H.T.Pham[1]*, N.H.Tran [1,2], Q.D.Ha[1,2], D.K.Tran[1,2], V.H.Pham[1,3]
[1] Vietnam Research and Development Institute of Clinical Microbiolgy, Vietnam
[2] Nam Khoa Biotek Co. Ltd., Vietnam
[3] Phan Chau Trinh University, Vietnam

Background

Dengue hemorrhagic fever (DHF) is currently the most widespread and rapidly increasing vector-borne disease globally, with symptoms ranging from mild to severe and, in some cases, fatal. Vietnam, especially Quang Nam province, is an endemic region for DHF with a hot and humid tropical climate. Due to the limited availability of advanced surveillance facilities, there are very few epidemiological and microbiological reports on Dengue virus (DENV) serotypes in this region.

Aims of the study

We pursued two primary objectives: (1) to investigate the circulating Dengue virus serotypes in blood samples of suspected patients with DHF, from 2020 to 2022, and compare the results with published data from 2018 of the same study population, and (2) to determine whether repeat infections lead to severe outcomes.

Materials and methods

Blood samples were obtained from patients clinically diagnosed with DHF and admitted to Quang Nam General Hospital from 2020 to 2022. The samples were centrifuged to separate blood plasma, from which RNA was extracted using the ^NKDNA/RNAprep MAGBEAD kit. Multiplex Reverse Transcription real-time Polymerase Chain Reaction (MLP RT-rPCR) was then conducted for Dengue virus (DENV) detection and serotype identification. We analyzed the data and compared with data from 2018. Subsequently, positive samples were selected for Enzyme-Linked Immunosorbent Assay (ELISA) to assess the presence of IgG.

Results and discussions

A total of 1179 samples were included in the study, comprising 122 samples in 2020-2021 and 1057 samples in 2022. In the 2020-2021 period, DENV2 emerged as the most prevalent serotype, accounting for 57.38% (70/122). DENV4 was identified in 7.38% of the samples (9/122), while DENV1 was detected in 5 samples (4.10%). In 2022, a notable spike was observed in the prevalence of DENV1. reaching 35% (370/1057), followed by DENV2 at 29.71% (314/1057). DENV4 constituted a small share of 3.78% (50/1057). Importantly, our findings diverged from data of 2018, where DENV4 dominated at 68.5%, and DENV1 and DENV2 each constituted shares of less than 20%. This suggests significant shifts in the distribution of viral serotypes over the years. 214 positive samples were selected for ELISA, 103 of which exhibited the presence of IgG (48.14%), indicating prior DENV infections.

Conclusions

Our study is one of the few conducted in Quang Nam province on Dengue virus serotypes. Over the years, there are major shifts in the distribution of DENV serotypes, emphasizing the need for advanced surveillance for predicting and preventing further DHF epidemics. Additionally, the elevated presence of IgG in the blood samples of hospitalized patients suggests potential severe outcomes resulting from recurrent DENV infections, possibly influenced by antibody-dependent enhancement

Keywords: Denge hemorrhagic fever, Dengue virus serotypes; RT-rPCR