other similar settings while long-range forecasting requires monitoring and updating periodically.

Effectiveness and Safety of Long-acting Antibody (LAAB) to Prevent COVID-19 among High-risk Population in Thailand: a 6-month Retro-prospective Cohort Study

Tue, 24 Sep 2024 00:00:00 +0700

During COVID-19 pandemic, evidence showed lower immunity after infection and vaccination among immunocompromised individuals. In July 2022, a prophylaxis campaign using long-acting antibodies (LAAB), tixagevimab-cilgavimab was launched in Thailand to decrease hospitalizations among high-risk groups. To evaluate the real-world effectiveness and safety of LAAB for high-risk populations, a 6-month retro-prospective cohort study was conducted starting in March 2023. We included 1,249 participants aged ≥18 years with high-risk conditions who tested negative for COVID-19 using antigen test kits during the campaign in Thailand’s central, northern, and northeastern regions. Participants provided blood samples for anti-S and anti-N IgG testing and were monitored weekly by phone for six months for acute respiratory symptoms and were screened if COVID-19 was suspected. Positive cases were further tested with RT-PCR and sequencing. We matched 600 individuals who received the study drug tixagevimab-cilgavimab (exposed) by age and comorbidities to 600 individuals who did not receive the drug (non-exposed). Predominant strain was the omicron sublineage XBB. One participant who did not receive the drug was hospitalized without respiratory failure. Anti-N IgG was positive and high levels of anti-S IgG were observed. The effectiveness of tixagevimab-cilgavimab in preventing COVID-19 infections or hospitalizations among high-risk groups was not seen. Existing immunity from previous infections and vaccinations likely influenced these results. No serious adverse events related to the drug were reported. Despite these findings, there is a potential prophylactic role of LAAB for immunocompromised groups in the early phase of a pandemic while effective vaccines and treatments are unavailable.

The Grammar of Science: It’s All about Trustworthiness of Your Data

Jaranit Kaewkungwal — Tue, 24 Sep 2024 00:00:00 +0700