Emergence of chikungunya in Moonlapamok and Khong Districts, Champassak Province, the Lao People’s Democratic Republic, May to September 2012

Introduction: Chikungunya is a vector-borne disease transmitted to humans by Aedes mosquitoes, which are widespread in the Lao People’s Democratic Republic. However, chikungunya virus (CHIKV) had not been detected in the country before outbreaks reported in July 2012. The first outbreaks were detected through health care worker event-based surveillance. Methods: The case definition for the outbreaks was defined as a person with acute onset of fever (> 38 °C) and severe arthralgia (joint pain) or arthritis from 1 May 2012 in Champassak Province. Rapid response teams conducted active case finding, performed an environmental assessment including an entomological survey and implemented control measures. Descriptive analysis was undertaken in Microsoft Excel. Results: There were 197 cases (attack rate 3.4%) of suspected chikungunya reported from 10 villages in Moonlapamok and Khong Districts of Champassak Province. All age groups (age range: seven months–74 years) were affected with slightly more female (56%) than male cases. Thirty-one per cent (16 of 52) of serum samples tested positive for CHIKV by polymerase chain reaction. The environmental assessment found poor water storage practices and high entomological indices. Discussion: These outbreaks show the effectiveness of health care worker event-based surveillance and the importance of sharing of information across borders for detecting emerging diseases. Public health education is an important measure to prevent epidemics of chikungunya. Information about chikungunya should be supplied to health care workers in the region so they are alert to the potential spread and are able to implement control measures for this disease

Bayesian spatio-temporal analysis of dengue transmission in Lao PDR

Dengue, a zoonotic viral disease transmitted by Aedes mosquitoes, poses a significant public health concern throughout the Lao People’s Democratic Republic (Lao PDR). This study aimed to describe spatial–temporal patterns and quantify the effects of environmental and climate variables on dengue transmission at the district level. The dengue data from 2015 to 2020 across 148 districts of Lao PDR were obtained from the Lao PDR National Center for Laboratory and Epidemiology (NCLE). The association between monthly dengue occurrences and environmental and climate variations was investigated using a multivariable Zero-inflated Poisson regression model developed in a Bayesian framework. The study analyzed a total of 72,471 dengue cases with an incidence rate of 174 per 100,000 population. Each year, incidence peaked from June to September and a large spike was observed in 2019. The Bayesian spatio-temporal model revealed a 9.1% decrease (95% credible interval [CrI] 8.9%, 9.2%) in dengue incidence for a 0.1 unit increase in monthly normalized difference vegetation index at a 1-month lag and a 5.7% decrease (95% CrI 5.3%, 6.2%) for a 1 cm increase in monthly precipitation at a 6-month lag. Conversely, dengue incidence increased by 43% (95% CrI 41%, 45%) for a 1 °C increase in monthly mean temperature at a 3-month lag. After accounting for covariates, the most significant high-risk spatial clusters were detected in the southern regions of Lao PDR. Probability analysis highlighted elevated trends in 45 districts, emphasizing the importance of targeted control strategies in high-risk areas. This research underscores the impact of climate and environmental factors on dengue transmission, emphasizing the need for proactive public health interventions tailored to specific contexts in Lao PDR