The Natural History and Transmission Potential of Asymptomatic Severe Acute Respiratory Syndrome Coronavirus 2 Infection
Nguyễn Văn Vĩnh Châu, Vo Thanh Lam, Nguyen Thanh Dung, Lam Minh Yen, Ngo Ngọc Quang Minh, Le Manh Hung, Nghiêm My Ngoc, Nguyen Tri Dung, Dinh Nguyen Huy Man, Lam Anh Nguyet, Le Thanh Hoang Nhat, Le Nguyen Truc Nhu, Nguyen Thi Han Ny, Nguyen Thi Thu Hong, Evelyne Kestelyn, Nguyễn Thị Phương Dung, Tran Chanh Xuan, Tran Tinh Hien, Nguyễn Thanh Phong, Tran Nguyen Hoang Tu, Ronald B. Geskus, Tran Tan Thanh, Nguyen Thanh Truong, Nguyen Tan Binh, Tang Chi Thuong, Guy Thwaites, Le Van Tan, Nguyễn Văn Vĩnh Châu, Nguyen Thanh Dung, Le Manh Hung, Huỳnh Thị Loan, Nguyen Thanh Truong, Nguyễn Thanh Phong, Dinh Nguyen Huy Man, Nguyễn Văn Hảo, Duong Bich Thuy, Nghiêm My Ngoc, Nguyen Phu Huong Lan, Pham Thi Ngoc Thoa, Tran Nguyen Phuong Thao, Tran Thi Lan Phuong, Le Thi Tam Uyen, Tran Thi Thanh Tam, Bui Thi Ton That, Huynh Kim Nhung, Ngo Tan Tai, Tran Nguyen Hoang Tu, Vo Trong Vuong, Dinh Thi Bich Ty, Le Thi Dung, Thai Lam Uyen, Nguyen Thi My Tien, Ho Thi Thu Thao, Nguyen Ngoc Thao, Huynh Ngoc Thien Vuong, Pham Ngoc Phuong Thao, Phan Minh Phuong, Dong Thi Hoai Tam, Evelyne Kestelyn, Joseph Donovan, Ronald B. Geskus, Guy Thwaites, H. Rogier van Doorn, Ho Van Hien, Huynh Le Anh Huy, Huynh Ngan Ha, Huynh Xuan Yen, Jennifer Ilo Van Nuil, Jeremy Day, Joseph Donovan, Katrina Lawson, Lam Anh Nguyet, Lam Minh Yen, Le Nguyen Truc Nhu, Le Thanh Hoang Nhat, Le Van Tan, Sonia Lewycka Odette, Louise Thwaites, Maia A. Rabaa, Marc Choisy, Mary Chambers, Motiur Rahman, Ngô Thị Hoa, Nguyễn Thanh Thùy Nhiên, Nguyen Thi Han Ny, Nguyen Thi Kim Tuyen, Nguyễn Thị Phương Dung, Nguyen Thi Thu Hong, Nguyen Xuan Truong, Phan Nguyen Quoc Khanh, Phung Le Kim Yen, Sophie Yacoub, Thomas Kesteman, Nguyễn Thụy Thương Thương, Tran Tan Thanh, Tran Tinh Hien, Vu Thi Ty Hang, Nguyen Tri Dung, Le Hong Nga
Abstract
BACKGROUND: Little is known about the natural history of asymptomatic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. METHODS: We conducted a prospective study at a quarantine center for coronavirus disease 2019 in Ho Chi Minh City, Vietnam. We enrolled quarantined people with reverse-transcription polymerase chain reaction (RT-PCR)-confirmed SARS-CoV-2 infection, collecting clinical data, travel and contact history, and saliva at enrollment and daily nasopharyngeal/throat swabs (NTSs) for RT-PCR testing. We compared the natural history and transmission potential of asymptomatic and symptomatic individuals. RESULTS: Between 10 March and 4 April 2020, 14 000 quarantined people were tested for SARS-CoV-2; 49 were positive. Of these, 30 participated in the study: 13 (43%) never had symptoms and 17 (57%) were symptomatic. Seventeen (57%) participants imported cases. Compared with symptomatic individuals, asymptomatic people were less likely to have detectable SARS-CoV-2 in NTS collected at enrollment (8/13 [62%] vs 17/17 [100%]; P = .02). SARS-CoV-2 RNA was detected in 20 of 27 (74%) available saliva samples (7 of 11 [64%] in the asymptomatic group and 13 of 16 [81%] in the symptomatic group; P = .56). Analysis of RT-PCR positivity probability showed that asymptomatic participants had faster viral clearance than symptomatic participants (P < .001 for difference over the first 19 days). This difference was most pronounced during the first week of follow-up. Two of the asymptomatic individuals appeared to transmit SARS-CoV-2 to 4 contacts. CONCLUSIONS: Asymptomatic SARS-CoV-2 infection is common and can be detected by analysis of saliva or NTSs. The NTS viral loads fall faster in asymptomatic individuals, but these individuals appear able to transmit the virus to others.