SARS-CoV-2 viral dynamics of the first 1000 sequences from Vietnam and neighbouring ASEAN countries.

Objective: The regional distribution and transmissibility of existing COVID-19 variants of concern (VOC) has led to concerns about increasing transmission, given the ability of VOCs to evade immunity as breakthrough infections become more prevalent. Methods: SARS-CoV-2 genomes (n = 277) were sequenced and analysed alongside all available genomes from Vietnam and ASEAN countries to understand the phylodynamics. The observed lineages were assigned using Pangolin nomenclature, and spread patterns were investigated. Results: Between January and November 8, 2021, VOCs, including alpha (B.1.1.7), beta (B.1.351), gamma (P.1), and delta (B.1.617.2), were observed across the ASEAN countries. While alpha and delta were the major VOCs in nine ASEAN countries, delta was predominant. The alpha VOC was first reported by Singapore, beta by Malaysia, gamma by the Philippines, and delta by Singapore. Of the first 1000 genomes analysed from Vietnam, alpha and delta were the most represented, with delta being the dominant VOC from May 2021. The delta variant was introduced in early January 2021, and formed a large cluster within the representative genomes. Conclusion: Spatial and temporal monitoring of SARS-CoV-2 variants is critical to the understanding of viral phylodynamics, and will provide useful guidance to policy makers for infection prevention and control.

Low Prevalence of HEV Infection and No Associated Risk of HEV Transmission from Mother to Child among Pregnant Women in Vietnam.

Infections with HEV in low- and middle-income countries (LMICs) are associated with increased rates of preterm birth, miscarriage, and stillbirth. The aim of the present study was to investigate HEV infections in pregnant women and the possibility of mother-to-child transmission, and associated outcomes. A total of 183 pregnant women in their third trimester were recruited and followed until delivery. Anti-HEV IgG and IgM were determined via enzyme-linked immunosorbent assay (ELISA), and HEV nucleic acids were detected in stool and cord blood samples. HEV genotypes were identified by Sanger sequencing, and phylogenetic analyses were performed. Mother-to-child transmission and associated adverse outcomes were not observed. Only 2% of patients (n = 4/183) tested positive for anti-HEV IgM, and 8% (n = 14/183) tested positive for anti-HEV IgG antibodies. Cord blood (n = 150) analysis showed that there was no IgM detected, while 4% (n = 6/150) tested positive for anti-HEV IgG, which was consistent with mothers testing positive for anti-HEV IgG. Nucleic acid tests for HEV RNA yielded 2% (n = 4/183) from the serum and stool of pregnant women, and none from cord blood. The HEV isolates belonged to the genotype HEV-3a, with 99% homology with humans and 96% with pigs. No association was found between the risk of HEV infection and pregnancy outcomes or HEV transmission from mother to child. HEV-3 infections of zoonotic origin in pregnancy might have eventually resolved without complications.

High Hepatitis E virus (HEV) Positivity Among Domestic Pigs and Risk of HEV Infection of Individuals Occupationally Exposed to Pigs and Pork Meat in Hanoi, Vietnam.

BACKGROUND: Hepatitis E virus (HEV) infection can occur through consumption of undercooked pork meat or exposure to animal feces. Because there are scarce data only in developing countries, we assessed whether pigs might be a potential source of human HEV infections in Vietnam. In addition, we determined anti-HEV seroprevalences in the general population and in individuals professionally exposed to pigs and pork meat. METHODS: The study took place in Hanoi, Vietnam. Liver tissues from domestic pigs (n = 210) and serum samples obtained from individuals occupationally exposed to pigs and pork meat (n = 283) and from unexposed healthy controls (n = 168) were screened for HEV-ribonucleic acid (RNA) by reverse-transcription polymerase chain reaction. The exposed group was divided into pork meat vendors (n = 81), pig farmers (n = 96), and slaughterers (n = 106). Serum samples were subjected to HEV immunoglobulin (Ig)G and IgM enzyme-linked immunosorbent assays. The HEV genotypes were assessed by direct sequencing, followed by phylogenetic analyses. RESULTS: Hepatitis E virus seroprevalence was higher among persons occupationally exposed to pigs/pork meat compared with unexposed individuals (anti-HEV IgM 11% vs 6%, P = .07; anti-HEV IgG 53% vs 31%, P < .0001). Positivity of anti-HEV IgG among slaughterhouse staff was 66%, followed by 51% in pig-farmers and 38% in pork meat vendors (P = .00073). A similar trend was observed for IgM positivity. Of the pig liver tissues, 26 of 210 (12.4%) were positive for HEV-RNA and assessed to be HEV genotype 3. CONCLUSIONS: Hepatitis E virus circulates in domestic pigs in Hanoi and constitutes a permanent zoonotic disease risk. The high HEV seroprevalence among occupationally exposed individuals indicates an associated risk of HEV infection.