Background COVID-19 seroprevalence data, particularly in less developed countries with a relatively low incidence, has been scant. We aimed to explore the seroprevalence of hospital staff in the area with zero confirmed COVID-19 case to shed light on the situation of COVID-19 infection in zero or low infection rate countries where mass screening was not readily available. Methods A locally developed rapid immunoglobulin M (IgM)/immunoglobulin G (IgG) test kit was used for hospital staff screening of Ranong hospital which is located in a province with zero COVID-19 prevalence in Thailand from 17th April to 17th May 2020. All staff was tested, 100 of which were randomly invited to have a repeating antibody test in one month. (Thai Clinical Trials Registry: TCTR20200426002) Results Of 844 hospital staff, 82 were tested twice one month apart (response rate for repeating antibody test 82%). Overall, 0.8% of the participants (7 of 844) had positive IgM, none had positive IgG. Female staff had 1.0% positive IgM (95% CI: 0.5–2.1%) while male had 0.5% positive IgM (95% CI: 0.1–2.6%). No participants with a history of travel to the high-risk area or close contact with PCR-confirmed COVID-19 case developed SARS-CoV-2 antibodies. Among 844 staff, 811 had no symptoms and six of them developed IgM seropositive (0.7%) while 33 had minor symptoms and only one of them developed IgM seropositive (3.0%). No association between SARS-CoV-2 IgM status and gender, history of travel to a high-risk area, close contact with PCR-confirmed or suspected COVID-19 case, presence of symptoms within 14 days, or previous PCR status was found. None of the hospital staff developed SARS-CoV-2 IgG. Conclusions COVID-19 antibody test could detect a considerable number of hospital staff who could be potential silent spreaders in a province with zero COVID-19 cases. Accurate antibody testing is a valuable screening tool, particularly in asymptomatic healthcare workers. Trial registration: This study was approved by the Institutional Review Board of Chulalongkorn University (IRB No.236/63) and the Institutional Review Board of Ranong Hospital. (Thai Clinical Trials Registry: TCTR20200426002).

Introduction Coronavirus disease 2019 (COVID-19) pandemic has affected the aviation industry. Existing protocols have relied on scientifically questionable evidence and might not lead to the optimal balance between public health safety and airlines' financial viability. Objective To explore the implementation feasibility of Thai Airways International protocol from the perspectives of passengers and aircrews. Design An online questionnaire survey of passengers and an in-depth interview with aircrews. Setting Two randomly selected repatriation flights operated by Thai Airways International using Boeing 777 aircraft (TG476 from Sydney and TG492 from Auckland to Bangkok) Participants 377 Thai passengers and 35 aircrews. Results The mean age of passengers was 28.14 (95%CI 26.72 to 29.55) years old; 57.03% were female. TG492 passengers were mostly students and significantly younger than that of TG476 (p<0.0001) with comparable flying experience (p = 0.1192). The average body temperature was 36.52 (95%CI 36.48 to 36.55) degrees Celsius. Passengers estimated average physical distances of 1.

Background: COVID-19 seroprevalence data has been scarce, especially in less developed countries with a relatively low infection rate. Methods: A locally developed rapid IgM/IgG test kit was used for screening hospital staff and patients who required procedural treatment or surgery in 52 hospitals in Thailand from April 8 to June 26, 2020. A total of 857 participants were tested--675 were hospital staff and 182 were pre-procedural patients. (Thai Clinical Trials Registry: TCTR20200426002) Results Overall, 5.5% of the participants (47 of 857) had positive immunoglobulin M (IgM), 0.2% (2 of 857) had positive immunoglobulin G (IgG) and IgM. Hospitals located in the Central part of Thailand had the highest IgM seroprevalence (11.9%). Preprocedural patients had a higher rate of positive IgM than the hospital staff (12.1% vs. 3.7%). Participants with present upper respiratory tract symptoms had a higher rate of positive IgM than those without (9.6% vs. 4.5%). Three quarters (80.5%, 690 of 857) of the participants were asymptomatic, of which, 31 had positive IgM (4.5%) which consisted of 20 of 566 healthcare workers (3.5%) and 11 of 124 preprocedural patients (8.9%). Conclusions COVID-19 antibody test could detect a substantial number of potential silent spreaders in Thai community hospitals. Antibody testing should be encouraged for mass screening, especially in asymptomatic individuals.

ObjectivesWe aimed to explore the seroprevalence of hospital staff comparing to preprocedural patients in Thai community hospitals to shed light on the situation of COVID-19 infection of frontline healthcare workers in low infection rate countries where mass screening was not readily available.DesignCross-sectional study.Setting52 community hospitals in 35 provinces covered all regions of Thailand.Participants857 participants consisted of 675 hospital staff and 182 preprocedural patients.Outcome measureCOVID-19 seroprevalence using a locally developed rapid IgM/IgG test kitResultsOverall, 5.5% of the participants (47 of 857) had positive IgM, 0.2% (2 of 857) had positive IgG which both of them also had positive IgM. Hospitals located in the central part of Thailand had the highest IgM seroprevalence (11.9%). Preprocedural patients had a higher rate of positive IgM than the hospital staff (12.1% vs 3.7%). Participants with present upper respiratory tract symptoms had a higher rate of positive IgM than those without (9.6% vs 4.5%). Three quarters (80.5%, 690 of 857) of the participants were asymptomatic, of which, 31 had positive IgM (4.5%) which consisted of 20 of 566 healthcare workers (3.5%) and 11 of 124 preprocedural patients (8.9%).ConclusionsCOVID-19 antibody test could detect a substantial number of potential silent spreaders in Thai community hospitals where the nasopharyngeal PCR was not readily available, and the antigen test was prohibited. Antibody testing should be encouraged for mass screening in a limited resource setting, especially in asymptomatic individuals.Trial registrationTCTR20200426002.

BACKGROUND. COVID-19 seroprevalence data has been scarce, especially in less developed countries with a relatively low infection rate. METHODS. A locally developed rapid IgM/IgG test kit was used for screening hospital staff in Ranong hospital which located in a province with zero COVID-19 prevalence in Thailand from April 17 to May 17, 2020. A total of 844 participants were tested; 82 of which were tested twice with one month apart. (Thai Clinical Trials Registry: TCTR20200426002) RESULTS. Overall, 0.8% of the participants (7 of 844) had positive immunoglobulin M (IgM), none had positive immunoglobulin G (IgG). Female staffs seemed to have higher IgM seropositive than male staffs (1.0% vs. 0.5%). None of the participants with a history of travel to the high-risk area or a history of close contact with PCR-confirmed COVID-19 case had developed antibodies against SARS-CoV-2. Among 844 staff, 811 had no symptom and six of them developed IgM seropositive (0.7%) while 33 had minor symptoms and only one of them developed IgM seropositive (3.0%). No association between IgM antibody against SARS-CoV-2 status and gender, history of travel to a high-risk area, history of close contact with PCR-confirmed COVID-19 case, history of close contact with suspected COVID-19 case, presence of symptoms within 14 days, or previous PCR status was found. None of the hospital staff developed IgG against SARS-CoV-2. CONCLUSION. COVID-19 antibody test could detect a substantial number of hospital staffs who could be potential silent spreaders in a province with zero COVID-19 case. Antibody testing should be encouraged for mass screening, especially in asymptomatic healthcare workers.