Detection of bovine leukemia virus in beef cattle kept in the Central Coast Regions of Vietnam.

Bovine leukemia virus (BLV) is the etiologic agent of enzootic bovine leucosis. Our previous study showed the BLV existence in cattle kept in the Red River Delta Region of Vietnam. However, no positive samples were identified in beef cattle. Besides, information related to the BLV circulation in the remained parts of Vietnam is limited. Therefore, we tested the existence of BLV in 48 beef cattle kept in the Central Coast Regions. Nested PCR targeting the BLV-env-gp51 confirmed the prevalence of 14.6% in investigated regions. Phylogenetic analysis suggested the co-existence of genotypes 1 and 10. The close relationship between strains found in Vietnam, Thailand, Myanmar, and China was revealed suggesting the possibility of BLV transmission through the movement of live cattle.

Occurrence of the Omicron variant of SARS-CoV-2 in northern Viet Nam in early 2022.

The Omicron variant caused a surge of infections with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in Viet Nam in early 2022, signalling community transmission. We report on active whole-genome sequencing surveillance of positive SARS-CoV-2 samples collected at that time in northern Viet Nam from international arrivals and community clusters. We used an amplicon protocol developed with 14 polymerase chain reaction products and the Illumina iSeq 100 platform. Overall, 213 nasopharyngeal or throat swabs were analysed, of which 172 samples were identified with the Omicron variant. Of these, 80 samples were collected from community cases in February 2022, among which 59 samples were sublineage BA.2 and one sample was the recombinant XE variant. Our results indicated that Omicron had replaced Delta as the dominant variant in a very short period of time and that continuously conducting active whole-genome sequencing surveillance is necessary in monitoring the evolution and genomic diversity of SARS-CoV-2 in Viet Nam.

Molecular characterization of bovine foamy virus and its association with bovine leukemia virus infection in Vietnamese cattle.

The detection of bovine foamy virus (BFV) in Vietnamese cattle was performed using conventional PCR targeting pol and gag genes. Out of 243 tested samples, ten (4.1%) and eight (3.3%) samples were positive for BFV gag and pol DNA, respectively. The prevalence of bovine leukemia virus (BLV) estimated by detection of proviral DNA using nested PCR targeting env gene was 26.7% (65/243). The results of nucleotide sequence alignment and the phylogenetic analysis suggested that Vietnamese BFV strains showed high homology to isolates belonging to either European or non-European clades. There was no significant correlation between BLV and BFV. This study provides information regarding BFV infection and confirms the existence of two BFV clades among Vietnamese cattle for the first time.

Virological characteristics of cases of COVID-19 in northern Viet Nam, January-May 2020.

Background: Viet Nam confirmed its first case of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection on 23 January 2020 among travellers from Wuhan, China, and experienced several clusters of community transmission until September. Viet Nam 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 Viet Nam. Methods: Between January and May 2020, 15 650 upper respiratory tract specimens were collected from 14 470 suspected cases and contacts in northern Viet Nam. All were tested for SARS-CoV-2 by real-time RT-PCR. Individuals with positive specimens were tested every three days until two tests were negative. 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%) had negative results after two tests, while 11 and 4 still tested positive when sampled a third and fourth time, respectively. SARS-CoV-2 was isolated from 29 of 81 specimens (36%) with a cycle threshold (Ct) value < 30. Seven patients who tested positive again after testing negative had Ct values > 30 and negative cultures. Conclusion: Early, widespread testing for SARS-CoV-2 in northern Viet Nam 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 after clearance. Large-scale molecular diagnostic testing is a critical part of early detection and containment of COVID-19 in Viet Nam and will remain necessary until vaccination is widely implemented.

Detection and genotyping of bovine leukemia virus (BLV) in Vietnamese cattle.

Bovine leukemia virus (BLV) belongs to the genus, Deltaretrovirus of the family, Retroviridae and it is the causative agent of enzootic bovine leukosis. The prevalence of BLV in three provinces in the Red River Delta Region in the North of Vietnam, Hanoi, Vinhphuc and Bacninh was studied from April 2017 to June 2018. A total of 275 blood samples collected from cattle were used for serum isolation and DNA extraction. Of these samples, 266 sera were subjected to ELISA test for detecting antibody against BLV gp51 protein and 152 DNA samples were used to detect the 444 bp fragment corresponding to a part of the gp51 region of the env by nested PCR. The results showed that 16.5% (n=44) and 21.1% (n=32) of samples were positive for BLV gp51 antibody and BLV proviral DNA, respectively. Phylogenetic analysis of the partial (423 bp) and complete (913 bp) BLV env-gp51 gene indicated that Vietnamese strains were clustered into genotypes 1, 6 and 10 (G1, G6 and G10). Of those genotypes, G1 genotype was dominant; G6 strains were designated as G6e and G6f subgenotypes; the existence of genotype 10 was confirmed for the first time in Vietnam. The present study provides important information regarding the prevalence of BLV infection and genetic characteristics of BLV strains identified in Vietnam, contributing to promote the establishment of disease control and eradication strategies in Vietnam.

Viral co-infections among children with confirmed measles at hospitals in Hanoi, Vietnam, 2014.

OBJECTIVE: To characterize viral co-infections among representative hospitalized measles cases during the 2014 Hanoi outbreak. METHODS: Throat swabs were collected from 54 pediatric patients with confirmed measles, and molecular diagnostics performed for 10 additional viral respiratory pathogens (Influenza A/H1N1pdm09; A/H3N2 and influenza B; Parainfluenza 1, 2, 3; Respiratory Synctial Virus, RSV; human Metapneumovirus, hMPV; Adenovirus and Picornavirus). RESULTS: Twenty-one cases (38.9%) showed evidence of infection with other respiratory viruses: 15 samples contained measles plus one additional virus, and 6 samples contained measles plus 2 additional viruses. Adenovirus was detected as a predominant cause of co-infections (13 cases; 24.1%), followed by RSV (6 cases; 11.1%), A/H1N1pdm09 (3 cases; 5.6%), PIV3 (3 cases; 3.7%), Rhinovirus (3 cases; 3.7%) and hMPV (1 case; 1.96%). CONCLUSIONS: Viral co-infections identified from pediatric measles cases may have contributed to increased disease severity and high rate of fatal outcomes. Optimal treatment of measles cases may require control of multiple viral respiratory pathogens.

Surveillance of Severe Acute Respiratory Infection (SARI) for Hospitalized Patients in Northern Vietnam, 2011-2014.

Severe acute respiratory infections (SARI) are leading causes of hospitalization, morbidity, and mortality in children worldwide. The aim of this study was to identify viral pathogens responsible for SARI in northern Vietnam in the period from 2011 to 2014. Throat swabs and tracheal aspirates were collected from SARI patients according to WHO guidelines. The presence of 13 different viral pathogens (influenza A[H1N1]pdm09; A/H3N2; A/H5; A/H7 and B; para influenza 1,2,3; RSV; HMPV; adeno; severe acute respiratory syndrome-CoV and rhino) was tested by conventional/real-time reverse transcription-polymerase chain reaction. During the study period, 975 samples were collected and tested. More than 30% (32.1%, 313 samples) of the samples showed evidence of infection with influenza viruses, including A/H3N2 (48 samples), A (H1N1) pdm09 (221 samples), influenza B (42 samples), and co-infection of A (H1N1) pdm09 or A/H3N2 and influenza B (2 samples). Other respiratory pathogens were detected in 101 samples, including rhinovirus (73 samples), adenovirus (10 samples), hMPV (9 samples), parainfluenza 3 (5 samples), parainfluenza 2 (3 samples), and RSV (1 sample). Influenza A/H5, A/H7, or SARS-CoV were not detected. Respiratory viral infection, particularly infection of influenza and rhinoviruses, were associated with high rates of SARI hospitalization, and future studies correlating the clinical aspects are needed to design interventions, including targeted vaccination.