The Natural History and Transmission Potential of Asymptomatic Severe Acute Respiratory Syndrome Coronavirus 2 Infection
Van Vinh Chau N., Lam VT., Dung NT., Yen LM., Minh NNQ., Hung LM., Ngoc NM., Dung NT., Man DNH., Nguyet LA., Nhat LTH., Nhu LNT., Ny NTH., Hong NTT., Kestelyn E., Dung NTP., Xuan TC., Hien TT., Phong NT., Tu TNH., Geskus RB., Thanh TT., Truong NT., Binh NT., Thuong TC., Thwaites G., Van Tan L., Van Vinh Chau N., Dung NT., Hung LM., Loan HT., Truong NT., Phong NT., Man DNH., Van Hao N., Thuy DB., Ngoc NM., Lan NPH., Thoa PTN., Thao TNP., Phuong TTL., Uyen LTT., Tam TTT., That BTT., Nhung HK., Tai NT., Tu TNH., Vuong VT., Ty DTB., Dung LT., Uyen TL., Tien NTM., Thao HTT., Thao NN., Vuong HNT., Thao PNP., Phuong PM., Tam DTH., Kestelyn E., Joseph D., Geskus R., Thwaites G., van Doorn HR., Van Hien H., Huy HLA., Ha HN., Yen HX., Van Nuil J., Day J., Donovan J., Lawson K., Nguyet LA., Yen LM., Nhu LNT., Nhat LTH., Van Tan L., Odette SL., Thwaites L., Rabaa M., Choisy M., Chambers M., Rahman M., Hoa NT., Nhien NTT., Ny NTH., Tuyen NTK., Dung NTP., Hong NTT., Truong NX., Khanh PNQ., Yen PLK., Yacoub S., Kesteman T., Thuong NTT., Thanh TT., Hien TT., Hang VTT., Dung NT., Nga LH.
<jats:title>Abstract</jats:title> <jats:sec> <jats:title>Background</jats:title> <jats:p>Little is known about the natural history of asymptomatic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection.</jats:p> </jats:sec> <jats:sec> <jats:title>Methods</jats:title> <jats:p>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.</jats:p> </jats:sec> <jats:sec> <jats:title>Results</jats:title> <jats:p>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 &lt; .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.</jats:p> </jats:sec> <jats:sec> <jats:title>Conclusions</jats:title> <jats:p>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.</jats:p> </jats:sec>