2.1. Blood sample collection from villagers

An analytic cross‐sectional serological survey was conducted to determine coronavirus seroprevalence among villagers aged between 20 and 75 years old in 10 provinces within four regions of Thailand from November 2016 to May 2018. The study sites were purposively selected based on information from the Department of National Parks, Wildlife and Plant Conservation (DNP), Ministry of Natural Resources and Environment (MNRE) and Ministry of Public Health (MoPH). Scoping visits were conducted to determine potential study sites where the villagers’ residences were in or near areas of high bat density. In this study, study sites in 10 provinces representing the four regions of Thailand were chosen for sample and data collection (Figure 1).

Map of study provinces in Thailand and percentages of CoV seropositivity among villagers

Blood samples (5 ml) were collected from 364 participants who agreed to participate in both blood testing and questionnaire interviews for a quantitative study. The study participants were recruited based on the following criteria: (a) participants aged between 20 and 75 years old, (b) participants living in the study sites at least six months before data and sample collection, and (c) participants willing to participate in both blood testing and questionnaire interviews. Simple random sampling (SRS) was utilized to select the participants from the household registries at the local health offices in the communities. Approximately 30–35 participants from each village were included in the study. The study was conducted under the approval of Chulalongkorn University IRB and Chiang Rai Provincial Health Office (No. 034.1/59, No. 208.1/60 and 26/2559). Written informed consent forms were obtained from the participants before the interviews and blood collection.