RACSMEI addresses the high burden of infectious diseases in low- and middle-income countries, including Cambodia, where limited surveillance and laboratory capacity often obscure etiologies and transmission dynamics. This knowledge gap hinders the design of effective prevention and control strategies.

RACSMEI will improve understanding across multiple pathogens using a multidisciplinary One Health approach. We will answer key questions on burden, ecology, transmission and population immune status to inform targeted and culturally appropriate interventions. The project combines a nationally representative One Health survey, social-science methods, and multiplex, diverse diagnostics to efficiently test for 57 priority pathogens, including zoonotic and vector-borne agents, vaccine-preventable and elimination-targeted diseases, enteric, respiratory, and environmentally transmitted pathogens and selected neglected tropical diseases and parasites relevant to Cambodia.

Mathematical modelling will reconstruct and forecast transmission dynamics and assess the potential impact of future public-health strategies. By integrating intersectoral data and innovative methods, RACSMEI will generate actionable evidence for public-health authorities, support precision One Health interventions, and help reduce disease burden in affected communities. The project also aims to ensure the transferability of methods and insights to other countries facing similar challenges.

RACSMEI is a nationwide, One Health, multi-pathogen initiative designed to generate integrated evidence for public-health decision-making in Cambodia. Beyond producing epidemiological findings, the project will establish a structured biobank and curated datasets intended to support long-term collaborative research, knowledge sharing, and evidence-informed policy. The program includes capacity building and technology transfer to strengthen national institutions and foster regional scientific leadership and international collaboration. Engagement with communities and national stakeholders is planned to facilitate future studies and promote the uptake of results in practice. Overall, RACSMEI aims to provide a scalable model for integrated infectious-disease assessment in low- and middle-income settings, creating durable infrastructure, partnerships, and decision-support resources that can be used beyond the project period.

Inclusion Criteria:

• Residency in the village for more than 6 months;
• Age between 2 and 75 years old at the time of inclusion;
• For adults: provision of written consent;
• For children aged 2-17 years: written parental consent form, verbal assent from children aged 13-17 years;

Exclusion Criteria:

• Unable to understand or consent;
• Under guardianship or deprived of liberty;
• Medical conditions that impede survey participation;
• Refusal to participate in the study.

The study population comprises approximately 10,000 participants aged 2 to 75 years, drawn from 4,160 households across Cambodia's 25 provinces. Households will be randomly selected from 104 villages to ensure a nationally representative sample that reflects the country's diverse geographic and demographic characteristics. Participants will provide detailed socio-demographic information, enabling post-stratification weighted analysis of the sample's structure by sex, age, and geographic area to facilitate the extrapolation of findings to the entire population, ensuring that the study's conclusions are broadly applicable.