Abstract
Non-healthcare workers with a high potential for exposure to severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) may contribute to the virus spreading. Data among asymptomatic and high exposure risk populations is still scarce, in particular Chiang Mai and Lamphun provinces, Thailand. We conducted a cross-sectional observational study aiming to assess the prevalence of SARS-CoV-2 RNA positivity, anti-SARS-CoV-2 IgM/IgG, and potential associated factors among asymptomatic/mild symptomatic individuals with a high exposure risk in Chiang Mai and Lamphun provinces, during the second wave of outbreak in Thailand (November 2020–January 2021). Socio-demographic data was collected through an on-line questionnaire prior to collection of nasopharyngeal/throat swab samples and blood samples tested for SARS-CoV-2 RNA (DaAn Gene, China) and anti-SARS-CoV-2 IgM/IgG antibodies (commercial lateral flow immunoassays), respectively. Univariable and multivariable logistic regression analysis were used to analyze associated factors. None of 1,651 participants were found positive for SARS-CoV-2 RNA (0%, 95% confidence intervals, CI: 0–0.2). Fourteen were positive for anti-SARS-CoV-2 IgM/IgG antibodies (0.9%, 95% CI: 0.5–1.4), including 7 positives for IgM and 7 positives for IgG (0.4%, 95% CI: 0.2–0.9). Being over 50 years old was independently associated with virus exposure (OR: 5.8, 95% CI: 1.0–32.1%, p = 0.045). Despite high exposure risk, no current infection was found, and a very high proportion was still susceptible to SARS-CoV-2 infection and would clearly benefit from vaccination. Continuing active surveillance, rolling out of vaccination and monitoring response to vaccine will help better control the COVID-19 spread.
Highlights
The emergence of a new human coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), in late 2019 has sparked an explosive global pandemic of Coronavirus Disease 2019 (COVID-19) [1, 2]
The at-risk populations in this study included individuals who were at-risk to expose to SARS-CoV-2 infection, which may relate to their behaviors, household being, or occupations
During November 2020–January 2021, we found no active SARS-CoV-2 infection among atrisk populations living in Chiang Mai and Lamphun provinces, and a seroprevalence of antiSARS-CoV-2 IgM/IgG antibodies of 0.9%
Summary
The emergence of a new human coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), in late 2019 has sparked an explosive global pandemic of Coronavirus Disease 2019 (COVID-19) [1, 2]. Manifestations of COVID-19 vary from asymptomatic to fatal. The proportions of asymptomatic individuals ranged between 20–75% among COVID-19 cases according to different study groups, countries and the mean age of studied population [4, 5]. Some cases may develop an acute respiratory distress syndrome (ARDS), shock, and multiple organ failure leading to death [6, 7]. The majority of deaths occurred mostly in elderly people aged over 60 years old and people with underlying diseases such as cardiovascular disease, diabetes mellitus, hypertension and malignancy [9]
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