Virologic Characteristics of Cases of COVID-19 in Northern Vietnam,
January -- May, 2020
Abstract
Background: Vietnam confirmed its first case of SARS-CoV-2 infection on
January 23, 2020 among travelers from Wuhan, China and experienced
several clusters of community transmission until September. Vietnam
implemented an aggressive testing, isolation, contact tracing, and
quarantine strategy in response to all laboratory-confirmed cases. We
report the results of SARS-CoV-2 testing during the first half of 2020
in northern Vietnam. Methods: From January through May, 2020, 15,650
upper respiratory specimens were collected from 14,470 suspected cases
and contacts in northern Vietnam. All were tested for SARS-CoV-2 by
real-time RT-PCR. Individuals with positive specimens were tested every
3 days until negative twice. Positive specimens from 81 individuals were
cultured. Results: Among 14,470 tested individuals, 158 (1.1%) cases of
SARS-CoV-2 infection were confirmed; 89 were imported and 69 were
associated with community transmission. Most patients (122, 77%) became
negative after two tests, with 11 and 4 still testing positive when
sampled a fourth and fifth time, respectively. Among 81 specimens with
Ct values <30, SARS-CoV-2 was isolated from 29 (36%). Seven
patients testing positive again after testing negative had Ct values
>30 and negative culture. Conclusion: Early and widespread
testing for SARS-CoV-2 in northern Vietnam identified very few cases
which, when combined with other aggressive strategies, may have
dramatically contained the epidemic. We observed rapid viral clearance
and very few positive results following clearance. Large scale molecular
diagnostic testing is a critical part of early detection and containment
of COVID-19 in Vietnam and will remain necessary until a vaccine is
widely implemented.