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Low Seroprevalence of COVID-19 in Lao PDR, Late 2020

23 Pages Posted: 19 Apr 2021

See all articles by Siriphone Virachith

Siriphone Virachith

Institut Pasteur du Laos

Virginie Pommelet

Institut Pasteur du Laos

Elodie Calvez

Institut Pasteur du Laos

Vilaysone Khounvisith

Institut Pasteur du Laos

Somphou Sayasone

Lao Tropical Public Health Institute

Sengchanh Kounnavong

Lao Tropical Public Health Institute

Mayfong Maxay

Mahosot Hospital - Lao-Oxford-Mahosot Hospital-Wellcome Trust Research Unit

Phonepadith Xangsayarath

National Centre for Laboratory and Epidemiology

Sarah Temmam

University of Paris-Saclay - Pathogen Discovery Laboratory

Marc Eloit

University of Paris-Saclay - Pathogen Discovery Laboratory; Ecole Nationale Vétérinaire d'Alfort

Nicolas Escriou

Institut Pasteur du Laos

Thierry Rose

Institut Pasteur du Laos

Khamsing Vongphayltoh

Institut Pasteur du Laos

Judith M. Hübschen

Luxembourg Institute of Health (LIH)

Vincent Lacoste

Institut Pasteur du Laos

Somphavanh Somlor

Institut Pasteur du Laos

Darouny Phonekeo

Institut Pasteur du Laos

Paul Brey

Institut Pasteur du Laos

Antony Paul Black

Institut Pasteur du Laos

More...

Abstract

Background: Lao PDR has low reported COVID-19 cases but it is unclear whether this masks silent transmission. A nationwide seroprevalence study was done between August and September 2020 to determine SARS-CoV-2 exposure.

Methods: Participants were from the general community/healthcare workers in five provinces. Bat/wildlife contacts were from Vientiane province. ELISAs detected anti-Nucleoprotein (N; n=3173 tested) and anti-Spike (S; n=1417 tested) SARS-CoV-2 antibodies. Double-positive samples were checked by IgM/IgG rapid tests. Positive controls were confirmed COVID-19 cases and negative controls were pre-COVID-19 samples.

Findings: In pre-COVID-19 samples, 14/265 (5·3%, [95% CI=3·1-8·7%]) were anti-N antibody single-positive and 3/265 (1·1% [0·3-3·5%]) were anti-S antibody single positive. None were anti-N and anti-S antibody double positive. Anti-N and anti-S antibodies were detected in 131/2417 (5·4% [4·5-6·3%]) and 19/1061 (1·8% [1·1-2·8%]) of the general population, 13/666 (2·0% [1·1-3·3%]) and 4/282 (1·4% [0·5-3·7%]) of healthcare workers and 15/74 (20·3% [12·6-31·0%]) and 5/74 (6·8% [2·8-15·3%]) of bat/wildlife contacts. Only 2/3173 (0·1% [0·02-0·3%]) were double positive for anti-N and anti-S antibodies (rapid test negative).

Interpretation: We find no evidence for significant circulation of SARS-CoV-2 in Lao PDR during or before September 2020. This likely results from decisive measures taken by the government early in the pandemic, social behavior, and low population density. High anti-N antibodies/low anti-S antibodies in bat/wildlife contacts may indicate exposure to cross-reactive animal coronaviruses with threat of emerging novel viruses.

Funding: Core; Agence Française de Développement. Additional support; Institut Pasteur du Laos, Institute Pasteur, Paris and Luxembourg Ministry of Foreign and European Affairs (“PaReCIDS II”).

Declaration of Interests: The authors have no conflict of interest to declare.

Ethics Approval Statement: The study protocol was approved by all participating institutes and by the Lao National Ethics Committee for Health Research (NECHR) (Ref #052/2020).

Suggested Citation

Virachith, Siriphone and Pommelet, Virginie and Calvez, Elodie and Khounvisith, Vilaysone and Sayasone, Somphou and Kounnavong, Sengchanh and Maxay, Mayfong and Xangsayarath, Phonepadith and Temmam, Sarah and Eloit, Marc and Escriou, Nicolas and Rose, Thierry and Vongphayltoh, Khamsing and Hübschen, Judith M. and Lacoste, Vincent and Somlor, Somphavanh and Phonekeo, Darouny and Brey, Paul and Black, Antony Paul, Low Seroprevalence of COVID-19 in Lao PDR, Late 2020. Available at SSRN: https://ssrn.com/abstract=3829715 or http://dx.doi.org/10.2139/ssrn.3829715

Siriphone Virachith

Institut Pasteur du Laos ( email )

Vientiane
Laos

Virginie Pommelet

Institut Pasteur du Laos ( email )

Vientiane
Laos

Elodie Calvez

Institut Pasteur du Laos ( email )

Vientiane
Laos

Vilaysone Khounvisith

Institut Pasteur du Laos ( email )

Vientiane
Laos

Somphou Sayasone

Lao Tropical Public Health Institute ( email )

Sengchanh Kounnavong

Lao Tropical Public Health Institute ( email )

Vientiane Capital
Laos

Mayfong Maxay

Mahosot Hospital - Lao-Oxford-Mahosot Hospital-Wellcome Trust Research Unit ( email )

Vientiane
Laos

Phonepadith Xangsayarath

National Centre for Laboratory and Epidemiology ( email )

Vientiane Capital
Laos

Sarah Temmam

University of Paris-Saclay - Pathogen Discovery Laboratory

Paris
France

Marc Eloit

University of Paris-Saclay - Pathogen Discovery Laboratory ( email )

28 rue du Dr Roux
Paris, 75015
France

Ecole Nationale Vétérinaire d'Alfort

Pôle HQSA, 7, av. du général de Gaulle
94 704 Maison
Alfort Cedex
France

Nicolas Escriou

Institut Pasteur du Laos ( email )

Vientiane
Laos

Thierry Rose

Institut Pasteur du Laos ( email )

Vientiane
Laos

Khamsing Vongphayltoh

Institut Pasteur du Laos ( email )

Vientiane
Laos

Judith M. Hübschen

Luxembourg Institute of Health (LIH) ( email )

1 A-B Rue Thomas Edison
Strassen
Luxembourg

Vincent Lacoste

Institut Pasteur du Laos

Vientiane
Laos

Somphavanh Somlor

Institut Pasteur du Laos ( email )

Vientiane
Laos

Darouny Phonekeo

Institut Pasteur du Laos ( email )

Vientiane
Laos

Paul Brey

Institut Pasteur du Laos ( email )

Vientiane
Laos

Antony Paul Black (Contact Author)

Institut Pasteur du Laos ( email )

Vientiane
Laos