Impact of dengue virus (DENV) co-infection on clinical manifestations, disease severity and laboratory parameters.

Amreeta Dhanoa,Chin Fang Ngim,Ganeswrie Rajasekaram,Wilhelm Wei Han Eng,Nur Amelia Azreen Adnan,Han Ming Gan,Sharifah Syed Hassan,Chun Fatt Lau,Teik Seng Chan

doi:10.1186/s12879-016-1731-8

Abstract

BackgroundThe co-circulation of 4 DENV serotypes in geographically expanding area, has resulted in increasing occurrence of DENV co-infections. However, studies assessing the clinical impact of DENV co-infections have been scarce and have involved small number of patients. This study explores the impact of DENV co-infection on clinical manifestations and laboratory parameters.MethodsThis retrospective study involved consecutive hospitalized patients with non-structural protein 1 (NS1) antigen positivity during an outbreak (Jan to April 2014). Multiplex RT-PCR was performed directly on NS1 positive serum samples to detect and determine the DENV serotypes. All PCR-positive serum samples were inoculated onto C6/36 cells. Multiplex PCR was repeated on the supernatant of the first blind passage of the serum-infected cells. Random samples of supernatant from the first passage of C6/36 infected cells were subjected to whole genome sequencing. Clinical and laboratory variables were compared between patients with and without DENV co-infections.ResultsOf the 290 NS1 positive serum samples, 280 were PCR positive for DENV. Medical notes of 262 patients were available for analysis. All 4 DENV serotypes were identified. Of the 262 patients, forty patients (15.3 %) had DENV co-infections: DENV-1/DENV-2(85 %), DENV-1/DENV-3 (12.5 %) and DENV-2/DENV-3 (2.5 %). Another 222 patients (84.7 %) were infected with single DENV serotype (mono-infection), with DENV- 1 (76.6 %) and DENV- 2 (19.8 %) predominating. Secondary dengue infections occurred in 31.3 % patients. Whole genome sequences of random samples representing DENV-1 and DENV-2 showed heterogeneity amongst the DENVs.Multivariate analysis revealed that pleural effusion and the presence of warning signs were significantly higher in the co-infected group, both in the overall and subgroup analysis. Diarrhoea was negatively associated with co-infection. Additionally, DENV-2 co-infected patients had higher frequency of patients with severe thrombocytopenia (platelet count < 50,000/mm3), whereas DENV-2 mono-infections presented more commonly with myalgia. Elevated creatinine levels were more frequent amongst the co-infected patients in univariate analysis. Haemoconcentration and haemorrhagic manifestations were not higher amongst the co-infected patients. Serotypes associated with severe dengue were: DENV-1 (n = 9), DENV-2 (n = 1), DENV-3 (n = 1) in mono-infected patients and DENV-1/DENV-2 (n = 5) and DENV-1/DENV-3 (n = 1) amongst the co-infected patients.ConclusionDENV co-infections are not uncommon in a hyperendemic region and co-infected patients are skewed towards more severe clinical manifestations compared to mono-infected patients.

Highlights

The co-circulation of 4 Dengue virus (DENV) serotypes in geographically expanding area, has resulted in increasing occurrence of DENV co-infections
DENV serotypes were determined by multiplex RT-PCR directly from original serum samples and from the supernatant of the first passage of C6/36 serum infected cells
In conclusion, our findings suggest that DENV co-infections are not a rare occurrence and may play a previously unrecognized role in the pathogenesis, virulence and clinical expression of disease

Summary

Introduction

The co-circulation of 4 DENV serotypes in geographically expanding area, has resulted in increasing occurrence of DENV co-infections. Dengue virus (DENV) infection is a global health threat, with approximately half of the world’s population at risk of being infected and 0.5 million people requiring hospitalization each year [1] It is amongst the most important vector-borne viral disease of humans. The co-circulation of multiple DENV serotypes in the same region, invariably facilitates the occurrence of co-infections with rates ranging from 5 % to 30 % [8,9,10,11,12,13,14,15] to as high as 40 % to 50 % [16, 17] This phenomenon has heightened the importance of understanding the role of co-infections in the clinical outcome of disease. Vast majority of these studies were descriptive in nature and the numbers of co-infections were rather small to reach valid statistical conclusions

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